A method and apparatus for detecting impurity elements in organic solutions

Abstract

This invention discloses a method and apparatus for detecting impurity elements in organic solutions, belonging to the field of component detection technology. The apparatus includes an ICP system, a sample introduction system, and a spectroscopic analysis unit. The ICP system has a three-layer concentric rectangular tube structure, with an enlarged inner diameter and a narrowed opening in the central tube, and the inner wall coated with yttrium oxide. The outer and middle tubes form independent cooling and auxiliary gas channels. The sample introduction system includes a temperature-controlled nebulizer chamber and a three-way mixing valve. The spectroscopic analysis unit uses a two-point background correction method to process the signal. The method uses a 1.6-1.8 kW gradient power to excite and create an online micro-oxidation environment, acquires the signal, performs two-point background correction, and calculates the concentration using a matrix-matched calibration curve. This invention achieves continuous and stable plasma operation with no significant carbon buildup, and the relative standard deviation of continuous measurements is <3%, making it suitable for batch detection of various organic solutions.

Description

Technical Field

[0001] This invention relates to the field of component detection technology, and in particular to a method and apparatus for detecting impurity elements in organic solutions. It is applicable to the accurate detection of trace metal and non-metal impurity elements in various organic solutions such as lubricating oil, kerosene, gasoline, diesel, and ethanol, and can be widely used in quality inspection and process monitoring in industries such as petrochemicals, new energy, and fine chemicals. Background Technology

[0002] ICP-OES (Inductively Coupled Plasma Atomic Emission Spectroscopy) is a plasma-based spectroscopic analysis method widely used for detecting metallic and non-metallic impurities. ICP-OES detection technology introduces a sample into a plasma, exciting it to emit light of specific wavelengths. The intensity of this light is then measured to determine the elemental content. ICP-OES has lower sensitivity for detecting low concentrations of elements, making it more suitable for detecting higher concentrations. It has a wide linear range. However, when determining elemental impurities, it is affected by spectral and non-spectral interferences, especially when the composition of the sample solution differs significantly from that of the standard solution.

[0003] For impurities in organic solutions, such as those found in kerosene, gasoline, diesel, and ethanol, the organic solution is typically atomized and introduced into the plasma torch of an inductively coupled plasma (ICP) device. Within the torch, it is ignited by argon plasma and combusted. The combustion flame of the atomized organic matter is then analyzed using an OES (Optical Sequencing Spectroscopy) spectrometer. Based on the detected spectral signals, qualitative and quantitative analysis is performed using software. This spectral analysis reveals the composition and content of metallic or non-metallic impurities in the organic solution.

[0004] However, existing technologies for detecting organic solutions have several drawbacks: the heat released from the combustion of organic solutions in plasma alters the internal temperature gradient of the plasma, disrupting the stability of the gas flow; carbonaceous compounds produced during incomplete combustion interfere with the plasma excitation state and adhere to the inner wall of the rectangular tube, further exacerbating plasma instability and even causing plasma extinguishing, making it impossible to maintain the detection process; simultaneously, the matrix differences between sample solutions and standard solutions easily induce spectral and non-spectral interferences, reducing detection accuracy; furthermore, high-viscosity organic solutions are difficult to atomize, further affecting the stability and accuracy of detection. Currently, there is no effective solution to address these problems, making it difficult to achieve stable and accurate detection of impurity elements in organic solutions.

[0005] Therefore, how to use ICP-OES technology to perform stable and accurate detection of impurities in organic solutions has become a technical problem that needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a method and apparatus for detecting impurity elements in organic solutions, which solves the problems of poor stability, low accuracy, easy carbon buildup in rectangular tubes, and short lifespan of core components in the existing ICP-OES technology for detecting impurities in organic solutions. It enables accurate and efficient detection of trace elements in complex organic matrices, improves measurement accuracy and stability, extends the lifespan of core components, and simplifies the pretreatment process to adapt to batch sample detection.

[0007] To achieve the above objectives, the present invention provides the following technical solution: According to one aspect of the present invention, an apparatus for detecting impurity elements in an organic solution is provided, comprising an ICP system, a sample introduction system, and a spectroscopic analysis unit. The ICP system includes a rectangular tube, an excitation power supply, and an excitation coil. The excitation coil is arranged around the outside of the top of the rectangular tube. Under the excitation of the excitation power supply, the auxiliary gas is dissociated to generate plasma, forming a high-temperature plasma environment, which ionizes the elements in the sample and emits light. The rectangular tube comprises an outer tube, a middle tube, and a central tube, which are coaxially nested in a three-layer concentric structure. The inner diameter D of the central tube and the inner diameter d of the conventional rectangular tube satisfy a ratio of D / d≥1.5. The inner diameter d of the conventional rectangular tube ranges from 1.5 to 2.0 mm. The central tube has a constriction structure at its opening. The constriction is conical with a taper of 15-30°. The constriction length is 3-5 mm, and the constriction outlet diameter is 1.8-2.2 mm. The inner wall of the constriction smoothly transitions to the inner wall of the central tube.

