CN111239277B - Method and kit for determining N-dimethyl nitrosamine in water and application - Google Patents

Method and kit for determining N-dimethyl nitrosamine in water and application Download PDF

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CN111239277B
CN111239277B CN202010078856.6A CN202010078856A CN111239277B CN 111239277 B CN111239277 B CN 111239277B CN 202010078856 A CN202010078856 A CN 202010078856A CN 111239277 B CN111239277 B CN 111239277B
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dimethyl nitrosamine
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金米聪
周健
陈晓红
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Ningbo Municipal Center For Disease Control & Prevention
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Abstract

The invention discloses a method for measuring N-dimethyl nitrosamine in water, which is based on the principle of dispersed solid phase extraction, coconut shell activated carbon powder is mixed with a water sample, then ultrasonic-assisted dispersion is carried out to complete extraction, and after the extraction is finished, negative pressure rapid suction filtration and elution are carried out. And then, acidic ionic liquid is added during rotary evaporation, so that volatilization and loss of the N-dimethyl nitrosamine in the rotary evaporation process can be reduced. Compared with the traditional solid phase extraction method, the method greatly shortens the time required by analysis on the premise of ensuring the detection sensitivity and the result reliability. Meanwhile, the invention also provides a corresponding on-site sampling kit which can realize on-site sampling, processing and storage of a water sample by matching with a suction filter and a small-sized ultrasonic instrument, and detection can be realized only by bringing the pretreated sample liquid back to a laboratory for concentration.

Description

Method and kit for determining N-dimethyl nitrosamine in water and application
Technical Field
The invention relates to an analysis detection method, in particular to a detection method of liquid chromatography-tandem mass spectrometry, and specifically relates to a method, a kit and application for determining N-dimethyl nitrosamine in water.
Background
N-Nitrosodimethyl Nitrosamines (NDMA) are a strong polar (log K) with a small molecular weight (74.08g/mol)ow═ 0.57) compound, readily soluble in polar solvents such as water, alcohols and dichloromethane. NDMA in domestic drinking water is mainly derived from chlorination (free chlorine or chloramine) disinfection. NDMA has strong genotoxicity, and the parts which can induce tumor generation mainly generate tumor in esophagus and liver, and also can generate tumor in bladder, brain and lung. The international center for cancer research has assigned carcinogenicity as a grade of 2A due to its carcinogenic risk (95.71X 10)-6) Is significantly greater than trihalomethane (5.32X 10)-6) And haloacetic acid (67.55X 10)-6). At present, the limit value of NDMA is not specified in the current domestic drinking water sanitary standard GB 5749-Developed countries and regions have imposed severe restrictions on them. The world health organization set the NDMA limit to 100ng/L in 2008 based on the japanese scholars research results and canadian drinking water guidelines; the Australian government limits the NDMA content to less than 10ng/L in the same year water circulation guidelines; the NDMA limit in the 2010 drinking water quality guideline in canada was set to 40ng/L, while the environmental department of ontario limited the maximum allowable concentration to below 9 ng/L.
The NDMA detection of the ng/L concentration level in a water sample is realized, and extremely high requirements are imposed on an analysis system. Currently, the detection of NDMA mainly comprises a GC method, an HPLC method, a GC-MS/MS method, an LC-MS/MS method and the like. Although GC-MS/MS is adopted more, LC-MS/MS shows unique superiority when analyzing substances with strong polarity and poor thermal stability, and has higher instrument sensitivity and stronger matrix interference resistance.
