A device for rapidly detecting trace iron ion content in water

Abstract

The application relates to the technical field of water quality analysis and detection, and discloses a device for rapidly detecting the content of trace iron ions in water, which comprises a machine box, a luminescence dish arranged in the machine box, a photomultiplier arranged at a light measuring position of the luminescence dish, a negative high-voltage power supply for supplying power to the photomultiplier, a dosing mechanism and a controller. The luminescence dish is used for accommodating a water sample to be measured and receiving reagents added by the dosing mechanism; the water sample to be measured and the reagents are mixed in the luminescence dish and induce chemical luminescence; and the photomultiplier is used for receiving the chemical luminescence in the luminescence dish. By matching a fixed-gain amplifier with a fixed amplification multiple with a reference light source with controlled luminescence intensity, the full-scale calibration is borne by the output voltage of the negative high-voltage power supply, the gain difference of the photomultiplier between different channels and over time is compensated, and the whole calibration can be completed by only one chemical luminescence of a standard solution.

Description

Technical Field

[0001] This invention relates to the field of water quality analysis and testing technology, specifically to a device for rapidly detecting trace iron ion content in water. Background Technology

[0002] Iron content in water is a crucial indicator of the quality of boiler feedwater, steam, and condensate. In the thermal systems of thermal power plants, nuclear power plants, and steam turbine ships, trace amounts of iron carried by feedwater can deposit on heated surfaces, exacerbating metal corrosion and scaling, thus threatening the safe operation of boilers and turbines. Similarly, in pharmaceutical and semiconductor industries, where ultrapure water quality requirements are stringent, the iron content in the water must be controlled at extremely low levels. The iron content measured in these applications is often as low as micrograms per liter, placing high demands on the sensitivity of the detection methods and the stability of the detection equipment.

[0003] Currently, power plants widely use the spectrophotometric method specified in GB / T14427. This method requires manually adding acid and boiling the water sample before measurement to convert the iron in the sample into a form suitable for colorimetric measurement. The boiling step itself is time-consuming, and continuous operation on-site requires specialized heating and cooling equipment. The acid-adding and boiling operations demand skilled personnel and advanced equipment, making the entire process cumbersome and difficult to automate unattended. Therefore, this method, reliant on boiling water, is inconvenient for continuous on-site monitoring and is often only suitable for intermittent analysis in laboratories.

[0004] The luminol chemiluminescence method is suitable for the determination of trace amounts of iron due to its high sensitivity and eliminates the need for pretreatment such as acid addition and boiling, making it more suitable for field needs. This method utilizes the light emitted when luminol is oxidized and the enhancement effect of ferrous ions on the luminescence to determine the iron content by measuring the luminescence intensity. However, for a long time, this method has mostly remained in the stage of manual operation in the laboratory or step-by-step completion using discrete instruments. The addition of reagents, luminescence, photometry, and data processing are scattered across different instruments, and the measurement results depend on the operator's experience. It has always been difficult to integrate this method into a dedicated instrument that can automatically complete the measurement simply by turning on the instrument and connecting the reagents, and therefore it is difficult to undertake the task of continuous online monitoring of thermal systems.

[0005] To automate chemiluminescence immunoassay, the precise, micro-quantitative addition of reagents is paramount. Traditionally, this step relied on peristaltic or plunger pumps. However, peristaltic pumps have pulsating outputs, their tubing is prone to fatigue and aging, and replacement of the tubing alters the repeatability of the metering. Furthermore, different reagents can contaminate each other over long-term operation. Plunger pumps, on the other hand, are susceptible to corrosion from strong acids and bases, as well as the jamming of tiny particles. Once the seals wear down, the metering accuracy gradually declines. In applications requiring long-term unattended operation and repeated micro-quantification, the accuracy and consistency of these pumping methods are difficult to maintain in the long run.

[0006] The introduction and quantification of the water sample itself also affect the measurement results. In the past, the volume of water sample in the luminescent dish was controlled by using a drain solenoid valve in conjunction with a liquid level detector. However, under small pressure differences, air bubbles are easily trapped at the valve orifice of the solenoid valve, forming air emboli, which leads to poor drainage and inaccurate volume. When measuring extremely low iron content, the water sample remaining in the luminescent dish and pipeline from the previous measurement can cause significant cross-contamination in the current measurement. If it cannot be effectively replaced, the reading will deviate from the true value.

[0007] The challenges persisted even in the signal acquisition stage. The light generated in the luminescent dish was inherently weak and required conversion and amplification by a photomultiplier tube (PMT) for measurement. However, the gain of the PMT varied with the supply voltage and was highly sensitive to environmental magnetic fields, including the Earth's magnetic field. Gain differences and drifts occurred between different PMTs and even within the same PMT over long-term use. To ensure consistent readings from all devices, full-scale calibration was necessary before measurement. Traditional methods involved repeatedly preparing and measuring standard solutions and adjusting the amplification factor based on experience, which was time-consuming and difficult to automate in online operation. Furthermore, if the interference of the magnetic field on the PMT was not suppressed, the readings would fluctuate accordingly. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a device for the rapid detection of trace iron ion content in water. It solves the problems of luminol chemiluminescence method, which has long been limited to manual laboratory operation or step-by-step measurements using discrete instruments, making it difficult to develop a dedicated instrument that can automatically complete measurements upon reagent connection. Existing peristaltic pump and plunger pump dosing methods suffer from pulsation, pump tube aging, corrosion, jamming, and reagent contamination, making it difficult to maintain the accuracy and consistency of trace reagent measurements over a long period. When using a drain solenoid valve to quantify water samples, air embolisms can easily form under small pressure differences, leading to inaccurate quantification. Furthermore, residual water samples from previous measurements in the luminescent dish and tubing can cause cross-contamination in the current measurement. Additionally, the gain of photomultiplier tubes is affected by the power supply voltage and environmental magnetic fields, including the Earth's magnetic field, resulting in differences and drift between different photomultiplier tubes and over long-term use. Traditional full-scale calibration requires repeated measurements of standard solutions and manual adjustments, making it difficult to automate in unattended online operation.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a device for rapidly detecting trace iron ion content in water, comprising a chassis, a light-emitting dish disposed within the chassis, a photomultiplier tube disposed at the photometric position of the light-emitting dish, a negative high-voltage power supply for powering the photomultiplier tube, a dosing mechanism, and a controller; the light-emitting dish is used to contain the water sample to be tested and to receive the reagent added by the dosing mechanism, the water sample to be tested and the reagent are mixed in the light-emitting dish and induce chemiluminescence, the photomultiplier tube is used to receive the chemiluminescence in the light-emitting dish; the chassis also includes a fixed-gain amplifier and a reference light source, the output end of the photomultiplier tube is electrically connected to the controller via the fixed-gain amplifier, the reference light source is electrically connected to the controller and its luminous intensity is controlled by the controller, the reference light source emits reference light and couples it to the photosensitive surface of the photomultiplier tube, the controller is electrically connected to the negative high-voltage power supply; when the light-emitting dish does not produce chemiluminescence, the controller illuminates the reference light source and adjusts the output voltage of the negative high-voltage power supply to align the output of the fixed-gain amplifier to a preset full-scale target value, thereby completing the full-scale calibration.

[0010] Iron detection is based on luminol chemiluminescence. Luminol is oxidized under alkaline conditions to generate an excited-state product that emits blue light. Ferrous ions (Fe2+) in this oxidation-luminescence system enhance the luminescence, with the intensity increasing with the concentration of Fe2+ ions. This light is then converted into an electrical signal by a photomultiplier tube for measurement. Since only Fe2+ ions contribute to the enhancement, Fe3+ ions must be reduced to Fe2+ ions before measuring total iron. Furthermore, because water samples may contain colloidal iron and solid particulate iron in addition to dissolved iron, this device measures iron that participates in the chemiluminescence reaction in its dissolved state—that is, soluble iron.

