S-shaped platform peak area measuring method for gas phase molecule absorption spectrum analysis

Abstract

The invention discloses an S-shaped platform peak area measurement method for gas phase molecular absorption spectrum analysis, and relates to the technical field of spectral analysis, the stability and accuracy of measurement are ensured through the steps of preheating an instrument, preparing a carrier liquid, accurately controlling the flow velocity and pump velocity of a carrier and the like; a standard curve is used for calibration, so that the measurement precision is further improved; the whole process is controlled by operation software of the full-automatic gas-phase molecular absorption spectrometer, so that human intervention is reduced, and the measurement efficiency and consistency are improved; automatic sampling, cleaning, air blowing and other steps are adopted, so that the operation process is simplified, and the operation difficulty is reduced; by means of the gas-liquid separation reaction coil pipe and the gas-liquid separation bottle, effective separation of gas and liquid is achieved, and interference of the liquid on gas measurement is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of spectral analysis, and in particular to a method for measuring the area of an S-shaped platform peak in gas-phase molecular absorption spectroscopy. Background Art

[0002] In the current gas-phase molecular absorption spectroscopy, the core step is to mix the water sample with a specific chemical reagent, and by means of a rapid chemical reaction mechanism, convert the component to be analyzed into a gas state. Subsequently, within a specific spectral wavelength range, the peak height absorbance value of these gas molecules is measured, and this value is proportional to the concentration of the component to be measured, thereby achieving precise quantitative analysis of each component in the water sample.

[0003] However, during this process, the component to be measured is gradually released as gas molecules from the reaction system, which results in generally low absorbance of the gas molecules. Especially when analyzing low-content components in the water sample, if the peak height absorbance value drops below 0.00X Abs, the repeatability of the measurement results will be greatly reduced, and it is even difficult to accurately measure.

[0004] It is worth noting that on March 9, 2023, a patented technology regarding peak area was published. Although its detection sensitivity is improved compared to peak height absorbance, with an increase of about 5 to 6 times, both peak area absorption and peak height absorption exhibit a symmetric spike shape.

[0005] In terms of actual operation, the gas-phase molecular absorption spectroscopy usually adopts a continuous injection method to obtain a stable S-shaped platform peak height absorbance. This method is easy to master, can generate an accurate standard curve, and ensure that the accuracy and precision of sample determination both reach a relatively high level. However, its disadvantage is that the consumption of samples and reagents is much higher than that of the symmetric peak height absorbance method.

[0006] In order to further improve the measurement effect of absorbance, the present patent innovatively proposes to convert the area of the S-shaped platform peak into absorbance for calculation. The practical results prove that by calculating the absorbance of the square area through the product of the peak height h and the measurement time s, the principle of this method strictly follows Beer's law and can ensure the accuracy of water sample component determination. For the above problems, there may already be technical means to solve them in the prior art, but this case wants to provide an alternative or replacement technical solution. Summary of the Invention

[0007] The technical solution of the present invention to achieve the above object is: a method for measuring the area of an S-shaped platform peak in gas-phase molecular absorption spectroscopy, characterized by including the following operating steps:

[0008] Step S1: Preheat the water sample pump, carrier liquid pump, and carrier gas pump for about 30 min;

[0009] Step S2: Prepare the chemical reagent carrier solution in a beaker, then mix it thoroughly and introduce gas to perform sufficient mixing and aeration to expel the blank.

[0010] Step S3: Insert the sampling tube into the bottom of the beaker containing the carrier solution, and insert the liquid suction needle tube of the automatic sampler into the bottom of the standard solution test tube on the sampling tray in sequence, and introduce carrier gas (air) at a flow rate of 0.2 L / min.

[0011] Step S4: Start the water sample pump and the carrier solution pump. After the water sample and the carrier solution are mixed, introduce the carrier gas and enter the gas-liquid separation reaction coil. Under the action of the carrier gas, a chemical reaction occurs, and the generated gas enters the absorption tube through the water removal device, and the absorbance of the gas is measured at the emission wavelength of the hollow cathode lamp.