The pretreatment method for NDMA detection in drinking water mainly comprises the following steps: liquid-liquid extraction, solid-phase micro-extraction and the like. The liquid-liquid extraction mainly uses dichloromethane for extraction, and because NDMA has stronger polarity and high distribution ratio in water, the method has low extraction efficiency and large organic reagent dosage, and limits the popularization and application thereof. On the other hand, solid-phase extraction is the most common method for enriching trace NDMA in a water sample at present, common solid-phase adsorption materials comprise coconut shell activated carbon, neutral activated carbon and the like, the method is good in stability and high in enrichment times, but the time required by large-volume water samples is long, and the adsorption efficiency is low. The solid phase micro-extraction technology is convenient to operate, does not need an extraction solvent, and is limited by factors such as the type of an extraction head material and the properties of a target object, so that the stability of the result is poor, and the application range is limited.
The invention is based on the principle of dispersive solid-phase extraction, coconut shell activated carbon powder is mixed with a water sample, then ultrasonic-assisted dispersive extraction is carried out, and after the ultrasonic-assisted dispersive extraction is finished, negative pressure rapid suction filtration and elution are carried out. Compared with the traditional solid phase extraction method, the method can greatly shorten the time required by analysis on the premise of ensuring the detection sensitivity and the result reliability.
Disclosure of Invention
The invention adopts ultrasonic-assisted dispersed solid phase extraction, and after the extraction is finished, the negative pressure rapid suction filtration and elution are carried out, and the acidic ionic liquid is added, so that the volatilization loss of NDMA in the rotary evaporation process is reduced. Compared with the traditional solid phase extraction method, the method can greatly shorten the time required by analysis on the premise of ensuring the detection sensitivity and the result reliability.
In order to achieve the purpose of the invention, the invention adopts the technical scheme that: a method for measuring N-dimethyl nitrosamine in water is characterized by comprising the following steps:
(1) pre-activating the solid-phase extraction filler;
(2) adding sodium thiosulfate and an isotope internal standard working solution into a water sample to be detected to obtain a detection solution;
(3) mixing the solution to be detected obtained in the step (2) with the solid-phase extraction filler in the step (1) for ultrasonic dispersion extraction;
(4) carrying out suction filtration on the suspension mixed solution obtained in the step (3) to obtain a filter cake;
(5) pumping the filter cake obtained in the step (4) to dryness, placing the filter cake into a solid phase extraction column, eluting the filter cake, and collecting an elution solvent;
(6) adding acidic ionic liquid into the eluent obtained in the step (5) and removing a low-boiling-point elution solvent;
(7) and (4) after the solution obtained in the step (6) is subjected to constant volume, determining by adopting ultra-high performance liquid chromatography-tandem mass spectrometry to obtain the content of the N-dimethyl nitrosamine in the water sample.
Further, the speed of suction filtration in the step (4) is 25-100mL/min, and the suction filtration time is 5-20 min.
Further, the eluent used in the step (5) is a low-boiling polar aprotic solvent.
Further, the eluent adopted in the step (5) is one or more combinations of solid phase extraction filler activation solvents in the step (1).
Further, the acidic ionic liquid is N-methylimidazole hydrogen sulfate, N-methylimidazole hydrochloride, 1-ethyl-N-methylimidazole hydrogen sulfate and 1-butyl-N-methylimidazole hydrogen sulfate.
Further, the solid phase extraction filler is coconut shell activated carbon.
Further, the coconut shellThe ratio of the active carbon to the N-dimethyl nitrosamine in the water sample to be detected is 1: 10-9～10-3。
The liquid phase conditions were: liquid phase separation is carried out by using a Waters T3 chromatographic column (the column length is 100mm, the column inner diameter is 2.1mm, and the filler particle size is 1.7 mu m), or the equivalent, the column temperature is set at 40 ℃, the flow rate is 0.4mL/min, the injection volume is 20 mu L, and the mobile phase A: 0.1% aqueous formic acid (v/v), mobile phase B: 0.1% formic acid-acetonitrile (v/v). Liquid phase gradient conditions: 2% -10% of B (0.00min-5.00min), 10% -100% of B (5.00min-5.10min), 100% -100% of B (5.10min-6.10min), 100% -2% of B (6.10min-6.15min), 2% -2% of B (6.15min-8.50 min); the mass spectrum conditions are as follows: atmospheric Pressure Chemical Ionization (APCI), positive ion multi-reaction monitoring mode, capillary voltage 3.0kV, ion source voltage 5500V, ion source temperature 400 ℃, desolvation gas (high-purity nitrogen, > 99%) flow rate 750L/h, collision gas (high-purity argon, > 99%) flow rate 0.15 mL/min.