[0011] The chemiluminescence signal generated within the luminescent dish is weak, and the gain of the photomultiplier tube varies between different measurement channels and changes over time. Therefore, full-scale calibration is required before measurement. This invention uses a fixed-gain amplifier with a fixed amplification factor, meaning the amplification factor remains constant during calibration and measurement. A reference light source provides a controlled-intensity reference light when the luminescent dish is not generating chemiluminescence. The gain of the photomultiplier tube is adjusted by regulating the output voltage of the negative high-voltage power supply, aligning the output of the fixed-gain amplifier to the target full-scale value. Accordingly, full-scale calibration is handled by the output voltage of the negative high-voltage power supply, unifying the full-scale values ​​across measurement channels. Gain differences in the photomultiplier tube between channels and over time are compensated by the output voltage of the negative high-voltage power supply.

[0012] Preferably, the photomultiplier tube is fitted with an inner magnetic shield, which is then fitted with an outer magnetic shield, with a gap between the inner and outer shields. The reference light source is positioned within this gap, and the reference light emitted by the reference light source is coupled to the photosensitive surface of the photomultiplier tube via an optical fiber through the inner magnetic shield. The photomultiplier tube is sensitive to magnetic fields; ambient magnetic fields, including the Earth's magnetic field, alter its gain when acting on it. Positioning the reference light source within the gap between the two magnetic shields provides reference light to the photosensitive surface without disrupting the inner magnetic shield's coverage of the photomultiplier tube.

[0013] Preferably, both the inner and outer magnetic shields are made of soft magnetic low-carbon steel. The inner magnetic shield is circular, and the outer magnetic shield is square. The inner magnetic shield is electrically connected to the shielding wire for photocurrent output, and the outer magnetic shield is electrically connected to the chassis. The circular shape of the inner magnetic shield matches the shape of the photomultiplier tube, while the square shape of the outer magnetic shield facilitates assembly with the chassis. The soft magnetic low-carbon steel has high permeability, and the two magnetic shields provide two levels of shielding for the magnetic field. The electrical connection between the inner magnetic shield and the shielding wire for photocurrent output provides electrical shielding against the weak photocurrent output by the photomultiplier tube, while the electrical connection between the outer magnetic shield and the chassis forms an outer electrical shield. The magnetic shielding and electrical shielding are achieved by the same structure.

[0014] Preferably, the reference light source is a blue light-emitting diode, and the emission center wavelength of the blue light-emitting diode matches the emission center wavelength of the chemiluminescence reaction in the light-emitting dish, so that the spectral response of the reference light on the photosensitive surface corresponds to the spectral response of the chemiluminescence in the light-emitting dish on the photosensitive surface.

[0015] Preferably, the full-scale target value is 90% of the full-scale value of the measurement range of the fixed gain amplifier, so that after full-scale alignment, the measurement output is within the linear range of the fixed gain amplifier and the negative high-voltage power supply with a margin.

[0016] Preferably, the full-scale calibration includes: controlling the addition of a standard solution to the luminescent dish via the controller, and controlling the dosing mechanism to add reagents to the luminescent dish to induce chemiluminescence; measuring the output U1 of the fixed-gain amplifier corresponding to the chemiluminescence peak when the output voltage of the negative high-voltage power supply is V1; adjusting the luminescence intensity of the reference light source when the luminescent dish is not producing chemiluminescence, so that the output of the fixed-gain amplifier is equal to U1; keeping the luminescence intensity of the reference light source constant, increasing the output voltage of the negative high-voltage power supply from V1 to V2, so that the output of the fixed-gain amplifier increases from U1 to the full-scale target value; and determining V2 as the operating output voltage of the negative high-voltage power supply. In this way, the reference light source generates a reference light with the same intensity as the luminescence of the standard solution, and the subsequent full-scale adjustment is completed based on this reference light when the luminescent dish is not producing chemiluminescence, thus completing the full-scale calibration with only one chemiluminescence of the standard solution.

[0017] Preferably, the dosing mechanism includes a negative pressure air pump, a positive pressure air pump, a metering pipeline, and a liquid level sensor disposed on the metering pipeline. One end of the metering pipeline is connected to the reagent bottle, and the other end is connected to the luminescent dish. The negative pressure air pump is connected to the metering pipeline and is used to create a negative pressure within the metering pipeline. The positive pressure air pump is connected to the metering pipeline and is used to create a positive pressure within the metering pipeline. The liquid level sensor is electrically connected to the controller. The controller controls the negative pressure air pump to lift the reagent from the reagent bottle into the metering pipeline, causing the liquid level in the metering pipeline to rise. When the liquid level reaches the liquid level sensor, the controller controls the negative pressure air pump to stop. After the negative pressure air pump stops, its motor continues to rotate due to inertia, causing the liquid level in the metering pipeline to pass the liquid level sensor. Subsequently, the liquid level that has passed the liquid level sensor is released back down, and the reagent is determined to be metered when the liquid level passes the liquid level sensor again. After metering is complete, the controller controls the positive pressure air pump to add the reagent from the metering pipeline into the luminescent dish. When the negative pressure air pump stops, the liquid level rises due to the motor inertia. This is eliminated after the pressure is released and the liquid level returns to normal. The reagent measurement is based on the second time the liquid level passes the liquid level sensor, thus improving the repeatability of reagent measurement.

[0018] Preferably, the volume of the luminescent dish is 12mL-18mL, the luminescent dish is connected to a water inlet pipe and a water outlet pipe, the luminescent dish is provided with a siphon tube, the inlet of the siphon tube is located inside the luminescent dish and the height of its opening corresponds to the set volume of the water sample to be tested in the luminescent dish, the siphon tube is used to discharge the water sample to be tested that is higher than the set volume in the luminescent dish, and a water flow sensor is provided on the tube body of the siphon tube, the water flow sensor is electrically connected to the controller and is used to detect the water flow in the siphon tube. Because the inlet pipe often draws in air during the water intake process, which can easily cause false alarms from the sensor, the water flow sensor is installed on the siphon tube. The water flow within the siphon tube is used as the criterion: the controller controls the water sample to be tested to be introduced into the luminescent dish through the inlet pipe. When the water flow sensor detects the water flow in the siphon tube for the first time, it indicates that the luminescent dish is full and siphoning has begun. Subsequently, the controller controls the luminescent dish to be emptied through the drain pipe to soak and rinse it. Then, the controller controls the water sample to be tested to be introduced into the luminescent dish through the inlet pipe again. When the water flow sensor detects the water flow in the siphon tube for the second time, and the flow changes from detected to undetectable, it indicates that the siphoning process is complete, and the luminescent dish retains the set volume of water sample to be tested. This process of first soaking, rinsing, and emptying with the water sample to be tested, and then introducing and quantitatively siphoning the water sample to be tested, ensures that the water sample remaining in the luminescent dish and pipe from the previous measurement is replaced by the current water sample, reducing cross-contamination between measurements.

[0019] Preferably, the reagent includes an oxidant, a reducing agent, and a luminescent agent. The oxidant is a solution containing potassium periodate or potassium iodate, the reducing agent is a solution containing sodium bisulfite, and the luminescent agent is an alkaline solution of luminol. The controller controls the dosing mechanism to add reagents to the luminescent dish in the following order: first, a reducing agent is added to the luminescent dish, and air is introduced into the dish to stir the reducing agent and the water sample to be tested. After standing, the ferric ions in the water sample are reduced to ferrous ions. Then, an oxidant is added to the luminescent dish. Finally, the luminescent agent is added to the luminescent dish to initiate chemiluminescence. The oxidant is used to oxidize luminol, the sodium bisulfite in the reducing agent is used to reduce ferric ions to ferrous ions without introducing iron ions into the water sample, and the luminescent agent is an alkaline solution carrying luminol. The addition of the reducing agent, followed by stirring with air and standing, ensures that the iron in the water sample exists as ferrous ions before the addition of the luminescent agent, and the addition of the luminescent agent initiates chemiluminescence.

[0020] Preferably, the controller controls the dosing mechanism to add only an oxidant and a luminescent agent to the first water sample to be tested, triggering chemiluminescence and obtaining a first luminescence amount corresponding to the soluble ferrous iron content; the controller also controls the dosing mechanism to add a reducing agent, an oxidant, and a luminescent agent to the second water sample to be tested, triggering chemiluminescence and obtaining a second luminescence amount corresponding to the soluble total iron content; and the soluble ferric iron content is obtained by the difference between the soluble total iron content and the soluble ferrous iron content. When no reducing agent is added to the first water sample to be tested, only the existing ferrous ions in it trigger luminescence; when a reducing agent is added to the second water sample to be tested, the ferric ions are reduced to ferrous ions and together with the existing ferrous ions, trigger luminescence, corresponding to the soluble total iron content. The correspondence between the luminescence amount and the content is determined in advance by measuring a standard solution with a known content, and the soluble ferrous iron content and the soluble total iron content are calculated accordingly, and the soluble ferric iron content is obtained by the difference between the two.

