CN111679007A - A method for simultaneous detection of 13 halogenated amide disinfection by-products in drinking water - Google Patents

Abstract

The invention relates to a method for simultaneously detecting 13 kinds of halogenated amides (HAcAms) disinfection by-products in drinking water, and belongs to the field of analytical chemistry. The purpose is to provide a method for the simultaneous determination of 13 halogenated amides in drinking water without enriching and concentrating the samples, so as to improve the analysis efficiency and avoid the use of organic solvents in the pretreatment process and their health effects on operators. The method uses high-performance liquid chromatography-tandem mass spectrometer for determination, and the detailed instrument parameters are determined. It only takes 10 minutes to detect a sample, and the automatic sampler is used for sample injection, which can realize high-throughput and accurate quantification of the sample. The method The standard addition recovery rate and detection sensitivity are high, and the concentration detection of ng/L level can be achieved by direct injection, which will facilitate the development of HAcAms monitoring in drinking water.

Description

A method for simultaneous detection of 13 halogenated amide disinfection by-products in drinking water

technical field

The invention belongs to the field of hygiene detection, relates to water quality detection and analysis technology, and in particular relates to a method for simultaneously detecting 13 kinds of halogenated amide disinfection by-products in drinking water by using a high performance liquid chromatography-tandem mass spectrometer;

Background technique

Drinking water disinfection has been widely promoted because it can effectively control water-borne infectious diseases caused by pathogenic microorganisms in water bodies, and has also become one of the most important technological advances in the field of public health in the 20th century; however, drinking water disinfection is also like a "double "Blade sword", which kills pathogenic microorganisms in water, but also brings the health hazards of disinfection by-products in drinking water;

In 1974, Rook and Beller et al discovered the disinfection by-products of trihalomethanes (THMs) represented by chloroform (CHCl ₃ ) in chlorinated drinking water for the first time; in 1976, the United States Environmental Protection Agency (USEPA) carried out The results of a national survey of THMs showed the prevalence of THMs in chlorinated drinking water; in the same year, a National Cancer Institute (NCI) study reported that _CHCl3 can cause renal tubular adenocarcinoma in male rats and hepatocytes in female mice. cancer; followed by Salmonella typhimurium reverse mutation assay (Ames) results showed that drinking water organic extracts are mutagenic; these series of research results have drawn great attention to the major public health problem of drinking water disinfection by-products ; In order to reduce the health risks brought by disinfection by-products to people as much as possible, China, the United States, Japan, the World Health Organization (WHO), the European Union (EU) and other countries and organizations have successively put THMs, halogenated Disinfection by-products such as acetic acid (HAAs), bromate, chlorate, and chlorite are included in their drinking water-related standards and the corresponding standard limits are formulated; however, the type and content of disinfection by-products in drinking water are affected by disinfection. The types of disinfectants used in the process and the pollution status of water sources vary. With the rapid development of detection technology, more than 700 DBPs were found in drinking water and disinfection simulation experiments; the United States carried out a large-scale A survey on the pollution status of drinking water disinfection by-products in China, conducted a systematic survey of more than 70 emerging disinfection by-products, including halogenated acetonitriles (HANs), halogenated nitromethanes (HNMs) and other nitrogen-containing disinfection by-products, and conducted a systematic survey for the first time. Disinfection by-products of halogenated amides (HAcAms) were discovered;

