National Ecological and Environmental Standards of the People's Republic of China
hj 1333-2023
Water qualityDetermination of perfluorooctane sulfonic acid and perfluorooctanoic acid and their salts
Isotope dilutionLiquid chromatographyTriple quadrupole mass spectrometry
water quality-determination of perfluorooctanesulfonic acid
perfluorooctanoic acid and their salts-isotope dilution liquid
chromatography-triple quadrupole mass spectrometry
Foreword
This standard is formulated in order to implement the "Environmental Protection of the People's Republic of China", the "Water Pollution Prevention and Control Law of the People's Republic of China" and the "Marine Environmental Protection of the People's Republic of China" to prevent and control ecological environmental pollution, improve the quality of the ecological environment, and standardize the determination methods of perfluorooctane sulfonic acid and its salts in water, perfluorooctanoic acid and its salts.
This standard specifies isotope dilution liquid chromatography-triple quadrupole mass spectrometry for the determination of straight-chain perfluorooctane sulfonic acid and its salts, and linear perfluorooctanoic acid and its salts in surface water, groundwater, domestic sewage, industrial wastewater and seawater.
Appendix A Appendix C of this standard is an informational appendix.
This standard is being published for the first time.
This standard is formulated by the Department of Ecological Environment Monitoring and the Department of Regulations and Standards of the Ministry of Ecology and Environment.
The main drafting units of this standard: the National Environmental Analysis and Testing Center, the Foreign Cooperation and Exchange Center of the Ministry of Ecology and Environment, and the Chinese Academy of Environmental Sciences.
Verification units of this standard: Zhejiang Provincial Ecological Environment Monitoring Center, Guangdong Provincial Ecological Environment Monitoring Center, Hubei Provincial Ecological Environment Monitoring Center Station, Jiangsu Taizhou Environmental Monitoring Center, Shandong Provincial Analysis and Testing Center and Zhongzhi Yidia (Beijing) Environmental Testing and Analysis Co., Ltd
This standard was approved by the Ministry of Ecology and Environment on December 5, 2023.
This standard will be implemented from July 1, 2024.
This standard is interpreted by the Ministry of Ecology and Environment.
Scope of application
This standard specifies the isotope dilution liquid chromatography-triple quadrupole mass spectrometry method for the determination of perfluorooctane sulfonic acid and its salts, perfluorooctanoic acid and its salts in water.
This standard applies to straight-chain perfluorooctanesulfonic acid and its salts in surface water, groundwater, domestic sewage, industrial wastewater and seawater.
Perfluorooctanesulfonic acid and perfluorooctanesulfonate (PFOs), linear perfluorooctanoic acid and perfluorooctanoate (PFOA).
The sample size is 05 l, the volume is 10 ml with an injection volume of 5At 0 L, the detection limit of PFOS (measured by the concentration of the corresponding acid) is 06 ng l, the lower limit of determination is 24 ng L, PFOA (measured by the concentration of the corresponding acid) method has a detection limit of 05 ng l with a lower limit of determination of 20 ng/l。
Normative references
This standard refers to the following documents or their provisions. Where a dated reference is made, only the dated version applies to this standard.
The most recent version of an undated reference (including all change orders) applies to this standard.
gb 17378.3 Marine Monitoring Code Part 3: Sample Collection, Storage and Transport.
hj 91.1 Technical specifications for sewage monitoring.
hj 91.2. Technical specifications for surface water environmental quality monitoring.
HJ 164 Technical Specification for Groundwater Environmental Monitoring.
hj 442.3 Technical Specifications for Environmental Monitoring in Coastal Waters Part III: Water Quality Monitoring in Coastal Areas.
Methodological principle
PFOS and PFOA in the samples were enriched and purified by weak anion-exchange solid-phase extraction column, determined by liquid chromatography-triple quadrupole mass spectrometry, and quantified by isotope dilution according to retention time, characteristic ion abundance ratio, and isotope dilution.
Interference and elimination
4.1 The use of fluoropolymers (e.g., PTFE) may interfere with the assay, and fluoropolymer-based utensils should be avoided during sample collection and preparation.
4.2 Branched isomers may interfere with the assay, and chromatographic conditions should be optimized to effectively separate branched and straight-chain PFOS and PFOAs. Chromatograms of PFOS and PFOA linear versus branched isomers are shown in Appendix A.
4.3 The LC system may contain PFOA, and the PFOA in the sample can be separated from the background of the instrument by using the trap column, see Appendix B for the schematic diagram of the installation position of the trap column of the LC system; The PTFE accessories in the LC system can also be replaced with polyetheretherketone or stainless steel.