A kit for measuring N-dimethyl nitrosamine in water is characterized in that: the kit comprises 2.0 g/bag of coconut shell activated carbon powder; 0.5-200 ng/mL of N-dimethyl nitrosamine standard series solution with 7 concentration levels in total, wherein each concentration level contains N-dimethyl nitrosamine-D6The concentration is 10.0 ng/mL; 1.0 mu g/mL of N-dimethylnitrosamine-D6A standard working solution; dichloromethane eluent; an acidic ionic liquid; solid phase extraction empty tube and sieve plate.
A method for monitoring N-dimethyl nitrosamine is used for detecting source water, factory water and drinking water.
The invention has the advantages that:
firstly, the pretreatment time of the sample is greatly shortened, the literature method adopts a solid phase extraction column (2g/6mL), generally, the solid phase extraction column can only pass through the column at a gravity natural flow rate or a vacuum pump at a flow rate of less than 10mL/min, 500mL of water sample can only complete enrichment treatment after about 1 hour, and the enrichment treatment can be controlled within 15 minutes by adopting the method.
Secondly, the adsorption efficiency is greatly improved, the method adopts the ultrasonic-assisted dispersion of the activated carbon to fully disperse the activated carbon and the N-dimethyl nitrosamine in the water, the contact area and the contact time are increased, and the problems of short contact time and low adsorption efficiency caused by the rapid passing of an extraction column are solved.
And thirdly, the loss of the N-dimethyl nitrosamine in the sample processing process is reduced, the accuracy of the detection result is greatly improved, the quantitative detection limit is reduced, the average recovery rate of three different concentration addition levels is 97.0-100.8%, the precision of the method is 0.6-3.0%, and the detection limit can reach 2.0 ng/L. The prior literature technology mainly adopts a GC-MS method for determining N-dimethyl nitrosamine in drinking water, but LC-MS/MS shows unique superiority when analyzing substances with strong polarity and poor thermal stability, and has higher instrument sensitivity and stronger matrix interference resistance. Due to the difference of GC-MS and LC-MS/MS sampling solution systems, the sample processing program of GC-MS cannot be completely used for LC-MS/MS method determination. The GC-MS method can be directly injected for analysis after collecting dichloromethane eluent, but the LC-MS/MS method can be injected for analysis after volatilizing dichloromethane components and redissolving by using an initial mobile phase. The dichloromethane eluent is usually concentrated by rotary evaporation, and the N-dimethyl nitrosamine has low boiling point and inevitably causes N-dimethyl nitrosamine loss in the reduced pressure distillation process, so that the recovery rate in the actual analysis is low Simple and easy to operate. Meanwhile, the problems of environmental pollution and poor fixing effect caused by volatile organic acids such as formic acid, acetic acid and the like are also avoided.
And fourthly, a rapid kit suitable for on-site sampling is developed and used for aiming at the characteristics of low boiling point and difficult preservation of the N-dimethyl nitrosamine. The reagent kit comprises standard series working solution, various sampling instruments, consumables, sodium thiosulfate, activated carbon powder and the like, and can realize on-site sampling, treatment and storage of a water sample by matching with a suction filter and a small ultrasonic instrument, and the detection can be realized only by bringing the pretreated sample liquid back to a laboratory for concentration subsequently, so that the loss of N-dimethyl nitrosamine in the sampling and transporting processes is greatly reduced, and the accuracy of the result is improved.
Drawings
FIG. 1 is a flow chart of the pretreatment operation.