HAcAms refers to a class of substances in which the hydrogen on acetamide is replaced by halogen, and the hydrogen on the carbon atom directly connected to the acetyl group is replaced by chlorine, bromine and iodine to form monohaloamide, dihaloamide and trihalide. Halogenated amides; there are 13 kinds of HAcAms reported so far, and their chemical structures and basic information are shown in Figure 1 and Table 1; relevant toxicity research data show that the toxicity of HAcAms is significantly higher than that of conventional drinking water-related standards such as THMs and HAAs. Disinfection by-products; researchers from the United States, Australia, Japan, the United Kingdom and other countries have investigated HAcAms pollution in drinking water in some areas, and some HAcAms have been detected, and the maximum total concentration is (3.80-8.18) μg/L; Shenzhen residents in China drink The concentration range of some HAcAms in water is (0.1-3.1) μg/L. However, due to the detection limit of existing detection methods, the pollution of HAcAms in drinking water still lacks a systematic understanding; The binding between them is very strong, although their molecular weight is low, they are not volatile, and are prone to hydrolysis under acidic and alkaline conditions. Therefore, these unique properties bring greater detection of HAcAms in drinking water. At present, the reported detection methods mainly include gas chromatography (GC-ECD), gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), etc. It is necessary to combine liquid-liquid extraction (LLE), solid-phase extraction (SPE), acid-catalyzed hydrolysis, and silanization and other pre-treatments; on the one hand, these pre-treatments are complicated and require a lot of manpower, material resources and time. On the other hand, the above-mentioned pre-treatments The process cannot achieve 100% recovery of HAcAms in drinking water samples, and HAcAms may be hydrolyzed during this process, making it difficult to detect halogenated amides in drinking water or the detection concentration is low; in addition, the sensitivity of these methods It is also unable to meet the detection needs of lower concentrations of HAcAms in drinking water; the above limitations of the existing detection methods limit the development of HAcAms monitoring in drinking water; Figure 1 and Table 1:

Table 1 Basic information of 13 HAcAms

Chinese patent CN106596751A discloses a high performance liquid chromatography/electrospray mass spectrometry detection method of chlorinated disinfection by-products dichloroacetamide and trichloroacetamide, CN105866287A and CN106338559B disclose a gas phase detection method of chlorine disinfection by-product dichloroacetamide Chromatographic detection methods, the above two methods have the advantages of simplicity, high efficiency, high sensitivity, wide linear range, good reproducibility, high recovery rate, accurate instrumental analysis results, and clear spectral analysis, but they can only detect dichloroethane at the same time. Two HAcAms, amide and trichloroacetamide, or the detection of dichloroacetamide alone cannot achieve the simultaneous detection of 13 HAcAms; and these two methods also require solid-phase extraction or liquid-liquid extraction for sample concentration and enrichment;

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for simultaneously detecting 13 kinds of halogenated amide disinfection by-products in drinking water, so as to overcome the deficiencies in the existing methods such as sample pretreatment, recovery rate, sensitivity, etc., without the need for enrichment and concentration. The high-throughput detection of HAcAms in drinking water as low as ng/L concentration can be achieved by direct injection, and the positive and negative switching can be performed quickly without loss of sensitivity. After simple centrifugation to remove impurities, the sample can be injected to ensure the accuracy of the results;

The object of the present invention can be realized through the following technical solutions:

1. Operating parameters of high performance liquid chromatography-tandem mass spectrometer

1. Chromatographic conditions

The chromatographic column is HSS T3, 2.5μm, 2.1×150mm; the mobile phase includes mobile phase A and mobile phase B: mobile phase A is 0.1% acetic acid water, mobile phase B is acetonitrile, 0.4mL/min; gradient elution: mobile phase Phase A+mobile phase B=100%; 0～7min, the volume percentage of mobile phase A decreases from 95% to 60%; 7～8min, the volume percentage of mobile phase A keeps at 60%; 8.1～10min, the volume percentage of mobile phase A keeps at 95% %; the column temperature is 40min°C; the injection volume is 50μL; the flow rate is 0.4mL/min;

2. Mass spectrometry conditions

ESI source, mass spectrometry multiple reaction monitoring mode (MRM), Curtain Gas (CUR) 30psi, Collision Gas medium, Ion Spray Voltage (IS) 5500/-4500V, ion source temperature (Temperature Gas) , TEM) 400 ℃, atomizing gas (Nebulizer Gas, GS1) 55psi, drying gas (Heater Gas, GS2) 55psi;

The manufacturer of the triple quadrupole mass spectrometer is AB SCIEX, and the model is Qtrap ⁶⁵⁰⁰⁺ ;