4.4. On the premise of meeting the detection limit of the method, the sample amount can be appropriately reduced to reduce the sample matrix effect.
Reagents and materials
Unless otherwise stated, the analysis uses analytical pure reagents that meet national standards, and the experimental water is pure water that does not contain the target compound.
5.1 Methanol (CH3OH): chromatographically pure.
5.2 Acetic acid (CH3COOH): chromatographically pure.
5.3 Ammonia (NH3·H2O): W [25%, 28%].
5.4 Ammonium acetate (CH3COONH4): Superior pure.
5.5 Ammonia-methanol mixed solution.
With ammonia (53) and methanol (51) Mix according to the volume ratio of 2:98, and use it on the spot.
5.6 Ammonium acetate in water: C(CH3CoonH4) 2 mmolL.
Weigh 154 mg of ammonium acetate (54) Add 1000 ml of water, mix well, and prepare for temporary use.
5.Ammonium acetate buffer: pH 4.
Weigh 387 mg of ammonium acetate (54), add 1143 ml acetic acid water, mix well.
5.8 PFOS Standard Stock Solution: 500 μg/ml。
Commercially available certified standard solutions should be stored in accordance with the requirements of the standard solution certificate, and should be restored to room temperature and shaken well before use.
5.9 PFOS Standard Solution: 100 μg/ml。
Pipette the appropriate amount of PFOS standard stock solution (5.)8), with methanol (51) Dilution, PFOS standard use liquid sealing, protect from light, refrigeration below 4 can be stored for 60 days.
5.10 PFOA standard stock solution: =500 μg/ml。
Commercially available certified standard solutions should be stored in accordance with the requirements of the standard solution certificate, and should be restored to room temperature and shaken well before use.
5.11 PFOA Standard Solution: 100 μg/ml。
Pipette the appropriate amount of PFOA standard stock solution (5.)10) with methanol (51) Dilution, PFOA standard use liquid sealing, protect from light, refrigeration below 4 can be stored for 60 days.
5.12 Extraction of internal standard mixed stock solution: 200 μg/ml。
The use of carbon isotope labeled perfluorooctane sulfonic acid or its salts (13C4-PFOS) and carbon isotope labeled perfluorooctanoic acid or its salts (13C4-PFOA) as extraction internal standards, commercially available certified standard solutions, stored in accordance with the requirements of the standard solution certificate, should be restored to room temperature and shaken well before use.
5.13 Extract the solution used for internal standards: 0200 μg/ml。
Pipette an appropriate amount of the internal standard mixed stock solution (5.)12) with methanol (51) Dilution, extraction of the internal standard with liquid sealing, protected from light, refrigeration below 4 can be stored for 60 days.
5.14 Injection Internal Standard Stock Solution: 500 μg/ml。
Carbon isotope-labeled perfluorooctanoic acid or its salts (13C2-PFOA) were used as the internal standard for injection, and the commercially available certified standard solution should be stored in accordance with the requirements of the standard solution certificate, and should be restored to room temperature and shaken well before use.
5.15 Injection internal standard solution: 0200 μg/ml。
Pipette the appropriate amount of the injected internal standard stock solution (5.)14) with methanol (5.)1) Dilution, the injection of the internal standard should be sealed with liquid, protected from light, and refrigerated below 4 for 60 days.
Weak anion-exchange solid-phase extraction column: The packing material is piperazine-bonded N-vinylpyrrolidone-divinylbenzene copolymer,
150 mg/6 ml, or other equivalent solid-phase extraction columns.
5.17 Weak Anion-Exchange SPE Columns: N-vinylpyrrolidone-divinylbenzene copolymer bonded with piperazine, 500 mg 6 mL, or other equivalent SPE columns.
5.18 Membrane: glass fiber or quartz material, 045 μm。
5.19 Syringe filter: polypropylene or nylon, 022 μm、0.45 μm。
5.20 Nitrogen: Purity 9999%。
Instruments and equipment
6.1 Sampling bottle: polypropylene or polyethylene, 1 l.
6.2 Liquid chromatography-triple quadrupole mass spectrometer: The liquid chromatograph has a gradient elution function, and the triple quadrupole mass spectrometer is equipped with an electrospray ion source and has a multi-reaction monitoring function.
6.3 Column:The filler is eighteen alkyl silane bonded silica gel, and the particle size of the filler ism, the column length is100 mm, the inner diameter is2.1 mm。or other columns with similar performance.