[0021] This invention provides a device for rapidly detecting trace iron ion content in water. It has the following beneficial effects: 1. This invention combines a fixed-gain amplifier with a controlled-intensity reference light source. Before the luminescent dish produces chemiluminescence, the reference light source reproduces a light source with the same intensity as the standard solution. Then, the output voltage of the negative high-voltage power supply is adjusted to align the output of the fixed-gain amplifier to the full-scale target value. This allows the full-scale calibration to be handled by the output voltage of the negative high-voltage power supply, compensating for gain differences in different channels of the photomultiplier tube and those occurring over time. The entire calibration can be completed with just one chemiluminescence test of the standard solution. Simultaneously, a circular inner antimagnetic shield and a square outer antimagnetic shield, both made of soft magnetic low-carbon steel and connected to the shielded wires of the photocurrent output and the chassis, are sequentially fitted around the photomultiplier tube. This shields the ambient magnetic field and electric field through the same structure, preventing fluctuations in the photomultiplier tube's gain due to magnetic or electric field interference, thus ensuring measurement accuracy and consistency.

[0022] 2. This invention utilizes a negative pressure air pump to extract the reagent and a positive pressure air pump to add the reagent. It takes advantage of the phenomenon where the liquid level exceeds the level sensor due to the motor's inertia after the air pump stops. The liquid level is then slowly lowered by depressurization, and the second passage of the liquid level sensor is used as the criterion for accurate measurement, eliminating the over-rush error caused by inertia. Simultaneously, the water flow sensor is placed on the siphon tube rather than the inlet pipe, avoiding false alarms caused by air intake during water intake. The luminescent dish is first filled with the water sample to be tested, then emptied by the siphon overflow for immersion and rinsing. After refilling, a set volume, dependent only on the height of the siphon opening, is retained. Therefore, the measurement of trace reagents remains consistent over a long period. Residue from the previous measurement is replaced by the current water sample, reducing cross-contamination, making it particularly suitable for measuring water samples with extremely low iron content.

[0023] 3. This invention distinguishes between water samples with and without the addition of a reducing agent. The luminescence measured without the reducing agent corresponds to the soluble ferrous iron content, while the luminescence measured after reducing ferric ions with the reducing agent corresponds to the soluble total iron content. Subtracting the two yields the soluble ferric iron content. Therefore, a single device can provide the valence distribution of iron in water, and the entire process does not require boiling the water sample with acid, allowing for long-term unattended online operation. Attached Figure Description

[0024] Figure 1 This is a front view of the chassis in this invention; Figure 2 This is a rear view of the chassis in this invention; Figure 3 This is a side sectional view of the chassis in this invention; Figure 4 This is a schematic diagram of the front structure of the light-emitting dish in this invention; Figure 5 This is a schematic diagram of the chemical flow path composition of the present invention.

[0025] The components include: 1. Chassis; 2. Light-emitting dish; 3. Photomultiplier tube; 4. Negative high-voltage power supply; 5. Fixed gain amplifier; 6. Reference light source; 7. Inner anti-magnetic shield; 8. Outer anti-magnetic shield; 9. Negative pressure air pump; 10. Positive pressure air pump; 11. Metering pipeline; 12. Liquid level sensor; 13. Siphon tube; and 14. Water flow sensor. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see the appendix Figure 1 -Appendix Figure 5 This invention provides a device for rapidly detecting trace iron ion content in water, used to measure the iron content in water from boiler feedwater, steam, and condensate in thermal power plants, as well as in nuclear power plants, steam turbine ships, and pharmaceutical and semiconductor ultrapure water applications. The device's detection is based on luminol chemiluminescence. Luminol is oxidized by an oxidant under alkaline conditions to generate an excited state of the 3-aminophthalic acid anion. This excited state emits blue light with a center wavelength of 410 nm when it returns to the ground state. Ferrous ions (Fe2+) enhance the luminescence in this oxidation-luminescence system; the luminescence intensity increases with increasing Fe2+ ion content, and the luminescence intensity corresponds to the Fe2+ ion content.

[0028] In the aforementioned luminescent system, ferrous ions (Fe2+) enhance luminescence, while ferric ions (Fe3+) do not. For water samples containing both ferrous and ferric ions, when measuring their total iron content, the ferric ions in the water sample are first reduced to ferrous ions, ensuring that all iron in the water sample participates in luminescence as ferrous ions. Then, chemiluminescence is initiated and measured.

[0029] Since the water sample to be tested may contain colloidal iron and solid particulate iron in addition to dissolved iron, and the iron that participates in the above-mentioned chemiluminescence reaction is iron that exists in dissolved state, the object measured by this device is soluble iron, which is correspondingly divided into soluble ferrous iron, soluble total iron and soluble ferric iron.

[0030] Currently, power plants widely use the spectrophotometric method specified in GB / T14427. This method requires manual acid addition and boiling of the water sample before measurement to convert the iron in the water sample into a form that is easier to measure colorimetrically. The boiling operation is time-consuming, and in continuous on-site monitoring, a dedicated heating and cooling device is also required, making it difficult to automate in unattended situations. This device is based on luminol chemiluminescence, which eliminates the need for acid addition and boiling of the water sample. It integrates reagent addition, chemiluminescence, light signal acquisition, full-scale calibration, and content calculation into the unit 1. After the reagent is connected, the controller automatically completes the measurement.

[0031] The device for rapid detection of trace iron ion content in water includes a housing 1, a light-emitting dish 2 housed in the housing 1, a photomultiplier tube 3, a negative high-voltage power supply 4, a fixed gain amplifier 5, a reference light source 6, a dosing mechanism, and a controller.

[0032] The luminescent dish 2 is located inside the housing 1 and is used to hold the water sample to be tested and receive the reagent added by the dosing mechanism. The water sample and the reagent are mixed in the luminescent dish 2, triggering chemiluminescence. The dosing mechanism is connected to the reagent bottle and the luminescent dish 2, and is used to quantitatively add reagent to the luminescent dish 2 under the control of the controller.

[0033] A photomultiplier tube 3 is positioned at the photometric position of the light-emitting dish 2, with its photosensitive surface facing the dish 2. It is used to receive the chemiluminescence generated within the dish 2 and convert it into photocurrent. A negative high-voltage power supply 4 is electrically connected to the photomultiplier tube 3 to supply power to it. The gain of the photomultiplier tube 3 increases as the output voltage of the negative high-voltage power supply 4 increases.

[0034] The output terminal of photomultiplier tube 3 is electrically connected to the controller via fixed gain amplifier 5. The amplification factor of fixed gain amplifier 5 is fixed, that is, during full-scale calibration and measurement, the amplification factor of fixed gain amplifier 5 remains unchanged. The photocurrent output by photomultiplier tube 3 is converted and amplified into a voltage signal by fixed gain amplifier 5 and then output to the controller.

[0035] The reference light source 6 is electrically connected to the controller. The luminous intensity of the reference light source 6 is controlled by the controller. The reference light source 6 emits reference light and couples it to the photosensitive surface of the photomultiplier tube 3. The controller is connected to the negative high-voltage power supply 4, the fixed-gain amplifier 5, the reference light source 6, and the dosing mechanism. It is used to control the dosing mechanism to add drugs, control the light emission of the reference light source 6, adjust the output voltage of the negative high-voltage power supply 4, and receive the electrical signal output by the fixed-gain amplifier 5 to obtain the iron content.

[0036] The chemiluminescence signal generated in the luminescent dish 2 is weak, and the gain of the photomultiplier tube 3 varies between different measurement channels and changes over time. To ensure accurate and consistent measurement results, the full-scale output of the fixed-gain amplifier 5 is calibrated before measurement.