Figure 2 is a graph of the effect of different ion sources on NDMA ionization efficiency.
FIG. 3 is a graph showing the effect of different pretreatment methods on NDMA recovery.
FIG. 4 is a graph showing the effect of different suction filtration rates on NDMA recovery.
FIG. 5 is a graph showing the effect of different rotary evaporation temperatures on NDMA recovery.
FIG. 6 is a multiple reaction monitoring plot of method blank (A) and 6.0ng/L plus standard (B).
FIG. 7 is a schematic diagram of the use of the kit of the present invention.
Detailed Description
The following detailed description further describes the present invention for the purpose of illustrating the technical solutions and objects of the present invention.
Screening of test conditions
Liquid chromatography conditions: the method is mainly optimized for the types of the packing of the separation column, and two common packing chromatographic columns such as BEH C18 and HHS T3 are respectively compared. The results show that the NDMA peak area, the retention effect, the peak shape and the like of the two have no significant difference, but under the condition of the same flow rate of 0.4mL/min, the column pressure of the T3 column is far less than that of the C18 column, and the T3 column is selected as the chromatographic column in consideration of the running stability and tolerance degree of the instrument.
Mass spectrum detection conditions: NDMA has small molecular weight and strong polarity, and the ionization efficiency of NDMA is obviously influenced by ion source species. The experiment used NDMA standard solutions of the same concentration (100.0ng/mL) to compare APCI and ESI sources, and evaluated ion source suitability, primarily by response intensity (peak height) and quantitative ion signal-to-noise ratioThe results are shown in FIG. 2. From the graph, it can be found that NDMA responds to intensity under ESI source ionization conditions (10)4Level) and noise performance (signal-to-noise ratio of only 10.9) are far less than those of APCI sources (10 respectively)6Class, signal to noise ratio in excess of 700), APCI sources are all better suited for NDMA measurements than ESI sources.
Two common solid phase extraction columns were compared, including an Oasis HLB column (200mg, 6mL) and a coconut shell activated carbon column (2g, 6 mL). The test condition is that 50ng/L of standard water sample is used for testing through the solid phase extraction column, and the elution condition is recommended by the instruction for both the two types of solid phase extraction columns. The results (as in fig. 3) show that the HLB column has little adsorption to NDMA, mainly due to NDMA itself being too polar; the recovery rate of the coconut shell activated carbon column is more than 90%, and the characteristics of large specific surface area, developed pore structure and strong adsorption performance of the coconut shell activated carbon are proved to be very suitable for enriching NDMA.
Optimizing an ultrasonic-assisted dispersion solid-phase extraction method, wherein the most critical to the result is the suction filtration speed of the suspension, and the high speed can cause insufficient contact between NDMA (N-methyl-ammonium) in a water sample and coconut shell activated carbon; too slow a speed will increase the time required for the experiment, and the results are shown in fig. 4. It was found that the recovery rate was maintained at about 80% when the suction filtration rate was less than 50mL/min, but decreased to about 50% when the suction filtration rate reached 100 mL/min. When the speed exceeds 250mL/min, the filter membrane is very easy to perforate and the recovery rate is almost zero. Finally, the suction filtration speed is set to 50mL/min to take account of the experimental speed and the recovery rate.
The experiment compares the elution effects of four organic reagents on NDMA on a coconut shell activated carbon column, namely dichloromethane, chloroform, acetonitrile and methanol. Each solvent was eluted at 5.0 mL/time for 3 times. The results show that the recovery rate after elution of dichloromethane reaches 100.8% + -4.2%, the recovery rate of chloroform is 76.4% + -1.0%, and both acetonitrile and methanol are less than 60%. Meanwhile, the time required by the subsequent rotary evaporation of the elution solvent is also one of the measurement indexes, wherein the time required by the concentration of dichloromethane is about 5min, the chloroform is about 25min, and the methanol and the acetonitrile both need more than 30 min. In view of the above, dichloromethane was finally selected as the eluting solution.