[0012] Step S5: The carrier solution, the water sample and the carrier gas enter the gas-liquid separation reaction coil through a three-way pipe, and the gas and liquid generated by the physical and chemical reaction in the gas-liquid separation reaction coil enter the gas-liquid separation bottle.

[0013] Step S6: The waste liquid entering the gas-liquid separation bottle is automatically discharged into the waste liquid bucket through the drain pipe; the generated gas removes moisture through the cold trap and enters the absorption tube to measure the absorbance; according to the absorbance generated by the gas, the content of the measured component in the water sample is automatically calculated from the standard curve.

[0014] Step S7: Draw the standard curve of the measured component, then measure the absorbance of the gas generated in the water sample, and calculate the content of the water sample component according to the standard curve.

[0015] In the said Step S1, start the measurement when the baseline drift is less than or equal to one ten-thousandth within 90 s of the instrument.

[0016] The pump speed of the carrier gas pump: 70 revolutions / min, and the carrier gas flow rate is 0.2 L / min.

[0017] In the said Step S4, the content of the measured component in the water sample is automatically measured and calculated by the operation software of the fully automated gas-phase molecular absorption spectrometer throughout the process.

[0018] The gas-liquid separation reaction coil: a polytetrafluoroethylene reaction tube with an inner diameter Ф = 2 mm and a length L = 100 cm.

[0019] The carrier solution: Add 500 ml of 20% hydrochloric acid to a 1-liter beaker, and then pour the solution back and forth 5 - 6 times between another 1-liter beaker at a distance to expel the sulfide blank in the reagent.

[0020] In step S3, 20 ml of each sulfide standard solution is prepared in 6 calibrated test tubes with lids, each having a capacity of 20 ml. The pipette is inserted into the carrier liquid reagent bottle, and the water sample pipette is automatically inserted into the sulfide standard solution and the water sample tubes on the auto-sampler in sequence. Then, start the fully automated gas-phase molecular absorption spectrometer (produced by Shanghai Anjie Zhichuang Technology Co., Ltd.) to automatically measure the standard solution and the water sample.

[0021] For the fully automated gas-phase molecular absorption spectrometer, the injection and cleaning liquid path time is 30 s, the purging gas path time is 15 s, and the injection and measurement time is 35 s.

[0022] The working timing of the carrier gas pump is as follows: cleaning for 30 s, purging for 20 s, injection for 35 s, and carrier gas for 35 s.

[0023] In step S7, multiply the measured absorption peak height h by the rectangular area covered by the measurement time s to obtain the absorbance value. The method principle conforms to Beer's law.

[0024] A method for measuring the S-shaped platform peak area in gas-phase molecular absorption spectroscopy using the technical solution of the present invention, compared with the prior art: by steps such as preheating the instrument, preparing the carrier liquid, precisely controlling the carrier gas flow rate and pump speed, etc., it ensures the stability and accuracy of the measurement; using a standard curve for calibration further improves the measurement accuracy; the whole process is controlled by the operation software of the fully automated gas-phase molecular absorption spectrometer, reducing human intervention and improving the measurement efficiency and consistency; automated injection, cleaning, purging and other steps simplify the operation process and reduce the operation difficulty; through the gas-liquid separation reaction coil and the gas-liquid separation bottle, effective separation of gas and liquid is achieved, avoiding interference of liquid on gas measurement; the moisture removal step of the cold trap further ensures the accuracy of gas measurement; this method is applicable to the measurement of specific components in various water samples, such as sulfide, etc., and has a wide application prospect; the method principle conforms to Beer's law, that is, the absorbance is proportional to the substance concentration, providing theoretical support for the accuracy of the measurement; by measuring the rectangular area covered by the absorption peak height and the measurement time to calculate the absorbance value, it further improves the scientificity and reliability of the measurement; the waste liquid is automatically discharged into the waste liquid bucket through the drain pipe, facilitating subsequent treatment and meeting environmental protection requirements; by precisely controlling the carrier gas flow rate and pump speed, and optimizing the operation steps, the energy consumption is reduced. Detailed implementation mode

[0025] Persons in the art should connect all the electrical components in this case to their adapted power supplies through wires, and should select a suitable controller according to the actual situation to meet the control requirements. For the specific connection and control sequence, reference should be made to the sequence of the electrical components working in sequence in the following working principle to complete the electrical connection. The detailed connection means are well-known techniques in the art. The following mainly introduces the working principle and process, and will not explain the electrical control.

[0026] Example 1

[0027] Determination of sulfide in water

[0028] ① Fully automated gas phase molecular absorption spectrometer, produced by Shanghai Anjie Zhichuang Technology Co., Ltd.;

[0029] ② Gas-liquid separation reaction coil: PTFE reaction tube with inner diameter Ф = 2 mm and length L = 100 cm;

[0030] ③ Carrier solution: Add 500 ml of 20% hydrochloric acid to a 1-liter beaker, and then pour the solution back and forth 5 - 6 times between another 1-liter beaker to remove the sulfide blank in the reagent.

[0031] ④ Prepare 20 ml of 6-point sulfide standard solution in each of 6 20-ml graduated test tubes with lids. Insert the pipette 1 into the carrier solution reagent bottle, and insert the water sample pipette into the sulfide standard solution and water sample tubes on the automatic sampler in sequence. Start the instrument to automatically measure the standard solution and water sample.

[0032] (2) Measurement conditions

[0033] ① Preheat the instrument for about 30 min, and start the measurement when the baseline drift is less than or equal to one ten-thousandth within 90 s of the instrument;

[0034] ② Injection pump speed: 70 revolutions / min;

[0035] ③ Carrier gas flow rate 0.2 L / min,

[0036] ④ Injection cleaning liquid path time 30 s, purging gas path time 15 s, injection and measurement time: 35 s.

[0037] (3) Implementation operation and implementation results

[0038] Set the instrument in the [peak area] measurement mode. After measuring the absorbance of the [S-shaped plateau peak area] of each component standard solution according to the operation requirements of the claim book and plotting the standard curve, measure the absorbance of the water sample, and calculate the content of each component from the standard curve.

[0039] Example 2

[0040] Determination of nitrite nitrogen in water

[0041] (1) Instruments and equipment

[0042] Except that the carrier solution used is 0.4 mol / L citric acid solution, other equipment is the same as that for the determination of sulfide;

[0043] (2) The measurement conditions and implementation operations are the same as those for the determination of sulfide;

[0044] (3) Implementation results;

[0045] (4) The blank water was repeatedly measured 6 times, the standard deviation RSD = 0.0016, 0.0016 multiplied by 3 and divided by the standard curve slope of 4.5094, the detection limit of nitrite nitrogen = 0.0011 mg / L

[0046] The above technical solutions only reflect the preferred technical solutions of the technical solutions of the present invention. Some changes that those skilled in the art of the present technology may make to some parts thereof all reflect the principles of the present invention and fall within the protection scope of the present invention.