3. Determine the mass spectrometry parameters of 13 HAcAms

The 13 HAcAms and their mass spectrometry parameters are shown in Table 2

Table 2

2. Sample testing and analysis

1. Draw the standard curve of 13 HAcAms

(1) Prepare standard solution

The 13 HAcAms are commercially available products, among which CAcAm (≥98.0%), BAcAm (98%), IAcAm (≥99.0%), TCAcAm (99.0%) were purchased from Sigma-Aldrich Company in the United States, BCAcAm (99+%) , BDCAcAm(99+%), TBAcAm(99+%), CIAcAm(99+%), DBCAcAm(99+%), DBAcAm(99+%), DIAcAm(99+%) and BIAcAm(85+%) From Canada CanSyn Chem Company, DCAcAm (98+%) was purchased from Shanghai Bailingwei Company (J&K Chemical Ltd.); appropriate amounts of 13 HAcAms standard products were weighed and prepared into single standard stock solutions with a concentration of 1000 mg/L in methanol; After mixing 50 μl of each of the 13 HAcAms single standard stock solutions, the volume was adjusted to 5 ml with ultrapure water to obtain a mixed standard stock solution with a concentration of 10 mg/L, which was diluted with ultrapure water to obtain a mixture of HAcAms with a concentration of 1 mg/L before use. Standard use solution; then draw a certain volume of mixed standard and dilute with ultrapure water to obtain concentrations of 0.001μg/L, 0.005μg/L, 0.010μg/L, 0.025μg/L, 0.050μg/L, 0.100μg/L, respectively. L, 0.200 μg/L, 0.300 μg/L, 0.500 μg/L, 1.00 μg/L, 5.00 μg/L, 10.0 μg/L, 100 μg/L of standard series solutions, the standard stock solutions were stored in the brown volume In a bottle, store it in the refrigerator at 4°C away from light;

(2) Use high performance liquid chromatography-tandem mass spectrometer to analyze standard solutions of different concentrations, and measure according to the parameters determined in step 1 to obtain chromatograms of 13 kinds of HAcAms in the standard solution; obtain each HAcAms in the standard solution from the chromatogram. The retention time of each kind of HAcAm, the area of the quantitative ion pair, the area of the qualitative ion pair; take the area of each kind of HAcAm quantitative ion pair in the standard solution as the ordinate, and take the concentration of each kind of HAcAm in the standard solution as the abscissa, get 13 Standard curve of various HAcAms standards;

2. Take 10 mL of drinking water sample and centrifuge it at 10,000 rpm for 5 minutes, then take 1 mL and put it in a sample bottle, inject it into the high performance liquid chromatography-tandem mass spectrometer through the automatic injector of the high performance liquid chromatography-tandem mass spectrometer, and follow step 1. The determined parameters are measured to obtain the chromatogram of the drinking water sample;

3. Obtain the retention time, quantitative ion pair area, and qualitative ion pair area of each HAcAm in the drinking water sample from the chromatogram of the drinking water sample obtained in step 2; The area ratio of the qualitative ion pair to the quantitative ion pair was compared with the retention time of each HAcAm in the standard solution obtained in step 2-1-(2), and the area ratio of the qualitative ion pair to the quantitative ion pair. 13 kinds of HAcAms were qualitatively analyzed, and the drinking water samples were quantitatively analyzed according to the standard curve of 13 kinds of HAcAms standard products obtained in step 2-1-(2), and the contents of 13 kinds of HAcAms in the drinking water samples were obtained.

The present invention has the following beneficial effects:

1. The method of the present invention adopts direct sample injection, which avoids the complicated sample pretreatment process, reduces the loss of HAcAms in the sample, and avoids the use of organic solvents in the pretreatment process and its impact on the health of operators;

2. The present invention adopts high-performance liquid chromatography-tandem mass spectrometer for determination, and it only takes 10 minutes to detect a sample, which can achieve high-throughput accurate quantification of the sample, high detection sensitivity, and can reach ng/L level without enrichment and concentration. The method has strong anti-pollution ability. The drinking water sample can be injected by simply taking the supernatant by high-speed centrifugation; the detection sensitivity is represented by the detection limit, and the detection limit of 13 kinds of HAcAms in the method of the present invention It is 0.001-0.1μg/L; the standard curve has a good linear relationship, and the correlation coefficients are all greater than 0.995; ultrapure water is used as the blank background for standard addition and recovery experiments, 0.5μg/L, 1.0μg/L and 5.0μg/L 3 concentrations The recovery rate of standard addition is 70%-120%;

3. The present invention can simultaneously measure 13 kinds of HAcAms in drinking water, and on the basis of the existing method, the complicated sample pretreatment process is eliminated, the detection range of only one to two kinds of HAcAms can be expanded, and the analysis efficiency is significantly improved;

4. The present invention adopts an automatic sampler for sample injection, which does not require personnel to be on duty, and can automatically complete the determination of large batches of samples.

Description of drawings

Figure 1 Chemical structures of 13 HAcAms,

Figure 2 Chromatograms of 13 HAcAms,

Figure 3 Chloroacetamide: y=2.12117e5x+12846.77511 (r2=0.994),

Figure 4 bromoacetamide y=4.19577e5x+-788.51358 (r2=0.993),

Figure 5-Chloro-bromoacetamide y=4.12422e5x+1474.15556 (r2=0.997),

Figure 6 Iodoacetamide y=1.10107e6x+263.67969 (r2=0.997),

Figure 7 Dibromoacetamide y=3.51105e4x+1523.31214 (r2=0.994),

Figure 8-chloro-iodoacetamide y=1.36186e6x+21061.58208 (r2=0.997),

Figure 9-bromo-iodoacetamide y=7.96555e5x+-3115.58268 (r2=0.999),

Figure 10 Tribromoacetamide y=9.46847e4x+18521.80758 (r2=0.994),

Figure 11 Diiodoacetamide y=2.83739e6x+9719.94511 (r2=0.998),

Figure 12 Dichloroacetamide: y=3.48758e4x+7637.32717 (r2=0.994),

Figure 13 Trichloroacetamide y=4.11098e4x+5601.84904 (r2=0.999),

Figure 14 Dichloromonobromoacetamide y=16334.32286x+793.18113 (r2=0.997),

Figure 15 Monochlorodibromoacetamide y=20137.13833x+398.01775 (r2=0.994).

specific embodiment

Adopt the following examples to verify the beneficial effects of the present invention:

Example 1:

The present embodiment detects factory water and peripheral water; the present embodiment adopts high performance liquid chromatography-tandem mass spectrometer to simultaneously detect 13 kinds of halogenated amide disinfection by-products in drinking water according to the following steps:

1. Operating parameters of high performance liquid chromatography-tandem mass spectrometer

1. Chromatographic conditions

The chromatographic column is HSS T3, 2.5μm, 2.1×150mm; the mobile phase includes mobile phase A and mobile phase B: mobile phase A is 0.1% acetic acid water, mobile phase B is acetonitrile, 0.4mL/min; gradient elution: mobile phase Phase A+mobile phase B=100%; 0～7min, the volume percentage of mobile phase A decreases from 95% to 60%; 7～8min, the volume percentage of mobile phase A keeps at 60%; 8.1～10min, the volume percentage of mobile phase A keeps at 95% %; the column temperature is 40min°C; the injection volume is 50μL; the flow rate is 0.4mL/min;

2. Mass spectrometry conditions

ESI source, mass spectrometry multiple reaction monitoring mode (MRM), Curtain Gas (CUR) 30psi, Collision Gas medium, Ion Spray Voltage (IS) 5500/-4500V, ion source temperature (Temperature Gas) , TEM) 400 ℃, atomizing gas (Nebulizer Gas, GS1) 55psi, drying gas (Heater Gas, GS2) 55psi;

The manufacturer of the triple quadrupole mass spectrometer is AB SCIEX, and the model is Qtrap ⁶⁵⁰⁰⁺ ;

3. Determine the mass spectrometry parameters of 13 HAcAms

The 13 HAcAms and their mass spectrometry parameters are shown in Table 3;

