Method for detecting two chloronaphthylamines in drinking water by gas chromatography-mass spectrometry

Abstract

The invention provides a method for detecting two types of chloronaphthylamine in drinking water by gas chromatography-mass spectrometry, which comprises the following steps: optimizing conditions such as a chromatographic column and temperature programming thereof, an extracting solvent and the use amount thereof, and combining liquid-liquid extraction with a gas chromatography-mass spectrometer to detect two types of chloronaphthylamine in drinking water. The invention establishes a novel method for simultaneously determining the content of two novel nitrogen-containing disinfection byproducts 2-chloro-1-naphthylamine and 4-chloro-1-naphthylamine in drinking water. The method has the characteristics of simplicity, accuracy, good reproducibility, high sensitivity and the like, is suitable for quantitative detection of 2-chloro-1-naphthylamine and 4-chloro-1-naphthylamine in drinking water, and provides a technical means for guaranteeing the quality safety of domestic drinking water.

Description

Technical Field

[0001] The invention belongs to the technical field of water quality detection, and particularly relates to a method for detecting two chloronaphthylamines in drinking water by gas chromatography-mass spectrometry. Background Art

[0002] To control pathogenic microorganisms in raw water, disinfection is an essential step in the tap water production process. Chlorine, due to its high oxidizing properties, readily available, and low cost, has become the primary disinfectant for drinking water in my country, playing a crucial role in ensuring drinking water safety. However, it also produces a series of disinfection byproducts (DBPs). Epidemiological studies have shown that DBPs are not only carcinogenic but may also pose a risk to human reproductive health. To date, while over 700 DBPs have been reported, over 50% of the total organic halogens remain unidentified. These unidentified DBPs are likely potential carcinogens. Therefore, the detection and identification of DBPs is crucial. Disinfection byproducts are generally classified into carbonaceous disinfection byproducts (C-DBPs) and nitrogenous disinfection byproducts (N-DBPs) based on their type. Although carbonaceous disinfection byproducts are more frequently detected in drinking water than nitrogenous disinfection byproducts, nitrogenous disinfection byproducts are more toxic than carbonaceous disinfection byproducts and pose a more serious threat to human health. Consequently, nitrogenous disinfection byproducts have attracted considerable attention in recent years. Common nitrogenous disinfection byproducts include halogenated acetonitrile (HANS), halogenated nitromethanes (HNMs), and N-nitrosodimethylamine (NDMA). For example, N-nitrosodimethylamine has been listed as a reference indicator in the National Standard for Drinking Water Quality (GB5749-2022). With advances in detection technology and improved accuracy, aromatic nitrogenous disinfection byproducts, such as halogenated benzoquinones, halogenated benzoic acids, halogenated phenols and halogenated nitrophenols, and chlorophenylacetonitrile, have been increasingly detected in drinking water. Toxicological studies have shown that the cytotoxicity of aromatic disinfection byproducts is several orders of magnitude higher than that of aliphatic disinfection byproducts. Chloronaphthylamines are a new type of nitrogen-containing aromatic disinfection by-products. The research and detection methods of chloronaphthylamines have never been reported in the literature. Therefore, establishing a detection method for the determination of 2-chloro-1-naphthylamine and 4-chloro-1-naphthylamine is crucial to understand and control the content of these two compounds in drinking water. Summary of the Invention

[0003] Technical Problem to Be Solved: To address the above-mentioned issues, the present invention aims to provide a method for the detection of two chloronaphthylamines in drinking water by gas chromatography-mass spectrometry (GC-MS). By coupling liquid-liquid extraction with gas chromatography-mass spectrometry, a new method for the determination of 2-chloro-1-naphthylamine and 4-chloro-1-naphthylamine in drinking water has been established. This method is simple, accurate, highly sensitive, and reproducible, and is suitable for the quantitative detection of 2-chloro-1-naphthylamine and 4-chloro-1-naphthylamine in drinking water, providing a technical means for ensuring the quality and safety of drinking water.