The rotary evaporation temperature also has an important influence on the recovery rate of the whole concentration step, the evaporation speed of dichloromethane can be increased when the temperature is higher, and although the concentration time can be shortened, dichloromethane is easy to boil and NDMA volatilization loss is easily caused; lower temperatures, while reducing NDMA loss, extend the time required for rotary evaporation. This experiment compares six different temperatures (n-3) from 20 ℃ to 45 ℃ and the like, and the results are shown in fig. 5. While spin-evaporation times of 45 ℃ can be reduced to within 2min, NDMA is subject to greater evaporation losses, and it is recommended that the spin-evaporation temperature be controlled to within 20 ℃ to 25 ℃ (about 5 to 6min for a single sample). It is noted that in the LC-APCI-MS/MS system, the water coexisting during elution does not need to be removed, and this part of water is in an acidic condition under the action of the acidic ionic liquid, and can protect NDMA during the spin-steaming process, reducing its loss due to volatilization, this step also has a significant impact on the overall pretreatment operation recovery, and compatibility with aqueous solutions is also a point where the liquid quality is superior to that of the conventional GC-MS/MS method.
Based on the above screening conditions, sample pretreatment was carried out as follows
Accurate transfer of NDMA and NDMA-D6Standard working solution is prepared into standard series (containing NDMA-D) of 0.5ng/mL, 1.0ng/mL, 2.5ng/mL, 10.0ng/mL, 50.0ng/mL, 100.0ng/mL and 150.0ng/mL by using pure water6Concentration of 10.0ng/mL), then 2.0g of coconut shell activated carbon powder was weighed and activated and equilibrated with 3 mL. times.5 times, 3 mL. times.3 times, and 3 mL. times.3 times, respectively, of dichloromethane in this order. And then adding the mixture into a water sample to be detected, uniformly stirring, and performing ultrasonic-assisted dispersion extraction for 10min, wherein the stirring is performed once in the period of 5 min. After extraction, the suspension is filtered by a 1.2-micron water-phase microporous membrane at a speed of 50mL/min (i.e. the total filtering time is controlled to be about 10 min). After the suction filtration is finished, continuously extracting air for 3min, then recovering the filler to a solid phase extraction column, eluting with dichloromethane 3mL multiplied by 4 times, collecting all the eluent, and then performing rotary evaporation at 20 ℃, wherein the rotary evaporation negative pressure is carefully controlled during the process, so that the organic phase is prevented from being vigorously boiled. Continuing rotary evaporation for 10s after dichloromethane is completely evaporated, oscillating pear-shaped flask to make water phase fully rinse the wall of the flask, transferring water solution, and fixing with ultrapure waterThe volume is reduced to 1.0mL, and the solution is filtered by using a 0.22 mu m aqueous phase microporous filter membrane in a sample injection bottle to be measured.
Liquid phase separation is carried out by using a Waters T3 chromatographic column (the column length is 100mm, the column inner diameter is 2.1mm, and the filler particle size is 1.7 mu m), or the equivalent, the column temperature is set at 40 ℃, the flow rate is 0.4mL/min, the injection volume is 20 mu L, and the mobile phase A: 0.1% aqueous formic acid (v/v), mobile phase B: 0.1% formic acid-acetonitrile (v/v). Liquid phase gradient conditions: 2% -10% of B (0.00min-5.00min), 10% -100% of B (5.00min-5.10min), 100% -100% of B (5.10min-6.10min), 100% -2% of B (6.10min-6.15min) and 2% -2% of B (6.15min-8.50 min).
Mass spectrum conditions: atmospheric Pressure Chemical Ionization (APCI), positive ion multiple reaction monitoring mode, capillary voltage 3.0kV, ion source voltage 5500V, ion source temperature 400 ℃, desolvation gas (high purity nitrogen,>99%) flow rate of 750L/h, collision gas (high purity argon,>99%) flow rate 0.15 mL/min. NDMA and isotope internal standard NDMA-D thereof6Mass spectrometry conditions refer to table 1.