[0037] In this invention, the full-scale calibration is performed by the output voltage of the negative high-voltage power supply 4. The amplification factor of the fixed-gain amplifier 5 remains constant. When the light-emitting dish 2 does not produce chemiluminescence, the controller illuminates the reference light source 6. The reference light source 6 provides a reference light with controlled luminescence intensity to the photosensitive surface of the photomultiplier tube 3, and adjusts the output voltage of the negative high-voltage power supply 4 to change the gain of the photomultiplier tube 3, so that the output of the fixed-gain amplifier 5 is aligned with the preset full-scale target value, thereby completing the full-scale calibration.

[0038] After the reagent is connected, the device controls the dosing mechanism to add the reagent to the luminescent dish 2 according to the set timing sequence, which triggers chemiluminescence. The photomultiplier tube 3 and fixed gain amplifier 5 collect the luminescence signal. The controller obtains the soluble iron content in the water sample to be tested based on the collected luminescence signal, thus completing the entire measurement process from dosing, chemiluminescence, signal acquisition to content calculation within the casing 1.

[0039] In this embodiment, the optical signal acquisition and full-scale calibration system includes a photomultiplier tube 3, a fixed gain amplifier 5, a negative high-voltage power supply 4, a reference light source 6, and a controller.

[0040] The photosensitive surface of the photomultiplier tube 3 faces the photometric position of the light-emitting dish 2. The chemiluminescence generated in the light-emitting dish 2 is incident through the photosensitive surface, converted into photocurrent by the photomultiplier tube 3, and multiplied for output. The dynode of the photomultiplier tube 3 is powered by the negative high-voltage power supply 4, and the gain of the photomultiplier tube 3 increases with the increase of the output voltage of the negative high-voltage power supply 4.

[0041] The output terminal of photomultiplier tube 3 is connected to the input terminal of fixed gain amplifier 5. Fixed gain amplifier 5 converts and amplifies the photocurrent output by photomultiplier tube 3 into a voltage signal, which is then output to the controller. The amplification factor of fixed gain amplifier 5 is fixed and remains unchanged during full-scale calibration and measurement. The controller acquires and processes the voltage signal output by fixed gain amplifier 5.

[0042] In this invention, full-scale calibration is not achieved by changing the amplification factor of the fixed-gain amplifier 5, but by adjusting the output voltage of the negative high-voltage power supply 4. Changing the output voltage of the negative high-voltage power supply 4 changes the gain of the photomultiplier tube 3, thereby changing the output of the fixed-gain amplifier 5 corresponding to the same optical signal.

[0043] In this embodiment, the reference light source 6 is a blue light-emitting diode. The emission center wavelength of the blue light-emitting diode matches the emission center wavelength of the chemiluminescence reaction in the light-emitting dish 2, which is 410 nm, so that the spectral response of the reference light on the photosensitive surface corresponds to the spectral response of the chemiluminescence in the light-emitting dish 2 on the photosensitive surface.

[0044] The reference light emitted by the reference light source 6 is guided to the photosensitive surface of the photomultiplier tube 3 via an optical fiber, and the reference light is thus coupled to the photosensitive surface. The luminous intensity of the reference light source 6 is controlled by a controller. In this embodiment, the controller outputs a constant driving current to the blue light-emitting diode via a digital-to-analog converter circuit. Changing the driving current changes the luminous intensity of the reference light.

[0045] When the controller illuminates the reference light source 6, the light-emitting dish 2 is in a state where no chemiluminescence is produced, and the photosensitive surface of the photomultiplier tube 3 only receives the reference light. Accordingly, the reference light becomes a light signal with controllable and reproducible light intensity, which is used as a reference for full-scale calibration.

[0046] Full-scale calibration is completed according to the following steps: The controller controls the addition of a standard solution to the luminescent dish 2 and controls the dosing mechanism to add reagents to the luminescent dish 2, triggering chemiluminescence; the controller sets the output voltage of the negative high voltage power supply 4 to V1, collects the emission peak value of the fixed gain amplifier 5 during the chemiluminescence process, and obtains the output U1 of the fixed gain amplifier 5 corresponding to the chemiluminescence peak value.

[0047] After the chemiluminescence in the luminescent dish 2 ends and the dish 2 is in a state where no chemiluminescence is produced, the controller illuminates the reference light source 6 and adjusts the luminous intensity of the blue light-emitting diode so that the output of the fixed gain amplifier 5 is equal to U1. At this time, the reference light generated by the reference light source 6 and the chemiluminescence induced by the standard solution have the same output at the output terminal of the fixed gain amplifier 5, that is, a reference light with the same intensity as the luminescence of the standard solution is obtained.

[0048] The controller keeps the light intensity of the reference light source 6 constant and increases the output voltage of the negative high voltage power supply 4 from V1 to V2, so that the output of the fixed gain amplifier 5 increases from U1 to the full-scale target value.

[0049] The controller sets V2 to the operating output voltage of the negative high-voltage power supply 4, and then turns off the reference light source 6. After full-scale calibration, the device measures the water sample under test with the negative high-voltage power supply 4 outputting V2.

[0050] In this embodiment, the full-scale target value is 90% of the full-scale value of the measurement range of the fixed gain amplifier 5. The full-scale value of the measurement range of the fixed gain amplifier 5 is the upper limit of the range corresponding to the output voltage of the fixed gain amplifier 5. The measurement is performed when the output of the fixed gain amplifier 5 is 90% of the full-scale value of the measurement range, so that the measurement output is within the linear range of the fixed gain amplifier 5 and the negative high voltage power supply 4 with a margin, and the emission peak value is avoided from exceeding the range.

[0051] In this embodiment, the reference light source 6 is a blue light-emitting diode (LED). The reference light emitted by the LED is adjusted to the same intensity as the chemiluminescence induced by the standard solution, serving as the equivalent light source for the standard solution's luminescence. Thereafter, the chemiluminescence of the standard solution is not repeatedly induced. Instead, based on this equivalent light source, the output voltage of the negative high-voltage power supply 4 is adjusted to align the output of the fixed-gain amplifier 5 to the full-scale target value, forming a closed-loop adjustment with the output of the fixed-gain amplifier 5 as feedback. This full-scale calibration method is called the blue LED equivalent light source closed-loop calibration. After the blue LED equivalent light source closed-loop calibration, the outputs of each measurement channel at the luminescence intensity corresponding to the standard solution are unified to the same full-scale target value. The gain differences of the photomultiplier tube 3 between different measurement channels and over time are compensated by the output voltage of the negative high-voltage power supply 4.

[0052] After the above calibration, the output of each measurement channel at the corresponding luminescence intensity of the standard solution is unified to the same full-scale target value. The gain differences of photomultiplier tube 3 between different measurement channels and with the time of use are compensated by the output voltage of negative high-voltage power supply 4. The entire calibration only requires one chemiluminescence of the standard solution. Subsequent full-scale adjustments are completed based on the reference light when the luminescence dish 2 does not produce chemiluminescence, without repeatedly inducing chemiluminescence of the standard solution.

[0053] If the emission peak reaches the full-scale value of the fixed gain amplifier 5 during the measurement process, the controller reduces the output voltage of the negative high voltage power supply 4 and recalibrates the full scale to bring the measurement output within the range.

[0054] In this embodiment, the photomultiplier tube 3 is sensitive to magnetic fields. When magnetic fields in the environment, including the Earth's magnetic field, act on the photomultiplier tube 3, they will change the trajectory of electrons inside it, causing a change in the gain of the photomultiplier tube 3. To suppress the influence of magnetic fields on the photomultiplier tube 3, the photomultiplier tube 3 is equipped with an inner antimagnetic shield 7 and an outer antimagnetic shield 8.

[0055] The inner antimagnetic shield 7 is fitted around the photomultiplier tube 3, and the outer antimagnetic shield 8 is fitted around the inner antimagnetic shield 7, with a gap between the inner antimagnetic shield 7 and the outer antimagnetic shield 8. Both the inner antimagnetic shield 7 and the outer antimagnetic shield 8 are made of soft magnetic low-carbon steel.

[0056] The inner magnetic shield 7 is circular, and its shape is adapted to the shape of the photomultiplier tube 3, so that the inner magnetic shield 7 fits snugly on the outside of the photomultiplier tube 3; the outer magnetic shield 8 is square, which facilitates the assembly and positioning of the outer magnetic shield 8 with the chassis 1.