[0004] Technical solution: A method for detecting two chloronaphthylamines in drinking water by gas chromatography-mass spectrometry, comprising the following steps: S1. Water sampling: Collect water samples, add 0.01-0.02 g / L ascorbic acid to remove chlorine-containing disinfectants, and store in a refrigerated, sealed container. S2. Water sample treatment: Take 100-1000mL of the water sample in S1, add 10-50g of sodium chloride, shake until completely dissolved, add 5-20mL of dichloromethane, shake for 2-5min, transfer to a separatory funnel, let stand and separate, collect the extract, repeat the extraction 2-3 times, and combine the extracts; after dehydrating the extract with anhydrous sodium sulfate, use a concentrator to concentrate to 0.5-2.0mL, then add 1-10μL of internal standard stock solution to obtain the treated water sample for testing; S3. Water sample testing and result judgment: Use gas chromatography-mass spectrometry to measure the treated water samples, and make qualitative and quantitative judgments on whether the water samples contain chlornaphthylamine. Furthermore, the chloronaphthylamines in step S3 are 2-chloro-1-naphthylamine and 4-chloro-1-naphthylamine. Furthermore, the internal standard stock solution in step S2 is a 10 mg / L naphthalene-d8 internal standard stock solution. Furthermore, the preparation steps of the 10 mg / L naphthalene-d8 internal standard stock solution are specifically as follows: take 100 μL of 1000 mg / L naphthalene-d8 into a 10 mL volumetric flask and dilute to the scale with methanol. Furthermore, the gas chromatography conditions in step S3 are: Chromatographic column: capillary column, non-polar column: HP-5MS, 30m×0.25mm×0.25μm or other equivalent columns; Inlet temperature: 230-300℃; Injection volume: 1-5 μL, splitless injection; Flow rate: 1.0 mL / min; Carrier gas: 99.999% high purity helium; Temperature program: hold at 40°C for 2 min, increase to 290°C at a rate of 20°C / min and hold for 6 min. Furthermore, the mass spectrometry conditions in step S3 are: Ion source temperature: 230°C; Quadrupole temperature: 150°C; EI source electron energy: 70eV; Transmission line temperature: 280°C; Acquisition method: ion SIM scan; Internal standard method for quantification and full scan for qualitative analysis; Solvent delay: 6 min; Naphthalene-d8: retention time 8.02 min, qualifier ions 136,108 m / z, quantifier ion 136 m / z; 2-Chloro-1-naphthylamine: retention time 11.37 min, qualifier ion 177,115 m / z, quantifier ion 177 m / z; 4-Chloro-1-naphthylamine: retention time 11.91 min, qualifier ions 177,115 m / z, quantifier ion 177 m / z. Beneficial effects: 1. The present invention establishes a new method for simultaneously determining the contents of two new nitrogen-containing disinfection byproducts (2-chloro-1-naphthylamine and 4-chloro-1-naphthylamine) in drinking water by combining liquid-liquid extraction with gas chromatography-mass spectrometry. The method is simple, accurate, reproducible, and highly sensitive, and is suitable for the quantitative detection of 2-chloro-1-naphthylamine and 4-chloro-1-naphthylamine in drinking water, providing a technical means for ensuring the quality and safety of drinking water. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 The figure is a chromatogram of chloronaphthylamine compounds, wherein peak 1 is naphthalene-d8; peak 2 is 2-chloro-1-naphthylamine; and peak 3 is 4-chloro-1-naphthylamine. Figure 2 This is a comparison chart of the effects of extraction solvents on the recovery rates of two chloronaphthylamines; Figure 3 The figure shows the recovery rate of two chloronaphthylamines as a function of dichloromethane dosage; Figure 4 The figure shows the effect of NaCl content on the recovery of two chloronaphthylamines; Figure 5 Schematic diagram of the standard curve (internal standard method) of 2-chloro-1-naphthylamine; Figure 6 Schematic diagram of the standard curve (internal standard method) of 4-chloro-1-naphthylamine; Figure 7 This is the test result of the water sample from the water plant of the water supply company. Peak 1 is naphthalene-d8; Peak 2 is 2-chloro-1-naphthylamine; Peak 3 is 4-chloro-1-naphthylamine; Figure 8 This is the spectrum of the test results of the water samples at the end of the water plant pipeline of the water supply company. Among them, Peak 1 is naphthalene-d8; Peak 2 is 2-chloro-1-naphthylamine; Peak 3 is 4-chloro-1-naphthylamine. DETAILED DESCRIPTION The present invention will be further described below with reference to the accompanying drawings and embodiments. The following embodiments are intended to explain the present invention, but the present invention is not limited to the following embodiments: Main instruments and reagents Main instruments: Gas chromatograph / mass spectrometer, Agilent 7890B-5977C, oscillator, Tokyo Rika MMV-1000W, concentrator, Labtech MultiVap 8, water purifier, Millipore Milli-Q; Main reagents: 2-chloro-1-naphthylamine and 4-chloro-1-naphthylamine standards, Merck, Germany; naphthalene-d8 1000 mg / L in methanol (internal standard), Beijing Tanmo Quality Inspection Technology Co., Ltd.; dichloromethane, n-hexane, and methanol were all chromatographically pure; sodium chloride and anhydrous sodium sulfate were both analytically pure, Sinopharm Chemical Reagent