[0008] According to one embodiment of the present invention, the inner wall of the central tube is coated with an 80-150 micrometer thick yttrium oxide coating, which is prepared by plasma-enhanced chemical vapor deposition and has an adhesion of ≥5 MPa.

[0009] According to one embodiment of the present invention, the ratio D / d between the inner diameter D of the central tube and the inner diameter d of the conventional tube ranges from 1.5 to 2.3.

[0010] According to one embodiment of the present invention, the inner diameter D of the central tube is specifically 2.5-3.5 mm, forming an annular auxiliary air channel with a width of 0.1-0.6 mm with the inner wall of the central tube, and the effective working section length is 12-15 mm.

[0011] According to one embodiment of the present invention, the inner diameter of the middle tube is 4.0-6.0 mm, forming an annular cooling gas channel with a width of 1.0-2.0 mm with the inner wall of the outer tube, and the effective working section length is 15-18 mm; an auxiliary gas interface is provided in the lower middle part of the outer wall of the middle tube, which is connected to the auxiliary gas path of the ICP system; the auxiliary gas flows upward along the annular gap between the inner wall of the middle tube and the outer wall of the central tube, which is used to stabilize the plasma in the middle region of the rectangular tube and to regulate the flame core diameter of the plasma by adjusting the flow rate.

[0012] According to one embodiment of the present invention, the inner diameter of the outer tube is 6.5-10.0 mm, the effective working section length is 18-22 mm, which is adapted to the winding range of the excitation coil of the ICP system, and the overall length is 45-55 mm; the cooling gas interface is provided at the bottom of the outer wall of the outer tube, which is sealed to the cooling gas path of the ICP system; the cooling gas flows upward along the annular gap between the inner wall of the outer tube and the outer wall of the middle tube, forming a low-temperature protective gas layer on the outer wall of the rectangular tube, which is used to prevent the rectangular tube from softening and cracking due to direct contact with the high temperature of the plasma. The laminar flow state of the low-temperature protective gas layer constrains the airflow disturbance on the outside of the middle tube, which is used to prevent the plasma from spreading outward and maintain the stable torch-shaped shape of the plasma.

[0013] According to one embodiment of the present invention, the sample introduction system includes a glass Scott-type dual-channel nebulizer, an external thermostatic circulator, a liquid cooling jacket, and a three-way mixing valve. The nebulizer is placed in the liquid cooling jacket, and the three-way mixing valve is used for online mixing of sample aerosol and auxiliary combustion gas. The spectral analysis unit includes a monochromator, a single-channel photomultiplier tube detector, and a signal processing module. The signal processing module has an integration time of 2-5 seconds for single-element signals.

[0014] On the other hand, the present invention also provides a method for detecting impurity elements in organic solutions, implemented based on the above-described apparatus, the method comprising the following steps: S1: Sample pretreatment, quantitatively diluting the organic solution to be tested with a specific organic solvent to make the sample viscosity consistent with that of the standard solution; S2: Stabilize sample injection and assist combustion. Start the cooling system to stabilize the temperature of the atomization chamber at 4℃. Mix the atomized sample aerosol with 1-3% v / v oxygen through a three-way mixing valve and then introduce it into the improved ICP rectangular tube. S3: Optimize plasma excitation, adopt a gradient power increase ignition program, with a radio frequency power range of 1.6-1.8kW, and continuously introduce low-flow oxygen into the carrier gas to form an online micro-oxidation environment; S4: Signal acquisition and background correction. Drive the monochromator to acquire the peak wavelength of the analytical line of the element to be measured and the background point wavelength signal. Use the two-point background correction method to deduct spectral interference. S5: Concentration determination: Based on the net intensity signal, the concentration of impurity elements is calculated using a calibration curve matched to the matrix.

[0015] According to one embodiment of the present invention, the organic solution to be tested includes any one of lubricating oil, kerosene, gasoline, diesel, and ethanol.

[0016] According to one embodiment of the present invention, in step S4, the integration time of the single-element signal is 2-5 seconds.