6.4. Trapping column: The packing material is octadecylsilane bonded silica gel, and the particle size of the packing material is 18 m 5 m, column length 50 mm, inner diameter 21 mm。or other columns with similar performance.
6.5 SPE device: The enrichment line and SPE column adapter are made of polypropylene.
6.6. Water sample suction filtration device: polysulfone resin and other materials, avoid using glass materials.
6.7. Concentrator device: nitrogen blowing concentrator or other equipment with equivalent performance.
6.8 Beaker: Polypropylene.
6.9 Measuring cylinder: Polypropylene.
6.10 Tubes: Polypropylene.
6.11 vial: polypropylene, 2 ml.
6.12 Volumetric flask: Polypropylene.
6.13 Instruments and equipment commonly used in general laboratories.
Samples
7.1 Sample collection and storage.
In accordance with GB 173783、hj 91.1、hj 91.2. HJ 164 and HJ 4423 The relevant provisions for the collection of samples. Place the sample in a sampling bottle (6.)1) Medium, sealed, protected from light, refrigerated storage below 4, and the preparation of samples should be completed within 14 days.
Samples should be collected at the same time as the full program blank sample. Use a sampling bottle (61) Fill the water belt to the sampling site, and transfer the water to another sampling bottle (6.)1) as a blank sample for the whole procedure, which is stored and transported to the laboratory along with the actual sample.
7.2 Preparation of specimens.
7.2.1 Filtering.
Measure 500 ml of sample (71) in a beaker (68) Medium, add 500 l of the solution used for the extraction of internal standards (5.)13), mix well, use a water sample suction filter device (66) and filter membranes (518) Filtration. After filtration, acetic acid (52) or ammonia (53) Adjust the pH to 6-8.
7.2.2 Solid phase extraction.
Sequentially mix the solution with 6 ml ammonia-methanol and then with methanol (51) and 6 ml of water-activated weak anion-exchange solid-phase extraction columns (5.)16) During the activation process, it should be ensured that the solid-phase extraction column packing is not exposed to air. The filtered sample (72.1) After passing through the SPE column at a flow rate of 3 ml min and 5 ml min, sequentially apply 6 ml of water and 8 ml of ammonium acetate buffer (57) Rinse the solid phase extraction column and discard the eluent. With nitrogen (520) Purge or solid phase extraction device (6.)5) The vacuum pump pumped air to dry the solid phase extraction column for 10 min to remove the residual water in the column. Use 8 ml of methanol (51) Rinse the SPE column at a flow rate of 1 ml min and 3 ml min and discard the eluent. Then use 6 ml of ammonia-methanol mixture solution (55) Elute the solid-phase extraction column at a flow rate of 1 ml min and 3 ml min, and collect the eluent in a centrifuge tube (610) Medium.
Note: Weak anion-exchange solid-phase extraction columns (5.) can be used17), or reduce the sample size to prevent packing penetration.
7.2.3 Concentrate.
With a concentrator (67) Replace the eluate (72.2) Concentrate until nearly dry, add 500 l of the solution used for the injection of internal standards (5.)15) with methanol (51) Adjust the volume to 10 ml, mixed through a syringe filter (519) Filter to the injection vial (6.)11) Medium, sealed, protected from light, refrigerated storage below 4, and the analysis was completed within 28 days.
7.3. Preparation of blank specimens.
Replace the sample with water, in accordance with the preparation of the sample (7.)2) Prepare the laboratory blank specimen in the same procedure.
Analyze the steps
8.1 Instrument Reference Conditions.
8.1.1 Liquid chromatography reference conditions.
Mobile phase A: methanol (5.)1）；Mobile phase B: ammonium acetate in water (5.)6）；Column temperature: 35; Injection volume: 50 μl；Flow rate: 03 ml/min；The gradient elution procedure is shown in Table 1.
8.1.2 Mass spectrometry.
8.1.2.1 Mass spectrometry reference conditions.
Electrospray ion source, negative ion mode; Monitoring method: multi-reaction monitoring; Capillary voltage: 2500 V; Vacuum interface temperature: 200 °C; Desolvator temperature: 350 °C; Atomized gas flow: 10 l/min；Desolvator flow: 15 l min; Back-blowing air flow: 15 l/min；Collision airflow: 025 ml/min。The conditions for multiple reaction monitoring are shown in Table 2.
8.1.2.2 Tuning of the mass spectrometer.
Tuning the instrument according to the instrument manual and confirming the performance of the instrument, and measuring the sample after the instrument performance is normal.