Claims

1. A method for measuring the peak area of the S-shaped platform in gas-phase molecular absorption spectrometry, characterized in that, It includes the following operation steps: Step S1: Preheat the water sample pump, carrier liquid pump, and carrier gas pump for about 30 min; Step S2: Prepare the chemical reagent carrier liquid in a beaker, then mix it thoroughly and introduce gas, mix and aerate it fully to expel the blank; Step S3: Insert the sampling tube into the bottom of the beaker containing the carrier liquid, and automatically insert the liquid suction needle tube of the automatic sampler into the bottom of the standard liquid test tube on the sampling tray in sequence, and introduce carrier gas at a flow rate of 0.2 L / min; Step S4: Start the water sample pump and carrier liquid pump. After the water sample and carrier liquid are mixed, introduce the carrier gas, enter the gas-liquid separation reaction coil, and carry out a chemical reaction under the action of the carrier gas. The generated gas enters the absorption tube through the water removal device, and the absorbance of the gas is measured at the emission wavelength of the hollow cathode lamp; Step S5: The carrier liquid, water sample, and carrier gas enter the gas-liquid separation reaction coil through a three-way pipe. The gas and liquid generated by the physical and chemical reaction in the gas-liquid separation reaction coil enter the gas-liquid separation bottle; Step S6: The waste liquid entering the gas-liquid separation bottle is automatically discharged into the waste liquid bucket through the drain pipe; the generated gas removes moisture through the cold trap and enters the absorption tube to measure the absorbance; according to the absorbance generated by the gas, the content of the measured component in the water sample is automatically calculated from the standard curve; Step S7: Draw the standard curve of the measured component, then measure the absorbance of the gas generated in the water sample, and calculate the content of the water sample component according to the standard curve.

2. The method for measuring the S-shaped platform peak area in gas-phase molecular absorption spectrometry according to claim 1, wherein, In step S1, start the measurement when the baseline drift is less than or equal to one ten-thousandth within 90 s of the instrument.

3. The method for measuring the S-shaped platform peak area in gas-phase molecular absorption spectrometry according to claim 2, wherein, The pump speed of the carrier gas pump: 70 revolutions / min, and the carrier gas flow rate: 0.2 L / min.

4. The method for measuring the S-shaped platform peak area in gas-phase molecular absorption spectrometry according to claim 3, characterized in that, In step S4, the content of the measured component in the water sample is automatically measured and calculated by the operation software of the fully automated gas-phase molecular absorption spectrometer throughout the process.

5. A method for measuring the peak area of the S-shaped platform in gas-phase molecular absorption spectrometry according to claim 4, characterized in that, The gas-liquid separation reaction coil: a polytetrafluoroethylene reaction tube with an inner diameter Ф = 2 mm and a length L = 100 cm.

6. The method for measuring the S-shaped platform peak area in gas-phase molecular absorption spectrometry according to claim 5, wherein, The carrier liquid: Add 500 ml of 20% hydrochloric acid to a 1-liter beaker, and then pour the solution back and forth 5 - 6 times between two 1-liter beakers at a distance to expel the sulfide blank in the reagent.

7. A method for measuring the peak area of the S-shaped platform in gas-phase molecular absorption spectrometry according to claim 6, characterized in that, In step S3, prepare 20 ml of sulfide standard solution in each of 6 20-ml capped graduated test tubes; insert the liquid suction tube into the carrier liquid reagent bottle, and the water sample suction tube is automatically inserted into the sulfide standard liquid and water sample tubes on the automatic sampling tray in sequence, and start the fully automated gas-phase molecular absorption spectrometer to automatically measure the standard liquid and water sample.

8. A method for measuring the peak area of the S-shaped platform in gas-phase molecular absorption spectroscopy according to claim 7, characterized in that, The injection cleaning liquid path time of the fully automated gas-phase molecular absorption spectrometer is 30 s, the blowing and purifying gas path time is 15 s, and the injection and measurement time: 35 s.

9. The method for measuring the S-shaped platform peak area in gas-phase molecular absorption spectrometry according to claim 8, characterized in that, The working time sequence of the carrier gas pump: cleaning for 30 s, blowing for 20 s, injection for 35 s, and carrier gas for 35 s.

10. A method for measuring the S-shaped platform peak area in gas-phase molecular absorption spectrometry according to claim 9, characterized in that, In step S7, multiply the measured absorption peak height h by the rectangular area covered by the measurement time s to obtain the absorbance value, and the method principle conforms to Beer's law.