Co., Ltd. Example 1 A method for detecting two chloronaphthylamines in drinking water by gas chromatography-mass spectrometry comprises the following steps: S1. Water sampling: Collect water samples, add 0.01 g / L ascorbic acid to remove chlorine-containing disinfectants, and store in a refrigerated, sealed container. S2. Water sample treatment: Take 500mL of the water sample in S1, add 20g of sodium chloride, and shake until it is completely dissolved; add 10mL of dichloromethane, shake for 3min, then transfer to a separatory funnel, let stand to separate the layers, collect the extract, repeat the extraction twice, and combine the extracts; dehydrate the extract with anhydrous sodium sulfate, use a concentrator to concentrate to 1mL, and then add 2μL of internal standard stock solution for testing; S3. Water sample testing and result judgment: Use gas chromatography-mass spectrometry to measure the treated water sample, and make qualitative and quantitative judgments on whether the water sample contains chlornaphthylamine. Among them, the gas chromatography conditions are: Chromatographic column: capillary column, non-polar column HP-5MS, 30m×0.25mm×0.25μm; Inlet temperature: 280°C; Injection volume: 1 μL, splitless injection; Flow rate: 1.0 mL / min; Carrier gas: 99.999% high purity helium; Temperature program: maintain at 40°C for 2 min, increase to 290°C at a rate of 20°C / min and maintain for 6 min. Furthermore, the mass spectrometry conditions in step S3 are: Ion source temperature: 230°C; Quadrupole temperature: 150°C; EI source electron energy: 70eV; Transmission line temperature: 280°C; Acquisition method: ion SIM scan; Internal standard method for quantification and full scan for qualitative analysis; Solvent delay: 6 min; Naphthalene-d8: retention time 8.02 min, qualifier ions 136,108 m / z, quantifier ion 136 m / z; 2-Chloro-1-naphthylamine: retention time 11.37 min, qualifier ion 177,115 m / z, quantifier ion 177 m / z; 4-Chloro-1-naphthylamine: retention time 11.91 min, qualifier ions 177,115 m / z, quantifier ion 177 m / z. 1. Selection of chromatographic column and heating program Two common capillary columns of varying polarity, the HP-5MS (30 m × 0.25 mm × 0.25 μm) and the DB-624 (30 m × 0.25 mm × 1.4 μm), were used for the experiment. Both the non-polar HP-5MS and the intermediate-polarity DB-624 capillary columns performed well in separating the two chloronaphthylamines; however, the DB-624 column exhibited a slower peak elution time, so the HP-5MS capillary column was chosen for the experiment. At the same time, the column temperature program also has a great influence on the separation of each component. Finally, after many experiments, it was found that when the program temperature was kept at 40℃ for 2 minutes, and then heated to 290℃ at a rate of 20℃ / min and kept for 6 minutes, naphthalene-d8, 2-chloro-1-naphthylamine and 4-chloro-1-naphthylamine could achieve better separation effect. In summary, the chromatogram of the mixed standard solution is as follows Figure 1 shown. 2. Extraction solvent selection The two chloronaphthylamines (2-chloro-1-naphthylamine and 4-chloro-1-naphthylamine) are both organic compounds and have a certain solubility in organic reagents. Therefore, the extraction efficiency of the two chloronaphthylamines in pure water samples spiked with dichloromethane, ethyl acetate, and n-hexane (spiked at 100 μg / L) was compared. The results are shown in Figure 2. Figure 2 .Depend on Figure 2 It can be seen that using dichloromethane as the extraction solvent, the recovery rates of the two chloronaphthylamines were both above 90%, and its overall recovery rate was higher than that of the other two extraction solvents. Therefore, dichloromethane was selected as the extraction solvent in this experiment. 3. Selection of extraction solvent dosage The amount of extraction solvent used must take into account both the sample volume and environmental hazards of the test. Dichloromethane is a toxic and hazardous reagent. After ensuring that the target compound is almost completely extracted, the amount used should be as small as possible. The literature reports that the principle of small amounts and multiple times can improve the extraction effect. Therefore, this experiment uses two extractions. However, when the amount of extraction solvent used is too small, it is difficult to completely extract the sample, and the recovery rate is difficult to meet the requirements, affecting the accuracy of the results. The experiment examined the effect of dichloromethane at each dosage of 5.0, 10.0, 15.0, and 20.0 mL on the peak area of ​​two chloronaphthylamines. The results are as follows: Figure 3As shown in the figure, as the amount of dichloromethane increases, the recovery rate also gradually increases. When the amount of dichloromethane is 15mL, the recovery rate basically stops increasing. Therefore, considering environmental factors, the experiment finally determined that the amount of dichloromethane sampled each time was 15mL. 4. Salt effect on extraction Adding a certain amount of sodium chloride to the aqueous solution can reduce the solubility of organic matter in water, thereby increasing the extraction amount of the target compound in the extraction solvent. The effect of adding 0, 5, 10, 20, 30, and 50g of NaCl to the chlornaphthylamine aqueous solution on the extraction effect was tested. The results are as follows Figure 4 As shown in the figure, the extraction amount of these two substances gradually increased with the increase of NaCl content. When it reached 20g, the increase was no longer obvious. Therefore, 20g / 500ml sodium chloride solution was selected as the experimental condition. 