TABLE 1 NDMA and NDMA-D6Multiple reaction monitoring conditions
Figure BDA0002379545720000061
The final linear correlation coefficient (r) is greater than 0.9999. The sensitivity test result of the method is shown in FIG. 6, wherein the signal-to-noise ratio of the blank signal of the method is controlled to be about 6.3, and the signal-to-noise ratio of the NDMA in the standard water sample of 6.0ng/L can reach about 20. It should be noted that NDMA in the method blank is mainly suspected to be derived from coconut shell activated carbon filler, on the other hand, a small peak behind NDMA is an exogenous interference component in dichloromethane, baseline separation can be realized under the current experimental conditions, and the quantitative result is not enough to be obviously influenced.
The accuracy and precision results of the method are carried out in actual water sample matrixes (domestic drinking water and source water), wherein the background value and low, medium and high level standard adding tests of the water sample are respectively carried out for 6 times of parallel experiments, and the specific results of the accuracy and the precision are shown in tables 2 to 3. It can be found that the accuracy and precision results of the method shown in the high-low three-level standard adding test are satisfactory.
TABLE 2 accuracy and precision test results of the method in domestic drinking water
Figure BDA0002379545720000071
TABLE 3 accuracy and precision test results of the method in water source
Figure BDA0002379545720000072
And detecting the actual water sample according to the optimized method, and subtracting the blank background value of the method from the detection result. In the experiment, 16 parts of source water, 14 parts of factory water samples and 18 parts of terminal water are collected (the results are shown in table 4), wherein only three water sample detection values are close to the background value of the method, and all other water samples are higher than the blank background value. It was found that only three negative samples were source water, indicating that the raw water may not contain NDMA before being treated, which is also consistent with the tap water disinfection protocol.
TABLE 4 actual sample measurement results
Sample type Sample number (parts) Number of detected persons (number of copies) Result Range (ng/L)
Source water 16 13 +a-14.4
Delivery water 14 14 +a-13.8
Peripheral water 18 18 +a-11.2
aThe result is between 2.0ng/L and 6.0ng/L, and the product is positive.
The method has the detection limit: when the sample volume was 500mL, the detection limit of nitrosodimethylamine was 2.0ng/L and the quantitation limit was 6.0 ng/L.
The method uses coconut shell activated carbon powder, adopts ultrasonic-assisted dispersion solid phase extraction to enrich and concentrate NDMA in the drinking water, and then uses dichloromethane for elution after rapid suction filtration. The whole pretreatment process is simple to operate, few in influencing factors, and satisfactory in stability, sensitivity and result accuracy. The method has the following defects: because the NDMA content in drinking water is very low, usually in ng/L grade, the NDMA concentration method has higher requirements on concentration times and instrument sensitivity.
And finally determining the related technical indexes of the method according to the verification result of the unit methodology developed by the method. The method is suitable for drinking water and water substrates of water sources, and when the sampling volume is 500mL, the detection limit of N-dimethyl nitrosamine is 2.0ng/L, and the quantification limit is 6.0 ng/L. The working linear range of the method is usually 0.5-200.0ng/mL, the accuracy and precision result of the method is satisfactory, and the average standard addition recovery rate under the conditions of three different concentration levels is 97.0-98.8% (domestic drinking water), 99.5-100.8% (source water), and the RSD is 0.6-2.3% (domestic drinking water) and 0.6-3.0% (source water).
48 parts of samples (including 16 parts of source water, 14 parts of leaving water and 18 parts of peripheral water) are collected together, and the detected concentration is in the range of 6.0ng/L-14.4 ng/L. Subsequently, the results of relevant experiments carried out by a plurality of inspection institutions show that the analysis method has strong applicability, is stable and reliable, has sensitivity indexes meeting the limit requirement below the relevant standard of 10ng/L, and meets the detection requirement of the N-dimethyl nitrosamine compound in the drinking water and the source water thereof.