8.2 Calibration.
8.2.1 Preparation and determination of standard series.
Pipette the appropriate amount of PFOS standard solution (59) and PFOA standard solution (511) in a 5 ml volumetric flask (612). Add 250 l of the solution used for extracting the internal standard (513) and 250 l of the solution used for the injection internal standard (515) with methanol (51) Constant volume, prepared to a concentration of 100 ng/ml、2.00 ng/ml、5.00 ng/ml、10.0 ng/ml、20.0 ng/ml、50.Standard series of 0 ng ml, 100 ng ml (this is the reference concentration). According to the instrument reference conditions (81) Inject sequentially from low concentration to high concentration. The retention time and quantification of the peak area of each target compound, extracted internal standard, injection internal standard were recorded. The total ion chromatograms of PFOS and PFOA are shown in Figure 1.
8.2.2 Average relative response factor calculation.
The relative response factor of the target compound i is calculated according to equation (1).
where: rrfs,ij - the relative response factor of the target compound i at point j in the standard series;
as,ij – the peak area of the quantified ion of the target compound i at point j in the standard series;
AES,IJ - the peak area of the target compound i at point j in the standard series corresponding to the quantified ions of the extracted internal standard;
ES,IJ - the mass concentration of the extracted internal standard corresponding to the target compound i at point j in the standard series, ng ml;
S,ij – the mass concentration of target compound i at point j in the standard series, ng ml.
The mean relative response factor for target compound i is calculated according to equation (2).
where: rrfs,i - the average relative response factor of target compound i;
rrfs,ij – the relative response factor of target compound i at point j in the standard series;
n - the number of points in the standard series.
The relative response factor of the extracted internal standard corresponding to the target compound i was calculated according to equation (3).
Where: rrfes,ij - the relative response factor of the target compound i at point j in the standard series corresponding to the extraction of the internal standard;
AES,IJ - the peak area of the target compound i at point j in the standard series corresponding to the quantified ions of the extracted internal standard;
AIS,J – the peak area of the internal standard quantification ion injected at point J in the standard series;
is,j - mass concentration of the internal standard injected at point j in the standard series, ng ml;
ES,IJ - the mass concentration of the extracted internal standard corresponding to the target compound i at point j in the standard series, ng ml;
The average relative response factor of the extracted internal standard corresponding to the target compound i was calculated according to equation (4).
where: rrfes, i - the average relative response factor of the extracted internal standard corresponding to the target compound i;
rrfes,ij - the relative response factor of the extracted internal standard corresponding to the j-point target compound i in the standard series;
n - the number of points in the standard series.
8.3. Specimen determination.
In accordance with the preparation and determination of the standard series (82.1) Determine the specimen under the same instrumental conditions (72）。
8.4 Blank test.
In accordance with the determination of the specimen (83) Determination of laboratory blank specimens under the same instrumental conditions (73）。
Calculation and presentation of results
9.1 Qualitative analysis.
Qualitative analysis based on retention time to ion abundance ratio. The retention time of the target compound should be consistent with the retention time of the corresponding extraction internal standard in the sample. When the absolute deviation is within 30%, it can be judged that the target compound is present in the sample.
The relative abundance of the qualitative ions of the target compound i in the sample is calculated according to equation (5).
Where: ksam,i - relative abundance of qualitative ions of target compound i in the sample, %;
asam2,i - the peak area of the qualitative ion of the target compound i in the sample;
ASAM1,I – the peak area of the quantified ions of target compound I in the sample.
The relative abundance of the target compound I qualitative ions in the standard solution is calculated according to equation (6).
where: kstd,i - the relative abundance of the qualitative ions of the target compound i in the standard solution, %;
ASTD2,I – the peak area of the target compound I qualitative ion in the standard solution;
ASTD1,I – Peak area of target compound I quantified ions in standard solution.
9.2 Result calculation.
9.2.1 Calculation of the mass of the extracted internal standard in the sample.
The mass concentration of the extracted internal standard corresponding to the target compound i in the sample is calculated according to equation (7).
Where: es,i - the mass concentration of the target compound i corresponding to the extracted internal standard in the sample, ng ml;
AES,I - the peak area of the target compound I corresponding to the extracted internal standard quantification ion in the sample;
AIS—the peak area of the injected internal standard quantified ions;
is - the mass concentration of the injected internal standard, ng ml;
rrfes,i - the average relative response factor of the extracted internal standard corresponding to the target compound i.
The mass of the extracted internal standard corresponding to the target compound i in the sample is calculated according to equation (8).
Where: MES,i - the mass of the extracted internal standard corresponding to the target compound i in the sample, ng;
es,i - the mass concentration of the extracted internal standard corresponding to the target compound i in the sample, ng ml;
VC - sample volume, ml.