5. Linear range, regression equation, correlation coefficient and detection limit Weigh 50 mg of each of the 2-chloro-1-naphthylamine and 4-chloro-1-naphthylamine standards, dissolve them in a small amount of methanol, and transfer them to a 50 mL volumetric flask. Then, dilute to the mark with methanol to obtain a 1000 mg / L chloronaphthylamine mixed standard stock solution. Pipette 200 μL of the 1000 mg / L chloronaphthylamine mixed standard stock solution into a 20 mL volumetric flask and dilute to the mark with methanol to obtain a 10.0 mg / L chloronaphthylamine mixed standard solution. Transfer 100 μL of 1000 mg / L naphthalene-d8 to a 10 mL volumetric flask and dilute to the mark with methanol to obtain a 10.0 mg / L naphthalene-d8 internal standard stock solution. Get different volumes of 10.0mg / L chloronaphthylamine mixed standard solution and certain volume of 10.0mg / L naphthalene-d8 internal standard stock solution, dilute with methanol, be made into 0.00,5.00,10.0,20.0,50.0,100,150,200,500 μ g / L serial concentration, and making internal standard content is 20.0 μ g / L, put into gas chromatograph mass spectrometer sample tray then, analyze according to instrument operating condition among the embodiment 1. The results showed that the linear range of the two chloronaphthylamine methods was 5.00-500 μg / L, and the correlation coefficients (r) were all above 0.9990. According to the provisions of 6.4 of the "Standard Test Methods for Drinking Water Part 3: Water Quality Analysis Quality Control" (GB / T 5750.3-2023), the method detection limit (MDL) was calculated with a signal-to-noise ratio (S / N) of 3 for the chromatographic method, and the quantification limit (MQL) was set at 3 times the detection limit in 6.5. At the same time, based on a sample volume of 500 mL, the method MDL was 0.0033 μg / L and the MQL was 0.010 μg / L. The linear ranges, regression equations, correlation coefficients, and detection limits of the two compounds are shown in Table 1, and the standard curves are shown in Table 1. Figure 5 and Figure 6shown. Table 1 Linear range, detection limit, linear equation and correlation coefficient Compound Linear range (μg / L) Regression equation Correlation coefficient Method detection limit (μg / L) 2-Chloro-1-naphthylamine 5.00～500 y=0.4530x+0.0417 0.9996 0.0033 4-Chloro-1-naphthylamine 5.00～500 y=0.3737x+0.0372 0.9995 0.0033 6. Spike recovery and precision test Pure water and drinking water were spiked with two chlornaphthylamines at high, medium, and low concentrations, respectively. Six replicates were performed according to the experimental method to conduct spike recovery and precision tests. The results are shown in Table 2. The spiked recoveries for pure water ranged from 92.2% to 106%, with relative standard deviations of 3.4% to 6.7%. The spiked recoveries for drinking water ranged from 92.8% to 98.2%, with relative standard deviations of 3.1% to 6.8%. Table 2 Recovery and precision test of two chloronaphthylamines 7. Actual water sample analysis This method was used to determine two chloronaphthylamines in drinking water. Water samples were taken from the water plant of a water supply company and the terminal sampling point of the pipe network. The sample determination was carried out according to the method and detection conditions in Example 1. The results showed that Figure 7 and Figure 8 As shown, the water discharged from a water supply company's water plant ( Figure 7 ) and pipe network terminal water ( Figure 8 ) were not detected in either compound. The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any person skilled in the art can, without departing from the spirit and technical solution of the present invention, use the methods and technical contents disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for detecting two chloronaphthylamines in drinking water by gas chromatography-mass spectrometry, characterized in that: The following steps are involved: S1. Water sample collection: Collect water samples, add 0.01-0.02 g / L ascorbic acid to remove chlorine-containing disinfectants, and store in a refrigerated and sealed container; S2. Water sample treatment: Take 100-1000mL of the water sample in S1, add 10-50g of sodium chloride, shake until completely dissolved, add 5-20mL of dichloromethane, shake for 2-5min, transfer to a separatory funnel, let stand to separate, collect the extract, repeat the extraction 2-3 times, and combine the extracts; dehydrate the extract with anhydrous sodium sulfate, concentrate it to 0.5-2.0mL using a concentrator, and then add 1-10μL of internal standard stock solution to obtain the treated water sample for testing; S3. Water sample testing and result judgment: Use gas chromatography-mass spectrometry to measure the treated water samples, and make qualitative and quantitative judgments on whether the water samples contain the two types of chloronaphthylamines.