The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (9)

1. A method for measuring N-dimethyl nitrosamine in water is characterized by comprising the following steps:
(1) pre-activating the solid-phase extraction filler;
(2) adding sodium thiosulfate and an isotope internal standard working solution into a water sample to be detected to obtain a detection solution;
(3) mixing the solution to be detected obtained in the step (2) with the solid-phase extraction filler in the step (1) for ultrasonic dispersion extraction;
(4) carrying out suction filtration on the mixed suspension solution obtained in the step (3) to obtain a filter cake;
(5) pumping the filter cake obtained in the step (4) to dryness, placing the filter cake into a solid phase extraction column, eluting the filter cake, and collecting an elution solvent;
(6) adding acidic ionic liquid into the eluent obtained in the step (5) and removing a low-boiling-point elution solvent;
(7) and (4) after the solution obtained in the step (6) is subjected to constant volume, determining by adopting ultra-high performance liquid chromatography-tandem mass spectrometry, and calculating to obtain the content of the N-dimethyl nitrosamine in the water sample.
2. A method for determining N-dimethyl nitrosamine in water as claimed in claim 1, wherein, in said step (4), the suction filtration speed is 25-100mL/min, and the suction filtration time is 5-20 min.
3. A method for determining N-dimethyl nitrosamine in water as claimed in claim 1, wherein said eluent used in step (5) is a low boiling polar aprotic solvent.
4. A method for determining N-dimethyl nitrosamine in water as claimed in claim 1, wherein said eluent used in step (5) is one or more combinations of solid phase extraction filler activating solvents in step (1).
5. A method for determining N-dimethylnitrosamines in water as claimed in claim 1, wherein said acidic ionic liquid is N-methylimidazole hydrogensulfate, N-methylimidazole hydrochloride, 1-ethyl-N-methylimidazole hydrogensulfate and 1-butyl-N-methylimidazole hydrogensulfate.
6. A method for determining N-dimethyl nitrosamine in water as claimed in claim 1, wherein said solid phase extraction filler is coconut shell activated carbon.
7. The method for determining N-dimethyl nitrosamine in water as claimed in claim 6, wherein the ratio of coconut shell activated carbon to N-dimethyl nitrosamine in water sample to be tested is 1: 10-9～10-3。
8. A method for determining N-dimethylnitrosamines in water as claimed in claim 1, wherein the liquid phase conditions are: adopting a Waters T3 chromatographic column, wherein the length of the chromatographic column is 100mm, the inner diameter of the chromatographic column is 2.1mm, and the grain diameter of a filler is 1.7 mu m; the chromatographic column is used for liquid phase separation, the column temperature is set at 40 ℃, the flow rate is 0.4mL/min, the sample injection volume is 20 mu L, and the mobile phase A: 0.1% aqueous formic acid (v/v), mobile phase B: 0.1% formic acid-acetonitrile (v/v); the liquid phase gradient conditions were: 2% -10% of B at 0.00-5.00 min, 10% -100% of B at 5.00-5.10 min, 100% -100% of B at 5.10-6.10 min, 100% -2% of B at 6.10-6.15 min, 2% -2% of B at 6.15-8.50 min;
the mass spectrum conditions are as follows: atmospheric Pressure Chemical Ionization (APCI), a positive ion multi-reaction monitoring mode, a capillary voltage of 3.0kV, an ion source voltage of 5500V, an ion source temperature of 400 ℃, desolvation gas of 99% high-purity nitrogen, and a flow rate of 750L/h; the collision gas was > 99% high purity nitrogen at a flow rate of 0.15 mL/min.
9. A method for the determination of N-dimethylnitrosamines in water according to any one of claims 1 to 8, characterized in that: the method is suitable for detecting source water, factory water and drinking water.
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