9.2.2 Calculation of the mass concentration of the target compound in the sample.
The mass concentration of the target compound i in the sample is calculated according to equation (9).
Where: C,I - the mass concentration of the target compound i in the sample, ng ml;
ac,i – the peak area of the quantified ions of the target compound i in the sample;
AES,I - the peak area of the target compound I corresponding to the extracted internal standard quantification ion in the sample;
es,i - the mass concentration of the target compound i in the sample corresponding to the internal standard added for extraction, ng ml;
rrfs, I – the average relative response factor of target compound I.
9.2.3 Calculation of the mass concentration of the compound of interest in the sample.
The mass concentration of the target compound i in the sample (measured as the concentration of the corresponding acid) is calculated according to equation (10).
Where: i - the mass concentration of the target compound i in the sample (measured by the concentration of the corresponding acid), ng l;
c,i - the mass concentration of the target compound i in the sample, ng ml;
VC - sample volume, ml.
v - sample volume, l;
ma,i - the molecular weight of the acid corresponding to the target compound i;
ms,i – the molecular weight of the salt corresponding to the target compound i in the standard solution.
9.3 Result indication.
The number of decimal places in the measurement results is consistent with the method detection limit, and a maximum of 3 significant digits are retained.
Accuracy
10.1 Precision.
The 6 laboratories spiked PFOS and PFOA at 500 ng/l、40.0 ng L, 200 ng L blank samples were measured in 6 replicates: the relative standard deviations within the laboratory were respectively. 3%～15%；The relative standard deviations between laboratories were: 6%～12%；The reproducibility limits were 11 ng/l～1.2 ng/l、5.2 ng/l～7.9 ng/l、33 ng/l～35 ng/l；The reproducibility limits are 20 ng/l～2.2 ng/l、13 ng/l～14 ng/l、56 ng/l～69 ng/l。
The 6 laboratories spiked PFOS and PFOA at 500 ng/l、40.0 ng l and 200 ng l of groundwater, seawater, surface water, domestic sewage and industrial wastewater were measured 6 times: the relative standard deviations in the laboratory were respectively. 3%～21%；The relative standard deviations between laboratories were: 5%～16%；The reproducibility limits were 16 ng/l～2.6 ng/l、8.1 ng/l～17 ng/l、29 ng/l～48 ng/l；The reproducibility limits are 21 ng/l～5.7 ng/l、9.0 ng/l～21 ng/l、30 ng/l～103 ng/l。
The method precision results are shown in Table C1。
10.2 Correctness.
The 6 laboratories spiked PFOS and PFOA at 500 ng/l、40.0 ng l, 200 ng l blank sample 6 replicates: spike rate ranges were. 0%～105%；The final values of the spike rate are respectively. 1%±22%～99.0%±17%。
The 6 laboratories spiked PFOS and PFOA at 500 ng/l、40.0 ng l and 200 ng l of groundwater, seawater, surface water, domestic sewage and industrial wastewater and other unified actual samples were repeated 6 times: the spike rate ranges were. 9%～123%；The final values of the spike rate are respectively. 9%±29%～107%±12%。
The extraction of internal standard ** rate ranges from 403%～155%。
The method correctness results are shown in Table C. in Appendix C2。
Quality assurance and quality control
11.1 Blank test.
Analyze at least 1 full-procedure blank and 1 laboratory blank per 20 or batch samples (less than 20), and the blank test results should be below the method detection limit.
11.2 Calibration.
The relative standard deviation of the relative response factor should be 20%, otherwise the cause should be found, the standard series should be redetermined, and the relative response factor should be calculated.
The standard solution at the intermediate point of the standard series was selected for continuous calibration, and the relative error of the measurement results should be within 20% for every 20 samples analyzed or 1 time per batch of samples (less than 20).
11.3 Parallelism.
At least 1 parallel sample should be analyzed for every 20 samples or per batch (less than 20), and the relative deviation of the parallel sample determination results should be within 30%.
11.4 Substrate spiking.
At least 1 matrix spiked sample should be analyzed for every 20 samples or per batch (less than 20), and the spike rate should be between 60% and 130%.
11.5. Extraction of internal standard ** rate.
The extraction of internal standard ** rate should be between 40% and 160%.
Waste disposal
The waste generated in the experiment should be collected, classified and preserved, and the corresponding identification should be done and disposed of according to law.
Precautions
Glass containers may adsorb target compounds, and glass vessels should be avoided during sampling and analysis.
*From: