WO2024016761A1

WO2024016761A1 - Gas chromatography-mass spectrometry analysis method for haloacetic acid in drinking water

Info

Publication number: WO2024016761A1
Application number: PCT/CN2023/089363
Authority: WO
Inventors: 李加付; 梁晓军; 张增利
Original assignee: 苏州大学
Priority date: 2022-07-20
Filing date: 2023-04-20
Publication date: 2024-01-25
Also published as: CN115236229A

Abstract

A gas chromatography-mass spectrometry (GC-MS) analysis method for haloacetic acid in drinking water, comprising the following steps: (1) taking a water sample of drinking water, adding a residual chlorine quenching agent for quenching, extracting haloacetic acid from the drinking water by using an organic solvent, and preparing a sample solution; (2) by taking the haloacetic acid as a standard substance and using the organic solvent as a solvent, diluting step by step to prepare a mixed standard solution; (3) respectively testing and analyzing the mixed standard solution and the sample solution by using a GC-MS instrument; and (4) drawing a standard curve according to the test and analysis result in step (3), and performing sample analysis. A quantification method for haloacetic acid in drinking water is established by using GC-MS, so that the defects of a standard method provided by the U.S. Environmental Protection Agency (USEPA, 552.3), a matching method provided in the Standards for Drinking Water Quality of China (GB/T5749-2006), and a diazomethane derivatization method are overcome, and one-step liquid-liquid extraction is achieved; on-machine quantification can be achieved after simple derivatization, and high sensitivity, a high recovery rate, a low method detection limit and a low quantification limit are achieved.

Description

A gas chromatography-mass spectrometry method for analyzing haloacetic acid in drinking water

Technical field

The invention relates to the technical field of analytical chemistry, and in particular to a gas chromatography-mass spectrometry analysis method of haloacetic acid in drinking water.

Background technique

Haloacetic acid is the most common disinfection by-product in drinking water. Its concentration in drinking water is usually at a pollution level of tens to hundreds of μg/L. It is the most carbon-containing disinfection by-product (C) after trihalomethane. -DBPs). However, haloacetic acid is more toxic than trihalomethanes and less volatile, so its threat to drinking water safety and human health deserves more attention. In the "Hygienic Standards for Drinking Water" (GB/T5749-2006) promulgated in 2006, my country limits dichloroacetic acid and trichloroacetic acid, with the maximum limits being 50 μg/L and 100 μg/L respectively. Establishing a sensitive, simple, and efficient analytical method for haloacetic acid is the basis for understanding the pollution status of this type of substance in drinking water and its potential human health risks.

Currently, there are many methods for measuring haloacetic acid. The most mainstream methods are the standard method provided by the U.S. Environmental Protection Agency (USEPA, 552.3) and the supporting method of China's "Drinking Water Quality Standards" (GB/T5749-2006). All species used acidified methanol to derivatize haloacetic acid, and then detected it with gas chromatography-electron capture detector (GC-ECD). This method has the problems of complex process, low enrichment factor, high detection limit, and low recovery rate of monochloroacetic acid, so it needs further improvement. Diazomethane derivatization is also a commonly used method for the detection of haloacetic acid. It effectively overcomes the problems of low haloacetic acid enrichment ratio, high detection limit and low monochloroacetic acid recovery rate in USEPA552.3 and GB/T5749-2006. However, The preparation of diazomethane requires a complicated process, and the generated diazomethane is prone to explosion and difficult to preserve, so it is not an ideal alternative.

At present, many researchers at home and abroad have improved the standard methods. For example, Ding Liping and others "A gas chromatography method for the determination of nine trace amounts of haloacetic acids in bottled drinking water (application publication number: CN 109212050 A)" is disclosed. This method uses hydroxymethylsulfonate-magnesium aluminum hydrotalcite to enrich haloacetic acid by dispersive solid phase extraction, then uses acid to dissolve the adsorbent to elute the haloacetic acid, and then uses an organic solvent to remove the haloacetic acid from the aqueous solution. The acetic acid is extracted into an organic solvent, and then the haloacetic acid is derivatized with methanol and trimethylsilylated diazomethane n-hexane, and finally detected by GC-ECD. This method uses hydroxymethane sulfonate-magnesium aluminum hydrotalcite for extraction. The material is not easy to obtain and the price is not low, so it is not economical. Secondly, this method involves multiple extractions and elutions as well as relatively complex derivatization, making the process cumbersome. In addition, the sample is measured using GC-ECD. Since there is no mass spectrometry, it is easily affected by matrix interference and false positives occur. For most haloacetic acids, the detection limit and quantitation limit of this method are too high and not sensitive enough, especially For monochloroacetic acid, the limit of quantification is as high as 3.1 μg/L, which is much higher than its actual concentration in drinking water.