2. The method for detecting two kinds of chloronaphthylamines in drinking water by gas chromatography-mass spectrometry according to claim 1, characterized in that: The chloronaphthylamines are 2-chloro-1-naphthylamine and 4-chloro-1-naphthylamine.

3. The method for detecting two kinds of chloronaphthylamines in drinking water by gas chromatography-mass spectrometry according to claim 1, characterized in that: The internal standard stock solution in step S2 is a 10 mg / L naphthalene-d8 internal standard stock solution.

4. The method for detecting two kinds of chloronaphthylamines in drinking water by gas chromatography-mass spectrometry according to claim 3, characterized in that: The preparation steps of the 10 mg / L naphthalene-d8 internal standard stock solution are as follows: take 100 μL of 1000 mg / L naphthalene-d8 into a 10 mL volumetric flask, and dilute to the mark with methanol.

5. The method for detecting two chloronaphthylamines in drinking water by gas chromatography-mass spectrometry according to claim 1, characterized in that: The gas chromatography conditions in step S3 are: Chromatographic column: capillary column, non-polar column: HP-5MS, 30m×0.25mm×0.25μm or other equivalent columns; Inlet temperature: 230-300℃; Injection volume: 1-5 μL, splitless injection; Flow rate: 1.0 mL / min; Carrier gas: 99.999% high purity helium; Temperature program: maintain at 40°C for 2 min, increase the temperature to 290°C at a rate of 20°C / min and maintain for 6 min.

6. The method for detecting two chloronaphthylamines in drinking water by gas chromatography-mass spectrometry according to claim 1, characterized in that: The mass spectrometry conditions in step S3 are: Ion source temperature: 230°C; Quadrupole temperature: 150°C; EI source electron energy: 70eV; Transmission line temperature: 280°C; Acquisition method: ion SIM scanning; Internal standard method for quantification and full scan for qualitative analysis; Solvent delay: 6min; Naphthalene-d8: retention time 8.02min, qualifier ion 136,108m / z, quantifier ion 136m / z; 2-Chloro-1-naphthylamine: retention time 11.37 min, qualifier ion 177,115 m / z, quantifier ion 177 m / z; 4-Chloro-1-naphthylamine: retention time is 11.91min, qualifier ion is 177,115m / z, and quantitative ion is 177m / z.

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