Table 3 Mass spectrometry parameters of 13 halogenated amides

2. Sample testing and analysis

1. Draw the standard curve of 13 HAcAms

(1) Prepare standard solution

The 13 HAcAms are commercially available products, among which CAcAm (≥98.0%), BAcAm (98%), IAcAm (≥99.0%), TCAcAm (99.0%) were purchased from Sigma-Aldrich Company in the United States, BCAcAm (99+%) , BDCAcAm(99+%), TBAcAm(99+%), CIAcAm(99+%), DBCAcAm(99+%), DBAcAm(99+%), DIAcAm(99+%) and BIAcAm(85+%) From Canada CanSyn Chem Company, DCAcAm (98+%) was purchased from Shanghai Bailingwei Company (J&K Chemical Ltd.); appropriate amounts of 13 HAcAms standard products were weighed and prepared into single standard stock solutions with a concentration of 1000 mg/L in methanol; After mixing 50 μl of each of the 13 HAcAms single standard stock solutions, the volume was adjusted to 5 ml with ultrapure water to obtain a mixed standard stock solution with a concentration of 10 mg/L, which was diluted with ultrapure water to obtain a mixture of HAcAms with a concentration of 1 mg/L before use. Standard use solution; then draw a certain volume of mixed standard and dilute with ultrapure water to obtain concentrations of 0.001μg/L, 0.005μg/L, 0.010μg/L, 0.025μg/L, 0.050μg/L, 0.100μg, respectively /L, 0.200μg/L, 0.300μg/L, 0.500μg/L, 1.00μg/L, 5.00μg/L, 10.0μg/L, 100μg/L standard series solutions, the standard stock solutions were stored in brown Store in a volumetric flask and store in a refrigerator at 4°C away from light;

(2) Use high performance liquid chromatography-tandem mass spectrometer to analyze standard solutions of different concentrations, and measure according to the parameters determined in step 1, to obtain chromatograms of 13 kinds of HAcAms in the standard solution (as shown in Figure 2); In the figure, the retention time of each HAcAm in the standard solution, the area of the quantitative ion pair, and the area of the qualitative ion pair are obtained; take the area of each HAcAm quantitative ion pair in the standard solution as the ordinate, and take the area of each HAcAm in the standard solution as the ordinate. The concentration is the abscissa, and the standard curve of 13 HAcAms standards was obtained;

Taking the concentration of each HAcAm in the standard solution as the abscissa, the standard curves of 13 HAcAms standard products were obtained; the standard curves of 13 HAcAms standard products are shown in Figure 3-15:

(3) Method detection limit

The detection limits of 13 HAcAms are shown in Table 3;

Table 3 Detection limits of 13 HAcAms

HAcAms Detection limit concentration (μg/L) HAcAms Detection limit concentration (μg/L) Chloroacetamide 0.001 Monochloro-iodoacetamide 0.005 Dichloroacetamide 0.005 Bromo-iodoacetamide 0.010 Bromoacetamide 0.050 Tribromoacetamide 0.100 Trichloroacetamide 0.100 Diiodoacetamide 0.001 Monochloro-bromoacetamide 0.050 Dichloromonobromoacetamide 0.100 iodoacetamide 0.005 Chlorodibromoacetamide 0.050 Dibromoacetamide 0.100

(4) Recycling by marking

Take ultrapure water as the blank background, add a certain volume of mixed standard solution, and prepare water samples with concentrations of 0.50, 1.00 and 5.00 μg/L, and investigate the reliability of the method. The results are shown in Table 4;

Table 4 The recovery of 13 HAcAms spiked

The standard curves of the 13 kinds of HAcAms obtained in this example have good linearity (r>0.995), the detection limit can be as low as 1 ng/L, the recovery rate is between 70% and 120%, and the accuracy of the detection results is high;

2. Take 10 mL of drinking water sample and centrifuge it at 10,000 rpm for 5 minutes, then take 1 mL and put it in a sample bottle, inject it into the high performance liquid chromatography-tandem mass spectrometer through the automatic injector of the high performance liquid chromatography-tandem mass spectrometer, and follow step 1. The determined parameters are measured to obtain the chromatogram of the drinking water sample;

3. Obtain the retention time, quantitative ion pair area, and qualitative ion pair area of each HAcAm in the drinking water sample from the chromatogram of the drinking water sample obtained in step 2; The area ratio of the qualitative ion pair to the quantitative ion pair was compared with the retention time of each HAcAm in the standard solution obtained in step 2-1-(2), and the area ratio of the qualitative ion pair to the quantitative ion pair. 13 kinds of HAcAms were qualitatively analyzed, and 13 kinds of HAcAms in drinking water samples were quantitatively analyzed according to the standard curve of 13 kinds of HAcAms standard products obtained in step 2-1-(2), and the contents of 13 kinds of HAcAms in drinking water samples were obtained;

The detection results of the present embodiment are shown in Table 5;

Table 5 Detection results of 13 HAcAms in drinking water samples (μg/L)

Claims (1)