Duan Jinming and others published the "Rapid detection method of haloacetic acid, a disinfection by-product in drinking water (Application Publication Number: CN 102520083 A)". This method does not require pretreatment and directly uses liquid chromatography mass spectrometry to detect haloacetic acid in drinking water, and obtains a very low limit of quantification (0.05-0.86 μg/L). However, based on the patent drawings and attempts, it can be seen that the method published by the author has obvious flaws. First, because there is no enrichment, it is difficult for the mass spectrometer to respond at such a low concentration. Moreover, the quantification limit of this method is also applicable to liquid chromatography mass spectrometry analysis as reported in the literature, but the sample is basically consistent after hundreds of times enrichment. In addition, we can see from the author's figure that most haloacetic acids have basically no response, and the abundance of the noise peak is basically consistent with the target compound.

Contents of the invention

In view of the shortcomings of the existing technology, the present invention provides a gas chromatography-mass spectrometry method for analyzing haloacetic acid in drinking water. Compared with existing analysis methods, the method of the present invention is simple and highly sensitive, and can be used in drinking water. Precise determination of haloacetic acids.

The purpose of the present invention is achieved through the following technical solutions:

The invention provides a gas chromatography-mass spectrometry analysis method for haloacetic acid in drinking water, which includes the following steps:

(1) Take a drinking water sample, add residual chlorine quenching agent for quenching, use an organic solvent to extract haloacetic acid in the drinking water, and prepare a sample solution;

(2) Use haloacetic acid as the standard substance, use organic solvents as the solvent, and prepare a mixed standard solution through gradual dilution;

(3) Use gas chromatography-mass spectrometry to detect and analyze the mixed standard solution and sample solution respectively;

(4) Draw a standard curve and perform sample analysis based on the detection and analysis results in step (3).

In one embodiment of the present invention, in step (1), the haloacetic acid in the drinking water is a disinfection by-product obtained by disinfecting the drinking water.

In one embodiment of the present invention, in step (1), the organic solvent is selected from one or more of methyl tert-butyl ether, n-hexane and ethyl acetate.

In one embodiment of the present invention, the specific steps of step (1) are: take a drinking water sample, measure the residual chlorine in the water, add a residual chlorine quenching agent for quenching, adjust the pH to acidic, and add the sample Internal standard and derivatization reagent to obtain sample solution.

In one embodiment of the invention, the pH<1.

In one embodiment of the invention, the derivatization reagent is selected from silylation reagents.

In one embodiment of the invention, the silanization reagent is selected from bis(trimethylsilyl)trifluoroacetamide, N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide , one or more of trimethylchlorosilane, hexamethyldisilazane and N,N dimethylformamide.

In one embodiment of the present invention, the residual chlorine quenching agent is ascorbic acid and/or ammonium chloride.

In one embodiment of the present invention, the derivatization conditions of the derivatization reagent are: heating temperature 25°C-80°C, reaction time 10min-30min.

In one embodiment of the present invention, in step (2), the haloacetic acid is selected from the group consisting of monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, dibromoacetic acid, monochloromonobromoacetic acid and monoiodoacetic acid. one or more of them.