[0017] The innovative rectangular tube design in this invention employs three concentric tubes to form independent airflow channels, creating a synergistic effect with the gradient design of the working dimensions: the outer tube cooling gas ensures the structural safety of the rectangular tube and confines the plasma boundary; the middle tube auxiliary gas stabilizes the plasma morphology and isolates the high temperature from the central tube; the large-diameter central tube enables efficient sample guidance, while the yttrium oxide on the inner wall of the central tube (…) The coating can suppress carbon buildup and optimize the organic combustion environment; ultimately, it enables long-term stable and continuous operation of plasma, reduces the loss of the rectangular tube, and after the experiment, there is no obvious carbon buildup on the inner wall of the rectangular tube, which can meet the requirements for organic solution detection.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The collaboratively improved sample introduction system and rectangular tube design, combined with the gradient power ignition program and online micro-oxidation environment, significantly improve plasma stability, effectively prevent interruptions in the detection process, and allow for continuous operation for 8 hours without plasma flameout.

[0019] 2. The yttrium oxide coating on the inner wall of the rectangular tube, combined with the online micro-oxidation environment, significantly enhances the resistance to carbon buildup. After the experiment, there was no obvious carbon buildup on the inner wall of the rectangular tube, thus extending the service life of the core components.

[0020] 3. The combination of two-point background correction method and matrix matching technology effectively eliminates spectral interference and matrix effects. The relative standard deviation of 10 consecutive measurements is <3%, and the relative deviation compared with the standard method is within ±5%, ensuring detection accuracy.

[0021] 4. Simplifies sample pretreatment process, eliminates complicated operations, significantly improves analytical efficiency, is suitable for batch sample detection, has strong versatility, and can be adapted to various organic solutions with high viscosity and complex matrices. Attached Figure Description

[0022] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the ICP-OES device structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of plasma detection using a combination of a spectrophotometer system and a detector according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the rectangular tube structure according to an embodiment of the present invention; Figure 4 This is a schematic diagram of plasma combustion of a sample at the outlet of a rectangular tube, according to an embodiment of the present invention. Figure 5 This is a photograph of the plasma combustion of the sample at the outlet of the rectangular tube according to an embodiment of the present invention. Figure 6 This is a flowchart of the rectangular tube ICP-OES detection of impurity elements in organic solutions according to an embodiment of the present invention. Detailed Implementation

[0023] To facilitate a clear description of the technical solutions in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" are not necessarily different.

[0024] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0025] In this invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c" can represent: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0026] like Figure 1 The diagram shows a schematic of the ICP-OES device. The detection device of this invention includes an ICP system, a sample introduction system, and a spectral analysis unit.

[0027] The ICP system provides a high-temperature plasma environment for the ionization and excitation of samples. It includes a rectangular tube, an excitation power supply, and an excitation coil. The rectangular tube is the core improved component. The excitation coil is placed around the outside of the top of the rectangular tube and is electrically connected to the excitation power supply. Under the high-frequency excitation of the excitation power supply, the auxiliary gas (argon) is dissociated to generate argon ion plasma, forming a high-temperature plasma environment that ionizes impurity elements in the sample and emits characteristic wavelength light.

[0028] The sample introduction system enables the atomization, temperature stabilization, and online mixing of the organic solution to be tested, including a glass Scott-type dual-channel atomization chamber, an external temperature circulator, a liquid cooling jacket, and a three-way mixing valve. The components work together to achieve stable and efficient sample introduction.

[0029] The spectral analysis unit realizes the acquisition, detection, processing, and concentration calculation of characteristic spectral signals, including a monochromator, a single-channel photomultiplier tube (PMT) detector, and a signal processing module. like Figure 2 As shown, the characteristic spectrum emitted by the plasma generated at the rectangular tube outlet is introduced into the entrance slit of the monochromator. The monochromator acquires the specific wavelength spectrum of the combustion flame, and the photomultiplier tube detector receives the spectral signal. The signal processing module completes signal analysis and concentration calculation. The characteristic light is first collimated by a collimating component to eliminate stray light divergence interference, and then focused into parallel light by a focusing component. Inside the monochromator, the mixed spectrum is separated by wavelength through a grating, and the analytical line peak wavelength and background point wavelength spectrum of the analyte are selected separately and transmitted to the receiving end of the single-channel photomultiplier tube detector. The spectral acquisition range in the ultraviolet and infrared regions covers the main emission bands of the characteristic spectra of impurity elements in organic solutions.

[0030] To overcome the plasma extinction problem caused by the combustion of organic matter in organic solutions, this application improves the rectangular tube design, such as... Figure 3 The diagram shows a schematic of the rectangular tube structure. The rectangular tube employs a coaxial, nested, three-layer structure, consisting of three concentric quartz tubes: an outer tube, a middle tube, and a central tube, used to generate high-temperature plasma. The outer tube has a cooling gas inlet at its bottom, the middle tube has an auxiliary gas interface on its lower outer wall, and the central tube has a sample gas inlet at its bottom. The outer tube is the outermost layer, the middle tube is nested inside the outer tube, and the central tube is nested inside the middle tube. The axes of the three tubes coincide, forming two independent annular airflow channels and a central sample channel.