[0057] The inner magnetic shield 7 and the outer magnetic shield 8 are made of soft magnetic low-carbon steel. The high permeability of soft magnetic low-carbon steel provides a low magnetic resistance path for the magnetic field, allowing the external magnetic field to pass through the two layers of soft magnetic low-carbon steel, thereby reducing the magnetic field strength reaching the photomultiplier tube 3. The inner magnetic shield 7 and the outer magnetic shield 8 are arranged sequentially to form a two-stage shield for the magnetic field.

[0058] The inner magnetic shield 7 is electrically connected to the shielding wire of the photocurrent output, and the outer magnetic shield 8 is electrically connected to the chassis 1. The inner magnetic shield 7 is close to the photomultiplier tube 3 and is electrically connected to the shielding wire of the photocurrent output, forming an electrical shield for the weak photocurrent signal output by the photomultiplier tube 3; the outer magnetic shield 8 is electrically connected to the chassis 1, forming an outer layer of electrical shield.

[0059] Therefore, the inner antimagnetic shield 7 and the outer antimagnetic shield 8 are made of soft magnetic low carbon steel to shield the magnetic field, and are also electrically connected to the shielding wire of the photocurrent output and the chassis 1 to shield the electric field. The magnetic shielding and the electric shielding are achieved by the same shielding structure.

[0060] A reference light source 6 is positioned within the gap between the inner magnetic shield 7 and the outer magnetic shield 8. The reference light emitted by the reference light source 6 is guided through an optical fiber via the inner magnetic shield 7 to the photosensitive surface of the photomultiplier tube 3. The reference light source 6, positioned within the gap between the inner and outer magnetic shields, provides reference light to the photosensitive surface without disrupting the secure fit of the inner magnetic shield 7 to the photomultiplier tube 3, nor altering the shielding of the inner and outer magnetic shields 7 and 8 against magnetic and electric fields.

[0061] The gap between the inner antimagnetic shield 7 and the outer antimagnetic shield 8 is also filled with insulating filler. The insulating filler is used to dampen the photomultiplier tube 3, keep it warm, and insulate the inner antimagnetic shield 7 from the outer antimagnetic shield 8.

[0062] In this embodiment, the dosing mechanism includes a negative pressure air pump 9, a positive pressure air pump 10, a metering pipeline 11, and a liquid level sensor 12 installed on the metering pipeline 11. The dosing mechanism is used to quantitatively add three reagents—oxidant, reducing agent, and luminescent agent—to the luminescent dish 2.

[0063] One end of the metering line 11 is connected to the reagent bottle, and the other end is connected to the luminescent dish 2. A liquid level sensor 12 is installed on the metering line 11 to detect whether the liquid level in the metering line 11 has reached its designated position, and outputs the detection result to the controller. A negative pressure air pump 9 is connected to the metering line 11 to create a negative pressure within the metering line 11; a positive pressure air pump 10 is connected to the metering line 11 to create a positive pressure within the metering line 11.

[0064] The metering line 11 is also equipped with an electromagnetic three-way valve and a check valve. The oxidant, reducing agent, and luminescent agent share a negative pressure air pump 9 and a positive pressure air pump 10. Each reagent's corresponding line is connected to the metering line 11 via its own electromagnetic three-way valve. The negative pressure air pump 9 and the positive pressure air pump 10 are connected to the metering line 11 via the electromagnetic three-way valve. The check valve, located in the metering line 11, limits the flow direction of the reagents and gas within the line, ensuring that the reagents flow unidirectionally from the reagent bottle through the metering line 11 to the luminescent dish 2. It also prevents cross-flow between different reagents and between the reagents and the gas path, and prevents backflow of liquid from the luminescent dish 2 into the metering line 11.

[0065] The dosing mechanism completes one dosing operation for each reagent in the sequence of extraction, metering, and dosing, using a two-stage gravity reflux metering method. The process is as follows: The controller controls the negative pressure air pump 9 to operate, creating a negative pressure in the metering line 11. The reagent in the reagent bottle is drawn into the metering line 11, causing the liquid level in the metering line 11 to rise. When the liquid level in the metering line 11 reaches the position of the liquid level sensor 12, the controller controls the negative pressure air pump 9 to stop.

[0066] When the negative pressure air pump 9 stops, its motor continues to rotate due to inertia, and the negative pressure in the metering pipeline 11 continues to rise, causing the liquid level in the metering pipeline 11 to exceed the position of the liquid level sensor 12.

[0067] After the negative pressure air pump 9 stops, the controller reduces the negative pressure in the metering pipeline 11 by depressurizing, causing the liquid level in the metering pipeline 11 that has passed the location of the liquid level sensor 12 to fall back under the influence of gravity. In this embodiment, the dosing mechanism is equipped with a hollow screw for depressurization. By adjusting the opening of the hollow screw, the metering pipeline 11 is slowly depressurized, and the liquid level that has passed the location of the liquid level sensor 12 slowly falls back.

[0068] When the receding liquid level passes the position of the level sensor 12 again, the controller determines that the reagent metering is complete. The volume of reagent below the position of the level sensor 12 in the metering pipeline 11 is the metered volume of one dosing.

[0069] In this embodiment, reagent metering is based on the liquid level in the metering pipeline 11 passing the position of the liquid level sensor 12 for the second time. When the negative pressure air pump 9 stops, the liquid level exceeding the position of the liquid level sensor 12 due to the motor inertia is eliminated after depressurization. The repeatability error of reagent metering of the dosing mechanism is within two per thousand.

[0070] After the metering is completed, the controller activates the positive pressure pump 10, which creates positive pressure in the metering line 11, allowing the metered reagent to be added to the luminescent dish 2. After the addition is complete, the positive pressure pump 10 continues to supply air to the metering line 11 to purge it and remove any remaining reagent, preparing for the next reagent extraction and metering.

[0071] The electromagnetic three-way valves corresponding to the oxidant, reducing agent and luminescent agent are connected to the metering pipeline 11 in a time-sharing manner. The controller controls the three reagents in sequence to complete their respective extraction, metering and dosing. The three reagents share the negative pressure air pump 9 and the positive pressure air pump 10 to complete the quantitative addition.

[0072] In this embodiment, the luminescent dish 2 is disposed inside the housing 1 and is used to hold the water sample to be tested and receive the reagents added by the dosing mechanism. Its volume is 12mL to 18mL. The top of the luminescent dish 2 is provided with a reagent inlet for the dosing mechanism to add oxidant, reducing agent and luminescent agent. The side wall of the luminescent dish 2 faces the photosensitive surface of the photomultiplier tube 3, forming the photometric position of the luminescent dish 2.

[0073] The volume of the luminescent dish 2 is 12mL-18mL. After the reagent is added to the luminescent dish 2, it mixes with the water sample to be tested contained in the luminescent dish 2 in a large liquid volume and triggers chemiluminescence. The photomultiplier tube 3 receives the chemiluminescence at the photometric position.

[0074] The luminescent dish 2 is connected to a water inlet pipe and a water outlet pipe. The water inlet pipe is used to fill the luminescent dish 2 with the water sample to be tested, and the water outlet pipe is used to drain the liquid from the luminescent dish 2.

[0075] The luminescent dish 2 is equipped with a siphon tube 13. The inlet of the siphon tube 13 is located inside the luminescent dish 2, and the height of its opening corresponds to the set volume of the water sample to be tested inside the luminescent dish 2. When the water sample fills the luminescent dish 2, the water sample height rises to the highest point of the siphon tube 13, forming a siphon effect that discharges the water sample in the luminescent dish 2 that is higher than the set volume. When the water sample height in the luminescent dish 2 drops to the inlet of the siphon tube 13, the siphon stops, and the water sample remaining in the luminescent dish 2 is the set volume.

[0076] A water flow sensor 14 is installed on the body of the siphon tube 13. The water flow sensor 14 is electrically connected to the controller and is used to detect the water flow in the siphon tube 13 and output a signal to the controller.

[0077] In this embodiment, the water flow sensor 14 is disposed on the body of the siphon tube 13, rather than on the water inlet pipe. During the process of filling the light-emitting dish 2 with the water sample to be tested, the water inlet pipe often draws in air, and this air-liquid mixture can cause false alarms from the sensor disposed on the water inlet pipe. Water only flows through the siphon tube 13 when the light-emitting dish 2 is full and a siphon is formed; using the water flow within the siphon tube 13 as a criterion provides a clear and reliable signal.