1. a method for simultaneously detecting 13 kinds of halogenated amides disinfection by-products in drinking water, is characterized in that, may further comprise the steps: 1) High performance liquid chromatography-tandem mass spectrometer operating parameters, 1. Chromatographic Conditions The chromatographic column is HSS T3, 2.5μm, 2.1×150mm; the mobile phase includes mobile phase A and mobile phase B: mobile phase A is 0.1% acetic acid water, mobile phase B is acetonitrile, 0.4mL/min; gradient elution: mobile phase Phase A+mobile phase B=100%; 0～7min, the volume percentage of mobile phase A decreases from 95% to 60%; 7～8min, the volume percentage of mobile phase A keeps at 60%; 8.1～10min, the volume percentage of mobile phase A keeps at 95% %; the column temperature is 40min°C; the injection volume is 50μL; the flow rate is 0.4mL/min; 2. Mass Spectrometry Conditions ESI source, mass spectrometry multiple reaction monitoring mode, curtain gas 30psi, collision gas medium, ion spray voltage 5500/-4500V, ion source temperature 400°C, atomizing gas 55psi, drying gas 55psi; production of the triple quadrupole mass spectrometer The manufacturer is AB SCIEX, the model is Qtrap ⁶⁵⁰⁰⁺ ; 3. According to the table below, determine the mass spectrometry parameters of 13 HAcAms,

2) Sample detection and analysis 1. Draw the standard curve of 13 HAcAms (1) Prepare standard solution The 13 kinds of HAcAms are commercially available products, among which CAcAm≥98.0%, BAcAm 98%, IAcAm≥99.0%, TCAcAm 99.0% were purchased from Sigma-Aldrich Company in the United States, BCAcAm 99+%, BDCAcAm 99+%, TBAcAm 99+% , CIAcAm 99+%, DBCAcAm 99+%, DBAcAm 99+%, DIAcAm 99+% and BIAcAm 85+%, DCAcAm 98+%; respectively weigh appropriate amounts of 13 HAcAms standards, and prepare them with methanol to prepare a single concentration of 1000mg/L. standard stock solution; take 50 μl of each of the 13 HAcAms single standard stock solutions and mix them with ultrapure water to 5ml to obtain a mixed standard stock solution with a concentration of 10mg/L, which is diluted with ultrapure water before use to obtain a concentration of 1mg/L HAcAms mixed standard solution; then draw a certain volume of mixed standard and dilute with ultrapure water to obtain concentrations of 0.001μg/L, 0.005μg/L, 0.010μg/L, 0.025μg/L, 0.050μg, respectively /L, 0.100μg/L, 0.200μg/L, 0.300μg/L, 0.500μg/L, 1.00μg/L, 5.00μg/L, 10.0μg/L, 100μg/L standard series solutions, the standard The stock solution was stored in a brown volumetric flask and stored in the refrigerator at 4°C protected from light; (2) Use high performance liquid chromatography-tandem mass spectrometer to analyze standard solutions of different concentrations, and measure according to the parameters determined in step 1 to obtain chromatograms of 13 kinds of HAcAms in the standard solution; obtain each HAcAms in the standard solution from the chromatogram. The retention time of each kind of HAcAm, the area of the quantitative ion pair, the area of the qualitative ion pair; take the area of each kind of HAcAm quantitative ion pair in the standard solution as the ordinate, and take the concentration of each kind of HAcAm in the standard solution as the abscissa, get 13 Standard curve of various HAcAms standards; 2. Take 10 mL of drinking water sample and centrifuge it at 10,000 rpm for 5 min, take 1 mL and place it in a sample bottle, inject it into the high-performance liquid chromatography-tandem mass spectrometer through the automatic injector of the high-performance liquid chromatography-tandem mass spectrometer, and follow step 1. The determined parameters are measured to obtain the chromatogram of the drinking water sample; 3. Obtain the retention time, quantitative ion pair area, and qualitative ion pair area of each HAcAm in the drinking water sample from the chromatogram of the drinking water sample obtained in step 2; The area ratio of the qualitative ion pair to the quantitative ion pair was compared with the retention time of each HAcAm in the standard solution obtained in step 2)-1-(2), and the area ratio of the qualitative ion pair to the quantitative ion pair. Qualitative analysis of 13 kinds of HAcAms in drinking water samples was carried out according to the standard curve of 13 kinds of HAcAms standard products obtained in step 2)-1-(2), and the contents of 13 kinds of HAcAms in drinking water samples were obtained.

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