[0031] The cooling gas inlet at the bottom of the outer tube is connected to the cooling gas path, and the annular gap between the outer tube and the middle tube serves as the cooling gas channel. The auxiliary gas inlet at the lower part of the middle tube is connected to the auxiliary gas path, and the annular gap between the middle tube and the central tube serves as the auxiliary gas channel. The sample gas inlet of the central tube is connected to the outlet of the three-way mixing valve, and the inner cavity of the central tube serves as the sample aerosol channel. The output end of the central tube has a conical constriction structure. The cooling gas flows upward along the annular channel between the outer and middle tubes, forming a low-temperature protective gas layer on the outer wall of the rectangular tube. The auxiliary gas flows upward along the annular channel between the middle and central tubes, stabilizing the plasma morphology and ensuring the structural safety of the rectangular tube and the stability of the plasma.

[0032] The improved rectangular tube adopts a three-layer concentric quartz tube structure. The outer tube is used to introduce cooling gas and protect the torch tube from high temperature damage; the middle tube is used to introduce auxiliary gas, protect the central tube and help form a stable plasma; the central tube is used to introduce sample aerosol, and its diameter is increased to 2.5-3.5 mm. The yttrium oxide coating deposited on the inner wall can effectively block the adhesion of carbon-containing compounds and avoid carbon buildup affecting detection.

[0033] The rectangular tube adopts a coaxial nested three-layer concentric quartz tube structure, including an outer tube, a middle tube, and a central tube. The three tubes coincide in axis, forming two independent annular airflow channels and a central sample aerosol channel, realizing independent delivery and precise control of cooling gas, auxiliary gas, and sample gas. The inner diameter D of the central tube and the inner diameter d of the conventional rectangular tube meet the ratio relationship of D / d≥1.5. The range of the inner diameter d of the conventional rectangular tube is 1.5-2.0mm, and the preferred D / d ratio is 1.5-2.3 times. The inner diameter D of the central tube is specifically 2.5-3.5mm, providing sufficient space for the complete combustion of organic solution aerosols and solving the problems of clogging and incomplete combustion of high viscosity samples. The central tube has a conical constriction at its opening, with a taper of 15-30°, a constriction length of 3-5 mm, and an outlet diameter of 1.8-2.2 mm. The inner wall of the constriction smoothly transitions to the inner wall of the central tube. This constriction accelerates the aerosol flow rate, improves the contact efficiency between the sample and the plasma, and compensates for the sensitivity loss caused by the large-diameter central tube. The inner wall of the central tube is coated with 80-150 micrometers of yttrium oxide (YTO). The coating is prepared by plasma-enhanced chemical vapor deposition. The coating adhesion is ≥5MPa, which can effectively prevent carbon compounds from adhering to the pipe wall and inhibit carbon deposit formation. The central pipe and the inner wall of the middle pipe form an annular auxiliary gas channel with a width of 0.1-0.6mm and an effective working section length of 12-15mm. The inner diameter of the middle pipe is 4.0-6.0mm, and it forms an annular cooling gas channel with a width of 1.0-2.0mm with the inner wall of the outer pipe. The effective working section length is 15-18mm. An auxiliary gas interface is provided in the lower part of the outer wall of the central tube, which is sealed to the auxiliary gas path of the ICP system. The auxiliary gas (argon) flows upward along the annular auxiliary gas channel, stabilizing the plasma in the middle region of the rectangular tube. The flame core diameter of the plasma can be precisely controlled by adjusting the flow rate. The outer tube has an inner diameter of 6.5-10.0 mm and an effective working section length of 18-22 mm, which is compatible with the winding range of the excitation coil. The overall length of the outer tube is 45-55 mm. A cooling gas interface is located at the bottom of the outer wall of the outer tube, which is sealed to the cooling gas path of the ICP system. The cooling gas (argon) flows upward along the annular cooling gas channel, forming a low-temperature protective gas layer on the outer wall of the rectangular tube. This prevents the rectangular tube from softening and cracking due to direct contact with the high temperature of the plasma. Simultaneously, the laminar flow state of the low-temperature protective gas layer constrains the airflow disturbance on the outside of the central tube, preventing plasma from diffusing outward and maintaining the stable torch-like shape of the plasma. The large-diameter central tube solves the problem of insufficient combustion space, the narrowing compensates for sensitivity loss, the yttrium oxide coating inhibits carbon buildup, and the three-layer gas path achieves plasma stability.