[0078] Based on the water flow detection in the siphon tube 13 by the water flow sensor 14, the controller controls the luminescent dish 2 to sequentially complete the soaking, rinsing, and quantitative retention of the water sample to be tested. The process is as follows: The controller controls the water sample to be tested to be filled into the luminescent dish 2 through the inlet pipe. When the water flow sensor 14 detects the water flow in the siphon tube 13 for the first time, it indicates that the luminescent dish 2 is full and begins to siphon. At this time, the water sample to be tested has soaked and rinsed the luminescent dish 2 and the pipe. Then the controller controls the luminescent dish 2 to be emptied through the drain pipe.

[0079] Subsequently, the controller again controls the water sample to be tested to be filled into the luminescent dish 2 through the water inlet pipe. The water flow sensor 14 detects the water flow in the siphon tube 13 for the second time. The water sample to be tested filled in this time causes the water sample height in the luminescent dish 2 to rise above the height of the siphon tube 13 opening. The siphon tube 13 forms a siphon again and discharges the water sample to be tested that is higher than the set volume. When the water sample height in the luminescent dish 2 drops to the inlet of the siphon tube 13 and the water flow in the siphon tube 13 changes from being detected by the water flow sensor 14 to being undetectable, it indicates that this siphoning is over. The luminescent dish 2 retains the set volume of water sample to be tested, and the water sample collection is completed.

[0080] In this invention, the luminescent dish 2 is first soaked and rinsed by the water sample to be tested and drained through the drain pipe before measurement. Then, the water sample to be tested is filled in and quantitatively retained by the siphon tube 13, so that the water sample remaining in the luminescent dish 2 and the water inlet pipe from the previous measurement is replaced by the water sample to be tested in this measurement. This reduces cross-contamination between the previous and subsequent measurements and is suitable for measuring water samples with extremely low iron content.

[0081] The quantitative determination of the water sample to be tested in the luminescent dish 2 is accomplished by the siphon tube 13. The siphon tube 13 discharges a water sample higher than the set volume according to the siphon principle. The volume of the water sample to be tested in the luminescent dish 2 is determined by the height of the siphon tube 13 opening, and the drainage volume is not controlled by the valve on the drainage pipeline.

[0082] In this embodiment, the reagents added to the luminescent dish 2 by the dosing mechanism include three types: oxidant, reducing agent, and luminescent agent. The three reagents are stored in their respective reagent bottles and added to the luminescent dish 2 in measured quantities by the dosing mechanism.

[0083] The oxidant is a solution containing potassium periodate or potassium iodate. Potassium periodate has the chemical formula KIO4, and potassium iodate has the chemical formula KIO3; both are used to oxidize luminol in the chemiluminescence reaction. In this embodiment, the oxidant also contains a sensitizer to enhance the intensity of chemiluminescence within the luminescent dish 2. In this embodiment, the amount of oxidant added at one time is 0.5 mL.

[0084] The reducing agent is a solution containing sodium bisulfite, with the chemical formula NaHSO3. Sodium bisulfite is used to reduce ferric ions in the water sample to ferrous ions, allowing the iron in the water sample to participate in chemiluminescence as ferrous ions. In this embodiment, the amount of reducing agent added at one time is 0.5 mL.

[0085] The luminescent agent is an alkaline solution of luminol. Luminol in the luminescent agent is the main luminescent component for chemiluminescence. The luminescent agent is alkaline so that luminol is oxidized by the oxidant under alkaline conditions and emits light. In this embodiment, the luminescent agent also contains a stabilizer to maintain its stability. In this embodiment, the amount of luminescent agent added at one time is 2.0 mL.

[0086] In this invention, the oxidant is a solution containing potassium periodate or potassium iodate. Potassium permanganate solution has poor stability and is purplish-red, interfering with the chemiluminescence light signal; potassium ferrate itself contains iron, and when used as an oxidant, it introduces iron ions into the water sample, affecting the measurement of iron content in the water sample. Using potassium periodate or potassium iodate as the oxidant avoids the aforementioned interference.

[0087] In this invention, the reducing agent is a solution containing sodium bisulfite. Sodium bisulfite reduces ferric ions in the water sample to ferrous ions without introducing ferric ions into the water sample, and its reduction product does not interfere with the chemiluminescence in the luminescent dish 2.

[0088] The dosing mechanism adds three reagents to the luminescent dish 2 in the following order. The controller first controls the dosing mechanism to add a reducing agent into the luminescent dish 2, which is added from the bottom of the dish 2. Then, the controller controls the air to be introduced into the luminescent dish 2 to stir the reducing agent and the water sample to be tested in the dish 2, so that they are mixed evenly. The air is introduced for 3 to 5 seconds. After stirring, the mixture is allowed to stand for 15 to 25 seconds to allow the ferric ions in the water sample to be reduced to ferrous ions by the reducing agent.

[0089] After the reduction is completed, the controller controls the dosing mechanism to add oxidant to the luminescent dish 2 and waits for 3 to 5 seconds; then the controller controls the dosing mechanism to add luminescent agent to the luminescent dish 2. After the luminescent agent is added, chemiluminescence is instantly triggered in the luminescent dish 2. The photomultiplier tube 3 collects the luminescence peak value of the chemiluminescence within 3 to 5 seconds after the luminescent agent is added.

[0090] In this embodiment, the air introduced into the luminescent dish 2 is provided by a positive pressure air pump 10. The air generated by the positive pressure air pump 10 is introduced into the luminescent dish 2 through a pipeline, forming an airflow within the dish 2. This airflow stirs the liquid within the dish 2, ensuring that the added reagent and the water sample to be tested are mixed uniformly. When measuring the soluble ferrous iron content in the water sample, no reducing agent is added, eliminating the need for adding a reducing agent, introducing air for stirring, and allowing the sample to settle. Only an oxidizing agent and a luminescent agent are added to initiate chemiluminescence.

[0091] The three reagents, oxidant, reducing agent and luminescent agent, have an inhibitory effect on the interference of copper ions. When the water sample to be tested contains copper ions, the measurement results of iron content by the device are within the set range affected by copper ions.

[0092] In this embodiment, the device measures the soluble ferrous iron (Fe2+) content and the soluble total iron content of the same water sample, and obtains the soluble ferric iron (Fe3+) content accordingly. Since ferrous ions play a role in enhancing chemiluminescence in the luminescent dish 2, the addition of a reducing agent determines the iron ions participating in luminescence in the water sample.

[0093] When the device measures the first water sample, the controller controls the dosing mechanism to add only oxidant and luminescent agent without adding a reducing agent, thus triggering chemiluminescence. At this time, only the ferrous ions originally present in the first water sample participate in luminescence. The controller collects the luminescence peak value output by the fixed gain amplifier 5 to obtain the first luminescence amount, which corresponds to the soluble ferrous iron content in the first water sample.

[0094] When the device measures the second water sample, the controller controls the dosing mechanism to add a reducing agent, an oxidizing agent, and a luminescent agent, triggering chemiluminescence. The reducing agent reduces the ferric ions in the second water sample to ferrous ions. The original ferrous ions in the second water sample, along with the ferrous ions obtained from the reduction of ferric ions, participate in the luminescence. The controller collects the peak value of the luminescence output from the fixed-gain amplifier 5 to obtain the second luminescence amount, which corresponds to the total soluble iron content of the second water sample.

[0095] The controller determines the soluble ferrous iron content based on the first emission level and the soluble total iron content based on the second emission level. The correspondence between emission level and iron content is determined in advance by the device using a standard solution with known concentrations. Based on this, the controller converts the first emission level into soluble ferrous iron content and the second emission level into soluble total iron content.

[0096] The controller uses the difference between the total soluble iron content and the soluble ferrous iron content to determine the soluble ferric iron content of the second water sample. Thus, the device measures both the soluble ferrous iron content and the total soluble iron content separately, and obtains the soluble ferric iron content.