In one embodiment of the present invention, in step (3), the gas in the gas chromatograph-mass spectrometer The phase chromatography analysis conditions are as follows: the chromatographic column is an HP-5ms chromatographic column, the carrier gas is helium, and the carrier gas flow rate is 1mL/min-2mL/min; the inlet temperature is 200°C-280°C; splitless injection is used. The injection volume is 1 μL-2 μL; the temperature rising program: the initial temperature is 35°C and held for 2 minutes, then raised to 100°C at a rate of 4°C/min and held for 2 minutes, then raised to 130°C at a rate of 9°C/min and held for 1 minute. , and finally the temperature was raised to 280°C at a speed of 12°C/min, and the final running time was 3 minutes.

The principle of the preparation method of this method is as follows:

The present invention uses liquid-liquid extraction to enrich seven common haloacetic acids in drinking water, and then selects silane reagents for derivatization. The reaction mechanism is shown in formula (1). Selected ion (SIM) analysis methods for seven haloacetic acids were established by optimizing the capillary chromatography column, inlet temperature, heating program, and characteristic ions of haloacetic acid. An efficient, simple and sensitive analysis method is provided for the detection of haloacetic acid in drinking water.

The technical solution of the present invention has the following advantages:

(1) The present invention uses silane reagents to replace the active hydrogen in the haloacetic acid molecules, reducing the polarity of the haloacetic acid and increasing the volatility of the haloacetic acid, so that it can be analyzed by gas chromatography-mass spectrometry.

(2) The method of the present invention avoids the complex process of diazomethane and acidified methanol derivatization methods, saving analysis time and chemical reagents.

(3) The method of the present invention has high sensitivity, low method detection limit and quantification limit, and can be used for analysis of highly toxic trace haloacetic acids in drinking water, such as monochloroacetic acid and monoiodoacetic acid.

(4) The method of the present invention uses mass spectrometry for quantification and avoids the false positive problem of the GC-ECD method.

(5) The present invention provides a gas chromatography-mass spectrometry analysis method for haloacetic acid in drinking water, and establishes a quantitative method for haloacetic acid in drinking water using GC-MS. Compared with the existing technology, this invention overcomes the standard method provided by the United States Environmental Protection Agency (USEPA, 552.3) and the supporting method of China's "Drinking Water Quality Standard" (GB/T5749-2006) and the diazomethane derivatization method. The disadvantages are realized One-step liquid-liquid extraction can be used for quantification after simple derivatization, and high sensitivity, high spike recovery, low method detection limit, and low quantitation limit are obtained. The method of the invention can be used to efficiently, quickly and accurately measure haloacetic acid in drinking water.

Description of drawings

In order to make the content of the present invention easier to understand clearly, the present invention will be further described in detail below based on specific embodiments of the present invention and in conjunction with the accompanying drawings, wherein

Figure 1 is a total ion chromatogram of haloacetic acid in drinking water in Example 1 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific examples, so that those skilled in the art can better understand and implement the present invention, but the examples are not intended to limit the present invention.

Example 1

(1)Sample collection

Collect tap water samples from 12 urban households in Suzhou City. Before collection, the water was drained for 3 minutes to ensure that the collected samples were tap water from the pipe network. Then, the brown glass bottles were washed three times with tap water, and then 500 mL of tap water was collected at each point. After water samples are collected, they are immediately transported to the laboratory for storage at low temperature (8°C).

(2)Liquid-liquid extraction

After using DPD reagent to measure the residual chlorine in the water, add ascorbic acid with a residual chlorine content of 110% (molar concentration) to quench, and then add 1 mL of concentrated sulfuric acid to make the pH of the solution <1. Take 100 mL of the aqueous solution and transfer it to a 125 mL brown glass bottle, then add 15 g of anhydrous sodium sulfate and 8 mL of methyl tert-butyl ether. After shaking for 1 minute, transfer to a 15 mL glass test tube. This process was repeated twice and the organic phases were combined. Add 5g of anhydrous sodium sulfate to the organic phase to remove the water in the solution, then transfer the organic phase to a new glass test tube, blow with nitrogen and concentrate to 0.2mL at room temperature, and then transfer to a 2mL tube with an inner Into the inserted injection bottle, add 5 μL of injection internal standard (1,2-dibromopropane) and 10 μL of silanization reagent, and then react in an oven at 50°C for 30 minutes. After the reaction is completed, cool to room temperature and wait for instrument analysis.