[0034] Figure 4 A schematic diagram of the plasma combustion at the rectangular tube exit is provided. The plasma at the rectangular tube exit exhibits a torch-like layered structure, consisting of the following layers from the exit outwards: the atomization region, the atomic emission region, the ion emission region, and the tail flame. The atomization region, adjacent to the rectangular tube exit and located within the strong magnetic field of the working coil, has the highest temperature (approximately 6000-8000 K). Here, the sample aerosol is completely atomized, and the organic matrix is ​​fully combusted. The atomic emission region is located outside the atomization region, where atoms are stimulated to emit characteristic atomic spectra. The ion emission region, the middle layer of the plasma, has a moderate temperature (approximately 4000-6000 K). Atoms are further ionized into ions, which are stimulated to emit characteristic ion spectra. This region is the optimal detection area, with high spectral signal intensity and low interference. The tail flame, the outermost layer of the plasma, has the lowest temperature and no obvious emission signal; it represents the natural decay region of the plasma.

[0035] During the detection process, the monochromator's light inlet is precisely aligned with the ion emission region of the plasma, avoiding the high-temperature stray light from the atomization region and the weak signal region of the tail flame. This ensures that the acquired spectral signal has high intensity and a good signal-to-noise ratio, significantly improving the sensitivity and accuracy of the detection. At the same time, by combining the layered structure of the plasma, the winding position of the working coil and the radio frequency power are adjusted to maintain the stability of the ion emission region and avoid plasma morphology shift that could lead to detection position failure.

[0036] Figure 5This is a photograph of the plasma combustion at the outlet of the rectangular tube, visually demonstrating the stable, torch-like morphology of the plasma. The plasma core is straight, with clear boundaries, no drift or swaying, and no obvious carbon black smoke. This serves as direct verification of the effectiveness of the invention's technical solution, confirming the synergistic effect of the improved rectangular tube structure, online micro-oxidation environment, and gradient power ignition procedure: the stable torch-like plasma morphology proves that the invention effectively maintains the temperature gradient and airflow stability of the plasma, preventing plasma extinction; the absence of carbon black smoke proves that the yttrium oxide coating combined with oxygen-assisted combustion's anti-carbon deposition design effectively promotes complete combustion of the organic matrix and inhibits carbon particle formation. During testing, the plasma morphology shown in this attached figure can be used as a criterion for determining the device's successful commissioning. If the plasma exhibits the stable torch-like morphology shown in the attached figure after commissioning, sample testing can proceed, ensuring the stability of the testing process.

[0037] The atomization chamber is placed in a liquid cooling jacket, and an external thermostatic circulator is sealed to the liquid cooling jacket, which can accurately and stably control the temperature of the atomization chamber at the set value, reduce the volatilization loss of organic samples, and improve the stability of aerosols. The three-way mixing valve is connected to the gas outlet of the atomization chamber, the auxiliary combustion gas path (oxygen path), and the sample gas inlet of the rectangular tube center tube, respectively, to achieve online uniform mixing of the atomized sample aerosol and the auxiliary combustion gas, providing an oxidation environment for the complete combustion of organic solutions. The sample introduction system is also equipped with a peristaltic pump and a glass atomizer. The peristaltic pump provides stable power for sample delivery, and the glass atomizer atomizes the organic solution into aerosols with uniform particle size, ensuring full contact between the sample and the plasma.

[0038] The monochromator's inlet is directly aligned with the optimal plasma detection zone at the rectangular tube outlet, enabling precise acquisition of spectral signals from the peak wavelength of the analytical line and the background wavelength of the analyte, achieving effective separation of mixed spectra. The single-channel photomultiplier tube detector receives the spectral signal output from the monochromator, converts the optical signal into an electrical signal, and amplifies it, exhibiting high sensitivity and a high signal-to-noise ratio, suitable for trace element signal detection. The signal processing module is electrically connected to the photomultiplier tube detector, with the integration time for single-element signals set to 2-5 seconds. It also incorporates a two-point background correction algorithm to effectively deduct spectral interference, obtain the net intensity signal, and calculate the concentration of impurity elements by combining it with a matrix-matched calibration curve.

[0039] like Figure 6 As shown, a flowchart of ICP-OES detection of impurity elements in organic solutions is presented, demonstrating the complete detection process from sample preparation to result output. The detection method is implemented based on the improved ICP-OES device described above. Through steps such as sample pretreatment, stable sample introduction, plasma optimization excitation, signal acquisition and correction, and concentration calculation, accurate detection of impurity elements in organic solutions is achieved. The specific steps are as follows: S1: Sample pretreatment; Take the organic solution to be tested and quantitatively dilute it using a specific organic solvent that matches the sample matrix. Mix thoroughly to ensure that the viscosity of the diluted sample is consistent with that of the standard solution, thereby eliminating matrix interference caused by viscosity differences and improving the accuracy of the test results. The organic solution to be tested includes any one of lubricating oil, kerosene, gasoline, diesel, and ethanol. For high-viscosity lubricating oil, the preferred dilution ratio is 5-10 times. For low-viscosity organic solutions, the dilution ratio can be adjusted according to the actual situation.