[0097] In this embodiment, no reducing agent is added when measuring the soluble ferrous iron content, eliminating the need for adding the reducing agent, agitating with air, and allowing time for settling. Therefore, the time required to measure the soluble ferrous iron content is shorter than that required to measure the soluble total iron content. The detection limit for iron content is 0.01 μg / L, and the relative deviation of the measurement results is no greater than 1 microgram. The time required to measure the soluble total iron content of one water sample is 70 seconds, and the time required to measure the soluble ferrous iron content of one water sample is 45 seconds.

[0098] In this embodiment, the device is a desktop unit housed within a chassis 1, used for offline measurement of the water sample obtained from sampling. The chassis 1 contains a luminescent dish 2, a photomultiplier tube 3, a negative high-voltage power supply 4, a fixed-gain amplifier 5, a reference light source 6, an inner anti-magnetic shield 7, an outer anti-magnetic shield 8, a dosing mechanism, and a controller. Externally connected to the chassis 1 are reagent bottles containing oxidant, reducing agent, and luminescent agent, as well as the water sample to be tested.

[0099] After the device is powered on, the controller controls the device to perform a self-test, and then controls the addition of a standard solution and reagents to the luminescent dish 2 to trigger chemiluminescence. Following the aforementioned full-scale calibration steps, the output voltage of the negative high-voltage power supply 4 is determined as the working output voltage V2.

[0100] The procedure for a single measurement of the soluble total iron content in the water sample is as follows: The controller controls the water sample to be tested to be filled into the luminescent dish 2 through the water inlet pipe. The water flow sensor 14 detects the water flow in the siphon tube 13 for the first time, indicating that the luminescent dish 2 is full and begins to siphon. The water sample to be tested soaks and rinses the luminescent dish 2. Then the controller controls the luminescent dish 2 to be emptied through the drain pipe. The controller controls the water sample to be tested to be filled into the light-emitting dish 2 again through the water inlet pipe. The water flow sensor 14 detects the water flow in the siphon tube 13 for the second time. The siphon tube 13 discharges the water sample to be tested at a volume higher than the set volume. When the water flow in the siphon tube 13 changes from being detected by the water flow sensor 14 to being undetectable, the siphon ends and the light-emitting dish 2 retains the set volume of the water sample to be tested. The controller controls the dosing mechanism to add a reducing agent to the luminescent dish 2, and introduces air into the luminescent dish 2 to stir the reducing agent and the water sample to be tested. After standing, the ferric ions in the water sample to be tested are reduced to ferrous ions. Then, an oxidizing agent is added to the luminescent dish 2, and finally, a luminescent agent is added to the luminescent dish 2. The water sample to be tested and the reagent are mixed in the luminescent dish 2 and chemiluminescence is initiated. The photomultiplier tube 3 receives the chemiluminescence in the light-emitting dish 2 and outputs a photocurrent. After being amplified by the fixed gain amplifier 5, the photocurrent is output to the controller. The controller collects the peak value of the chemiluminescence to obtain the amount of light emitted. The controller obtains the total soluble iron content of the water sample to be tested based on the amount of light emitted. After the measurement is completed, the controller controls the light-emitting dish 2 to be emptied through the drainage pipe and purges the light-emitting dish 2 and the metering pipe 11 to reset the device and prepare for the next measurement.

[0101] In this embodiment, the volume of the luminescent dish 2 of the device is 12mL to 18mL. The reagent is directly added to the water sample to be tested in the luminescent dish 2 for mixing and light measurement. The liquid phase volume in the luminescent dish 2 is relatively large, and the detection limit of the device for iron content is 0.01μg / L.

[0102] In this embodiment, the time required for the device to measure the total soluble iron content of a water sample is 70 seconds; when only oxidant and luminescent agent are added and no reducing agent is added to measure the soluble ferrous iron content, the time required is 45 seconds; the reagent cost consumed by the device to measure a water sample is 0.1 yuan.

[0103] In this invention, the device provides repeatable measurements of iron content. Table 1 shows the results of measuring the total soluble iron content of the same water sample using four different devices.

[0104]

[0105] Table 1 In this invention, when the device measures the iron content of a water sample containing copper ions, the influence of copper ions on the measurement results is suppressed. Table 2 shows the recovery rates of the iron content measurement results after adding different amounts of copper ions to the water sample.

[0106]

[0107] Table 2 As shown in Table 1, the measured values ​​of soluble total iron content of the same water sample by the four devices are close to each other; as shown in Table 2, when the amount of copper ions added to the water sample is 0 μg / L to 20 μg / L, the recovery rate of iron content measurement by the device is 97.0% to 100.4%.

[0108] In this embodiment, the device, based on the offline benchtop device of Embodiment 1, also includes a multi-way sampling valve, an overflow tank, and an alarm unit, forming an online iron ion analyzer for continuous online measurement of the water sample to be tested.

[0109] The multi-port sampling valve has multiple inlets and one outlet. Each inlet is connected to the sampling pipeline of the water sample to be tested, the standard solution, and the cleaning water, respectively. The outlet is connected to the water inlet pipeline of the luminescent dish 2. The multi-port sampling valve is electrically connected to a controller, which controls the switching of the multi-port sampling valve so that the water sample to be tested, the standard solution, or the cleaning water can be selected to enter the luminescent dish 2 through the water inlet pipeline.

[0110] When the controller switches the water sample to be tested into the luminescent dish 2 via the multi-channel injection valve, the device measures the water sample; when the standard solution is switched into the luminescent dish 2, the device performs full-scale calibration; when the cleaning water is switched into the luminescent dish 2, the device cleans the luminescent dish 2 and the pipeline.

[0111] The overflow tank is connected to the sampling pipeline of the water sample to be tested. The water sample introduced into the sampling pipeline first enters the overflow tank, and the overflow tank provides the water sample to the multi-way sampling valve. The water sample in the overflow tank that is higher than its overflow port is discharged through the overflow port. The overflow tank keeps the pressure of the water sample entering the device stable.

[0112] The alarm unit is electrically connected to the controller and is used to issue an alarm when the device's operating status is abnormal. In this embodiment, the alarm unit includes a water shortage alarm, an over-temperature alarm, and a water quality deterioration alarm.

[0113] The controller issues an alarm via water outage alarm when the water sample in the sampling pipeline is interrupted; an alarm via over-temperature alarm when the temperature inside the device exceeds the set value; and an alarm via water quality deterioration alarm when the measurement results of the water sample indicate that the water quality has deteriorated.

[0114] During operation, the online iron ion analyzer uses a controller to switch multiple injection valves according to a set cycle to continuously measure the water sample to be tested. It also switches standard solutions for full-scale calibration according to a set cycle, switches to cleaning water for cleaning, and outputs the measured soluble iron content.

[0115] In this embodiment, in addition to the reagent inlets for adding oxidizing agents, reducing agents, and luminescent agents, the luminescent dish 2 also has one or two additional reagent inlets for adding reagents required for the determination of other ions. The dosing mechanism adds the corresponding reagents to the luminescent dish 2 through the additional reagent inlets, enabling the device to measure the content of other ions in the water sample in addition to the iron content.

[0116] In this embodiment, in addition to using blue light-emitting diodes, the reference light source 6 also uses other light-emitting elements whose emission center wavelength matches the emission center wavelength of the chemiluminescence reaction in the light-emitting dish 2; in addition to using two layers, the inner antimagnetic shield 7 and the outer antimagnetic shield 8 are also equipped with additional shields according to the requirements for magnetic field shielding.

[0117] The device of this invention integrates a light-emitting dish 2, a photomultiplier tube 3, a negative high-voltage power supply 4, a fixed-gain amplifier 5, a dosing mechanism, a reference light source 6, and a controller into a housing 1. After reagents are connected, the controller automatically completes dosing, chemiluminescence, signal acquisition, full-scale calibration, and content calculation, without requiring acid boiling of the water sample to be tested. The fixed-gain amplifier 5 has a fixed amplification factor, and the full-scale calibration is handled by the output voltage of the negative high-voltage power supply 4 and is completed based on the reference light generated by the reference light source 6, ensuring uniform full-scale values ​​for each measurement channel. The inner anti-magnetic shield 7 and the outer anti-magnetic shield 8 protect the photoelectric... The multiplier tube 3 simultaneously forms magnetic and electrical shielding; the dosing mechanism uses the inertia of the motor to cause the liquid level to pass over the liquid level sensor 12, and after depressurization and return, the liquid level passes over the liquid level sensor 12 a second time to determine that the metering is in place, thus improving the repeatability of reagent metering; the water flow sensor 14 is set on the siphon tube 13 to avoid false alarms caused by air being sucked into the water inlet pipe; the luminescent dish 2 is quantitatively retained by the siphon tube 13 after being soaked and rinsed by the water sample to be tested, thus reducing cross-contamination between the previous and subsequent measurements; the device measures the soluble ferrous iron content and the soluble total iron content separately, and obtains the soluble ferric iron content.