(3)Instrumental analysis

Samples were analyzed using an Agilent 7890 gas chromatograph-5977 mass spectrometer. The specific parameters are as follows: The chromatographic column is HP-5ms column (model 30m x 0.25mm x 0.25μm). The carrier gas is ultra-high purity helium (purity greater than 99.999%), the carrier gas flow rate is 1 mL/min; the inlet temperature is 250°C; splitless injection is used, and the injection volume is 1 μL.

The heating program of the column oven is as follows: the initial temperature is 35°C and held for 2 minutes, then raised to 100°C at a rate of 4°C/min and held for 2 minutes, then raised to 130°C at a rate of 9°C/min and held for 1 minute, and finally The temperature is raised to 280°C at a speed of 12°C/min, and the final running time is 3 minutes. The mass spectrometer ion source temperature is 230°C, the quadrupole temperature is 150°C, and the electron energy is 70eV. Selected ion (SIM) mode was used for sample analysis. The quantitative ion and qualitative ion information of the seven haloacetic acids are shown in Table 1 and Figure 1. After the instrument setting is completed, use the standard substance of haloacetic acid to determine the retention time, and then use the mixed standard to draw a standard curve. For details, see working curve drawing.

Table 1 Retention time, quantitative ion, qualitative ion, method detection limit and quantification limit (μg/L) of haloacetic acid in drinking water

It can be seen from Table 1 and Figure 1 that this method has good sensitivity. The detection limits and quantification limits of the seven haloacetic acids are mostly lower than 0.05 μg/L, which is much lower than the mainstream haloacetic acid analysis method (U.S. The standard method provided by the State Environmental Protection Administration (USEPA, 552.3) and the supporting method of China's "Drinking Water Quality Standards" (GB/T5749-2006) and the diazomethane derivatization method), but the processing process of this method is far better than the mainstream The method for analyzing haloacetic acids is simple. In addition, 7 kinds of haloacetic acids were analyzed on the HP-5 chromatographic column. It has good peak shape and response (Figure 1), indicating that it is an ideal chromatographic column for haloacetic acid analysis.

(4) Working curve drawing

Purchase a mixed standard of haloacetic acid (1000 mg/L), and then dilute it with methyl tert-butyl ether into 20 mg/L, 2 mg/L and 1 mg/L solutions. Take 8 clean 125mL brown glass bottles, add 100mL of ultrapure water, and then use the above diluted solution to prepare a concentration of 0.01μL, 0.05μL, 0.1μL, 0.5μL, 1μL, 5μL, 10μL, and 20μL. Haloacetic acid solution. After acidification with concentrated sulfuric acid, 15 g of anhydrous sodium sulfate and 8 mL of methyl tert-butyl ether were added. After shaking for 1 minute, transfer to a 15 mL glass test tube. This process was repeated twice and the organic phases were combined. Add 5g of anhydrous sodium sulfate to the organic phase to remove the water in the solution, then transfer the organic phase to a new glass test tube, blow with nitrogen and concentrate to 0.2mL at room temperature, and then transfer to a 2mL tube with an inner Into the inserted injection bottle, add 5 μL of injection internal standard (1,2-dibromopropane) and 10 μL of silanization reagent, and then react in an oven at 50°C for 30 minutes. After the reaction is completed, cool to room temperature and wait for instrument analysis. After measurement by a gas chromatography mass spectrometer, the peak area of haloacetic acid is used as the abscissa and the concentration is used as the ordinate. Linear fitting is performed to obtain the working curve of haloacetic acid, as shown in Table 2.

Table 2 Fitting curve of haloacetic acid in drinking water

As can be seen from Table 2, through silane derivatization, the working curves of the seven haloacetic acids all have very good linearity (>0.99), indicating that they can be used for the quantitative analysis of haloacetic acids in actual samples.

(5)Sample analysis

The above steps were used to analyze and determine the contents of 7 haloacetic acids in tap water from 12 households, and the results were obtained. Take the peak area, and then use the working curve correction (internal standard method) to obtain the concentration in drinking water. The specific results are shown in (Table 3).

Table 3 Concentrations of haloacetic acid in tap water of urban households in Suzhou (μg/L).