[0040] S2: Stabilized sample introduction and assisted combustion; An external thermostatic circulator is activated to stabilize the temperature of the nebulization chamber at 4°C using a liquid cooling jacket, reducing the volatilization loss of organic sample aerosols. A peristaltic pump is then activated to deliver the diluted sample to the glass nebulizer, which atomizes the sample into aerosols with uniform particle size. After stabilization in the nebulization chamber, the aerosols are mixed online with 1-3% v / v oxygen via a three-way mixing valve. The mixture of sample aerosol and oxygen is then introduced into the central tube of a modified ICP rectangular tube. The oxygen serves as an auxiliary combustion gas, providing a micro-oxidation environment for the organic solution aerosols, promoting complete combustion of organic matter and preventing the formation of carbon particles.

[0041] S3: Optimize plasma excitation; The excitation power supply of the ICP system is started, and the plasma is ignited using a gradient power increase ignition program to avoid plasma instability caused by sudden temperature changes in the early stage of organic combustion. The radio frequency power is controlled within the range of 1.6-1.8kW. Low-flow-rate oxygen is continuously introduced into the carrier gas (argon) to form an online micro-oxidation environment in the plasma region, further suppressing carbon deposition. At the same time, by adjusting the flow rate of the auxiliary gas, the plasma is stabilized in the middle region of the rectangular tube to maintain a stable torch-shaped morphology, ensuring that impurity elements in the sample are fully ionized and excited.

[0042] S4: Signal acquisition and background correction; The spectral analysis unit is activated to drive the monochromator's grating to perform wavelength scanning, accurately acquiring the peak wavelength signal of the analytical line of the element to be measured and the background wavelength signal. The integration time of the single element signal is set to 2-5 seconds. The signal processing module receives the electrical signal transmitted by the photomultiplier tube detector and uses the two-point background correction method to subtract spectral interference. That is, by acquiring the signal intensity of the background points on both sides of the analytical line, the average background intensity is calculated and subtracted from the peak wavelength signal intensity to obtain the net intensity signal of the element to be measured.

[0043] S5: Concentration determination; The signal processing module performs quantitative calculations based on the net intensity signal obtained in step S4 and the matrix-matched calibration curve to directly obtain the concentration of each impurity element in the organic solution to be tested. The matrix-matched calibration curve is prepared using a standard solution with the same matrix composition as the sample to be tested to eliminate the influence of matrix effect on the detection results. The linear correlation coefficient of the calibration curve is ≥0.999.

[0044] Example 1: Detection of wear metal elements in lubricating oil; Sample preparation: Take 0.5g of lubricating oil sample, dilute it 5 times with pure base oil, mix thoroughly to ensure that the sample viscosity is consistent with the standard solution, and eliminate matrix interference caused by viscosity difference.

[0045] Rectangular tube selection: The installation center tube diameter is 3.0mm and the inner wall is reinforced with... Improved rectangular tube with coating; RF power: set to 1.7kW, with gradient temperature ramping mode used to start the excitation power supply; Cooling system: Activate the external thermostatic circulator to stabilize the temperature of the atomization chamber at 4℃; constant temperature reduces the loss of organic sample volatilization.

[0046] Assist gas: Adjust the oxygen flow rate to make the mixing ratio of sample aerosol and oxygen 2% v / v. The carrier gas is continuously introduced through a three-way mixing valve. The oxygen promotes the complete combustion of organic matter and avoids the formation of carbon particles.

[0047] Sample introduction and excitation: The peristaltic pump is started to deliver the diluted sample into the nebulizer. After the atomized sample aerosol is stabilized in the cooling nebulization chamber, it is mixed with oxygen and introduced into the rectangular tube. Under the action of gradient power, the oxygen in the carrier gas forms an online micro-oxidation environment. The gradient power avoids sudden temperature changes in the initial stage of organic combustion, and the micro-oxidation environment inhibits carbon deposition. The sample is fully combusted in the plasma, and the elements are excited to emit characteristic spectra.

[0048] Signal acquisition and correction: The driving monochromator sequentially acquires the peak wavelength of the analytical line and the background wavelength of the metal element to be measured, and the integration time of the single element signal is set to 3 seconds; the signal processing module uses the two-point background correction method to subtract spectral interference and obtain the net intensity signal.

[0049] Results Calculation and Output: Based on the net intensity signal and the calibration curve matched to the matrix, the concentration of each wear metal element in the lubricating oil is directly calculated, and the detection results are output.