[0118] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A device for rapidly detecting trace iron ion content in water, comprising a housing (1), a light-emitting dish (2) disposed within the housing (1), a photomultiplier tube (3) disposed at the photometric position of the light-emitting dish (2), a negative high-voltage power supply (4) for supplying power to the photomultiplier tube (3), a dosing mechanism, and a controller, wherein the light-emitting dish (2) is used to contain the water sample to be tested and to receive the reagent added by the dosing mechanism, the water sample to be tested and the reagent are mixed in the light-emitting dish (2) and trigger chemiluminescence, and the photomultiplier tube (3) is used to receive the chemiluminescence in the light-emitting dish (2), characterized in that, The chassis (1) is also equipped with a fixed gain amplifier (5) and a reference light source (6). The output end of the photomultiplier tube (3) is electrically connected to the controller via the fixed gain amplifier (5). The reference light source (6) is electrically connected to the controller, and the luminous intensity of the reference light source (6) is controlled by the controller. The reference light source (6) emits reference light and couples it to the photosensitive surface of the photomultiplier tube (3). The controller is electrically connected to the negative high voltage power supply (4). When the light-emitting dish (2) does not produce chemiluminescence, the controller lights up the reference light source (6) and adjusts the output voltage of the negative high voltage power supply (4) so ​​that the output of the fixed gain amplifier (5) is aligned to the preset full-scale target value to complete the full-scale calibration.

2. The device for rapid detection of trace iron ion content in water according to claim 1, characterized in that, The photomultiplier tube (3) is covered with an inner antimagnetic shield (7), and the inner antimagnetic shield (7) is covered with an outer antimagnetic shield (8). There is a gap between the inner antimagnetic shield (7) and the outer antimagnetic shield (8). The reference light source (6) is placed in the gap. The reference light emitted by the reference light source (6) passes through the inner antimagnetic shield (7) via an optical fiber and is coupled to the photosensitive surface of the photomultiplier tube (3).

3. The device for rapid detection of trace iron ion content in water according to claim 2, characterized in that, The inner antimagnetic shield (7) and the outer antimagnetic shield (8) are both made of soft magnetic low carbon steel. The inner antimagnetic shield (7) is circular and the outer antimagnetic shield (8) is square. The inner antimagnetic shield (7) is electrically connected to the shielding line of the photocurrent output and the outer antimagnetic shield (8) is electrically connected to the chassis (1).

4. The device for rapid detection of trace iron ion content in water according to claim 1, characterized in that, The reference light source (6) is a blue light-emitting diode, and the emission center wavelength of the blue light-emitting diode matches the emission center wavelength of the chemiluminescence reaction in the light-emitting dish (2).

5. The device for rapid detection of trace iron ion content in water according to claim 1, characterized in that, The full-scale target value is 90% of the full-scale value of the measurement range of the fixed gain amplifier (5).

6. The device for rapid detection of trace iron ion content in water according to claim 1, characterized in that, The full-scale calibration step includes: The standard solution is added to the luminescent dish (2) by the controller and the reagent is added to the luminescent dish (2) by the dosing mechanism to induce chemiluminescence. When the output voltage of the negative high voltage power supply (4) is V1, the output U1 of the fixed gain amplifier (5) corresponding to the peak value of chemiluminescence is measured. Adjust the luminescence intensity of the reference light source (6) so that the output of the fixed gain amplifier (5) is equal to U1 when the luminescent dish (2) does not produce chemiluminescence. Keeping the luminous intensity of the reference light source (6) constant, the output voltage of the negative high voltage power supply (4) is increased from V1 to V2, so that the output of the fixed gain amplifier (5) is increased from U1 to the full-scale target value; V2 is determined as the working output voltage of the negative high voltage power supply (4).

7. The device for rapid detection of trace iron ion content in water according to claim 1, characterized in that, The dosing mechanism includes a negative pressure air pump (9), a positive pressure air pump (10), a metering pipeline (11), and a liquid level sensor (12) installed on the metering pipeline. One end of the metering pipeline (11) is connected to the reagent bottle, and the other end is connected to the luminescent dish (2). The negative pressure air pump (9) is connected to the metering pipeline (11) and is used to create a negative pressure inside the metering pipeline (11). The positive pressure air pump (10) is connected to the metering pipeline (11) and is used to create a positive pressure inside the metering pipeline (11). The liquid level sensor (12) is connected to the controller. The connection is made so that the negative pressure air pump (9) controlled by the controller lifts the reagent in the reagent bottle into the metering pipeline (11), causing the liquid level in the metering pipeline (11) to rise. When the liquid level reaches the liquid level sensor (12), the negative pressure air pump (9) is controlled to stop. After the negative pressure air pump (9) stops, the liquid level that has passed the liquid level sensor (12) is depressurized and falls back. When the liquid level passes the liquid level sensor (12) again, it is determined that the reagent is metered in place. After the metering is in place, the positive pressure air pump (10) is controlled to add the reagent in the metering pipeline (11) into the luminescent dish (2).

8. The device for rapid detection of trace iron ion content in water according to claim 1, characterized in that, The volume of the luminescent dish (2) is 12mL-18mL. The luminescent dish (2) is connected to an inlet pipe and an outlet pipe. A siphon tube (13) is provided on the luminescent dish (2). The inlet of the siphon tube (13) is located inside the luminescent dish (2), and the height of its opening corresponds to the set volume of the water sample to be tested in the luminescent dish (2). The siphon tube (13) is used to discharge the water sample to be tested that is higher than the set volume in the luminescent dish (2). A water flow sensor (14) is provided on the tube body of the siphon tube (13). The water flow sensor (14) is electrically connected to the controller. It is used to detect the water flow in the siphon tube (13). The controller controls the water sample to be tested to be filled into the light-emitting dish (2) through the water inlet pipe. When the water flow sensor (14) detects the water flow in the siphon tube (13) for the first time, the controller controls the light-emitting dish (2) to be emptied through the drain pipe to soak and rinse the light-emitting dish (2). Then, the controller controls the water sample to be tested to be filled into the light-emitting dish (2) through the water inlet pipe. When the water flow sensor (14) detects the water flow in the siphon tube (13) for the second time and the water flow changes from being detected to being undetectable, it is determined that a set volume of water sample to be tested is retained in the light-emitting dish (2).

9. The device for rapid detection of trace iron ion content in water according to claim 1, characterized in that, The reagents include an oxidizing agent, a reducing agent, and a luminescent agent. The oxidizing agent is a solution containing potassium periodate or a solution containing potassium iodate. The reducing agent is a solution containing sodium bisulfite. The luminescent agent is an alkaline solution of luminol. The controller controls the dosing mechanism to add reagents to the luminescent dish (2) in the following order: First, add a reducing agent to the luminescent dish (2) and then introduce air into the luminescent dish (2) to stir the reducing agent and the water sample to be tested. After standing, reduce the ferric ions in the water sample to ferrous ions. Then add an oxidizing agent to the luminescent dish (2) and finally add a luminescent agent to the luminescent dish (2) to initiate chemiluminescence.

10. The device for rapid detection of trace iron ion content in water according to claim 9, characterized in that, The controller controls the dosing mechanism to add only oxidant and luminescent agent to the first water sample to be tested to induce chemiluminescence, thereby obtaining a first luminescence amount corresponding to the soluble ferrous iron content. The controller also controls the dosing mechanism to add reducing agent, oxidant and luminescent agent to the second water sample to be tested to induce chemiluminescence, thereby obtaining a second luminescence amount corresponding to the soluble total iron content. The soluble ferric iron content is obtained by the difference between the soluble total iron content and the soluble ferrous iron content.

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