It can be concluded from Table 3 that haloacetic acids are all present in household drinking water in Suzhou. The average concentrations of dichloroacetic acid, trichloroacetic acid, chlorobromoacetic acid and dibromoacetic acid are all >1 μg/L, with relatively high concentration level. The concentrations of monochloroacetic acid, bromoacetic acid and monoiodoacetic acid are all <1μg/L, especially the concentration of monoiodoacetic acid is lower than 0.1μg/L. Monoiodoacetic acid is currently the most cytotoxic disinfection by-product, and animal experiments have proven that it is carcinogenic. Therefore, the development of disinfection by-products that can detect low concentrations but are highly toxic is of great significance to protecting the safety of drinking water.

(6)Quality control and assurance

In order to examine the reliability of the method, the present invention monitored the recovery rate. Suzhou urban drinking water samples were selected for parallel sample experiments and matrix spiking to determine the precision of the method. In addition, in order to obtain the detection limit of the method, we spiked its ultrapure water (0.1 μg/L) and then analyzed it seven times in parallel. The method detection limit is determined by the following formula:
MDL＝3.1×S (1)

In the formula, MDL is the method detection limit (μg/L), and S is the standard deviation. The specific results are shown in Table 1 and Table 4.

Table 4 Spiked recovery and precision of haloacetic acid in drinking water

As can be seen from Table 4, the standard recovery rate of this method is between 70-130%, and the precision is far less than 30%, which meets the requirements of the analysis method of pollutants in drinking water.

Obviously, the above-mentioned embodiments are only examples for clear explanation and are not intended to limit the implementation. For those of ordinary skill in the art, other changes or modifications may be made based on the above description. An exhaustive list of all implementations is neither necessary nor possible. The obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

A gas chromatography-mass spectrometry method for analyzing haloacetic acid in drinking water, which is characterized by including the following steps:

(1) Take a drinking water sample, add residual chlorine quenching agent for quenching, use an organic solvent to extract haloacetic acid in the drinking water, and prepare a sample solution;

(2) Use haloacetic acid as the standard substance, use organic solvents as the solvent, and prepare a mixed standard solution through gradual dilution;

(3) Use gas chromatography-mass spectrometry to detect and analyze the mixed standard solution and sample solution respectively;

(4) Draw a standard curve and perform sample analysis based on the detection and analysis results in step (3).
The gas chromatography-mass spectrometry analysis method according to claim 1, wherein in step (1), the haloacetic acid in the drinking water is a disinfection by-product obtained by the disinfection process of drinking water.
The gas chromatography-mass spectrometry analysis method according to claim 1, wherein in step (1), the organic solvent is selected from one or more of methyl tert-butyl ether, n-hexane and ethyl acetate. .
The gas chromatography-mass spectrometry analysis method according to claim 1, characterized in that the specific steps of step (1) are: taking a drinking water sample, measuring the residual chlorine in the water, and adding a residual chlorine quenching agent for quenching , adjust the pH to acidic, add the injection internal standard and derivatization reagent to obtain a sample solution.
The gas chromatography-mass spectrometry analysis method according to claim 4, wherein the pH is <1.
The gas chromatography-mass spectrometry analysis method according to claim 4, wherein the derivatization reagent is selected from silanization reagents.
The gas chromatography-mass spectrometry analysis method according to claim 6, wherein the silanization reagent is selected from bis(trimethylsilyl)trifluoroacetamide, N-(tert-butyldimethylsilyl) -One or more of N-methyltrifluoroacetamide, trimethylchlorosilane, hexamethyldisilazane and N,N dimethylformamide.
The gas chromatography-mass spectrometry analysis method according to claim 4, characterized in that the remaining Chlorine quenchers are ascorbic acid and/or ammonium chloride.
The derivatization conditions of the derivatization reagent are: heating temperature 25°C-80°C, reaction time 10min-30min.
The gas chromatography-mass spectrometry analysis method according to claim 1, characterized in that, in step (2), the haloacetic acid is selected from the group consisting of monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, dibromoacetic acid, One or more of monochloromonobromoacetic acid and monoiodoacetic acid.