[0050] In this experiment, the lubricating oil sample was measured 10 times consecutively, and the relative standard deviation was less than 3%, indicating that the method has good precision. Compared with the standard detection method, the relative deviation of the detection results of each element was within ±5%, and the accuracy met the detection requirements. During continuous operation, no plasma flameout occurred, indicating excellent system stability. After the experiment, the inner wall of the rectangular tube was inspected and no obvious carbon deposits were found, indicating outstanding anti-pollution properties.

[0051] The high viscosity of organic solutions makes atomization difficult; their flammability and intense exothermic combustion often lead to fluctuations in plasma temperature gradients; and incomplete combustion produces carbon particles, resulting in carbon buildup. Improved large-diameter rectangular tubes help address the spatial requirements of organic combustion, creating a suitable environment for complete combustion, but this can lead to decreased sensitivity. Further constriction accelerates aerosol flow and improves contact efficiency with the plasma, compensating for the sensitivity loss. A yttrium oxide coating on the inner wall of the rectangular tube prevents the adhesion of carbon particles generated during combustion; and the introduced oxygen further promotes complete organic combustion. The synergistic effect of these measures improves measurement stability and accuracy.

[0052] If only the diameter of the central tube is increased (without coating), the carbon particles generated by organic combustion will quickly adhere to the tube wall, leading to plasma instability; if only a yttrium oxide coating is applied (without a large diameter), the insufficient combustion space will cause local enrichment of organic matter, still producing a large number of carbon particles, which the coating cannot completely resist; if only a narrowing is set (without a large diameter), the sample aerosol will easily clog the central tube (especially high-viscosity lubricating oil), and the insufficient combustion space will lead to flameout.

[0053] By eliminating carbon buildup and plasma temperature fluctuations, continuous operation without plasma shutdown can be achieved, meeting the needs of batch sample testing. After the experiment, the inner wall of the rectangular tube showed "no obvious carbon buildup," effectively extending the lifespan of the core component, the rectangular tube. Because it can continuously and stably achieve more than 10 measurements, multiple measurements yield more stable and accurate results, effectively reducing the RSD (Responsive Displacement) index of repeated measurements.

[0054] The method and apparatus for detecting impurity elements in organic solutions of the present invention have a reasonable structural design, are easy to operate, have high detection accuracy and good stability. They can realize continuous and accurate detection of trace metal and non-metal impurity elements in various organic solutions such as lubricating oil, kerosene, gasoline, diesel, and ethanol, and solve the technical bottleneck of the prior art in the field of organic solution detection.

[0055] The device of this invention can be implemented by modifying existing ICP-OES equipment, resulting in low modification costs, strong compatibility, and no need to purchase new equipment. The detection method simplifies the sample pretreatment process, improves analytical efficiency, and reduces detection costs. This invention can be widely applied in product quality testing, production process monitoring, and equipment wear monitoring in industries such as petrochemicals, new energy, and fine chemicals, and has significant industrial application value and market prospects.

[0056] The large-diameter central tube provides ample space for the complete combustion of organic solution aerosols, solving the problems of clogging and incomplete combustion of high-viscosity samples, but it can easily lead to a decrease in sensitivity. The conical constriction structure at the opening of the central tube accelerates the aerosol flow rate, improves the contact efficiency between the sample and the plasma, and precisely compensates for the sensitivity loss caused by the large diameter. The yttrium oxide coating on the inner wall of the central tube can effectively prevent carbon particles from adhering. However, if only the coating is applied without a large-diameter combustion space, the local enrichment of organic matter will still produce a large number of carbon particles, and the coating cannot completely resist carbon buildup. The online micro-oxidation environment (oxygen-assisted combustion) promotes the complete combustion of organic matter, reduces the generation of carbon particles, and forms a double anti-carbon buildup protection with the yttrium oxide coating. The gradient power ignition program avoids plasma instability caused by sudden temperature changes in the early stage of organic combustion. The constant temperature control of the atomization chamber at 4℃ reduces the volatilization loss of organic aerosols. The flow rate regulation of the auxiliary gas stabilizes the plasma in the optimal detection zone. The three work together to maintain the stable torch-shaped shape of the plasma. The two-point background correction method effectively eliminates spectral interference, and the matrix matching technology eliminates matrix effects. The two work together to improve detection accuracy and achieve precise determination of trace elements.

[0057] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, disclosure, and other materials. In this specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple components. A single processor or other unit can implement several functions listed in the specification. While certain measures are described in different embodiments, this does not mean that these measures cannot be combined to produce good results.

[0058] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely illustrative of the invention and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications fall within the scope of the invention and its equivalents, the invention is also intended to include such modifications and modifications.

Claims

1. An apparatus for detecting impurity elements in organic solutions, comprising an ICP system, a sample introduction system, and a spectroscopic analysis unit, characterized in that, The ICP system includes a rectangular tube, an excitation power supply, and an excitation coil. The excitation coil is placed around the outside of the top of the rectangular tube. Under the excitation power supply, the auxiliary gas is dissociated to generate plasma, forming a high-temperature plasma environment that ionizes the elements in the sample and emits light. The rectangular tube comprises an outer tube, a middle tube, and a central tube, which are coaxially nested in a three-layer concentric structure. The inner diameter D of the central tube and the inner diameter d of the conventional rectangular tube satisfy a ratio of D / d≥1.

5. The inner diameter d of the conventional rectangular tube ranges from 1.5 to 2.0 mm. The central tube has a constriction structure at its opening. The constriction is conical with a taper of 15-30°. The constriction length is 3-5 mm, and the constriction outlet diameter is 1.8-2.2 mm. The inner wall of the constriction smoothly transitions to the inner wall of the central tube.

2. The apparatus according to claim 1, characterized in that, The inner wall of the central tube is coated with an 80-150 micrometer thick yttrium oxide coating, which is prepared by plasma-enhanced chemical vapor deposition and has an adhesion of ≥5 MPa.

3. The apparatus according to claim 1, characterized in that, The ratio D / d between the inner diameter D of the central tube and the inner diameter d of the conventional tube ranges from 1.5 to 2.

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4. The apparatus according to claim 1, characterized in that, The inner diameter D of the central tube is specifically 2.5-3.5mm, forming an annular auxiliary air channel with a width of 0.1-0.6mm with the inner wall of the central tube, and the effective working section length is 12-15mm.

5. The apparatus according to claim 4, characterized in that, The inner diameter of the middle tube is 4.0-6.0 mm, forming a 1.0-2.0 mm wide annular cooling air channel with the inner wall of the outer tube, and the effective working section length is 15-18 mm. The lower part of the outer wall of the central tube is provided with an auxiliary air interface, which is connected to the auxiliary air circuit of the ICP system. The auxiliary gas flows upward along the annular gap between the inner wall of the middle tube and the outer wall of the central tube, which is used to stabilize the plasma in the middle region of the rectangular tube and to regulate the flame core diameter of the plasma by adjusting the flow rate.

6. The apparatus according to claim 5, characterized in that, The inner diameter of the outer tube is 6.5-10.0 mm, the effective working section length is 18-22 mm, which is compatible with the winding range of the excitation coil of the ICP system, and the overall length is 45-55 mm. The cooling gas interface at the bottom of the outer wall of the outer tube is sealed to the cooling gas path of the ICP system. The cooling gas flows upward along the annular gap between the inner wall of the outer tube and the outer wall of the middle tube, forming a low-temperature protective gas layer on the outer wall of the rectangular tube. This layer is used to prevent the rectangular tube from softening and cracking due to direct contact with the high temperature of the plasma. The laminar flow state of the low-temperature protective gas layer constrains the airflow disturbance on the outside of the middle tube, thereby preventing the plasma from spreading outward and maintaining the stable torch-shaped shape of the plasma.

7. The apparatus according to claim 1, characterized in that, The sample introduction system includes a glass Scott-type dual-channel nebulizer, an external thermostatic circulator, a liquid cooling jacket, and a three-way mixing valve. The nebulizer is placed in the liquid cooling jacket, and the three-way mixing valve is used for online mixing of sample aerosol and auxiliary combustion gas. The spectral analysis unit includes a monochromator, a single-channel photomultiplier tube detector, and a signal processing module. The signal processing module has an integration time of 2-5 seconds for single-element signals.

8. A method for detecting impurity elements in an organic solution, implemented based on the apparatus according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Sample pretreatment, quantitatively diluting the organic solution to be tested with a specific organic solvent to make the sample viscosity consistent with that of the standard solution; S2: Stabilize sample introduction and assist combustion. Start the cooling system to stabilize the temperature of the atomization chamber at 4℃. Mix the atomized sample aerosol with 1-3% v / v oxygen through a three-way mixing valve and then introduce it into the improved ICP rectangular tube. S3: Optimize plasma excitation, adopt a gradient power increase ignition procedure, with a radio frequency power range of 1.6-1.8kW, and continuously introduce low-flow oxygen into the carrier gas to form an online micro-oxidation environment; S4: Signal acquisition and background correction. Drive the monochromator to acquire the peak wavelength of the analytical line of the element to be measured and the background point wavelength signal. Use the two-point background correction method to deduct spectral interference. S5: Concentration determination: Based on the net intensity signal, the concentration of impurity elements is calculated using a calibration curve matched to the matrix.

9. The method according to claim 8, characterized in that, The organic solution to be tested includes any one of lubricating oil, kerosene, gasoline, diesel, and ethanol.

10. The method according to claim 8, characterized in that, In step S4, the integration time for a single-element signal is 2-5 seconds.

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