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HJ 977-2018 English PDF

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HJ 977-2018: Water quality - Determination of alkylmercury - Purge and Trap / gas chromatography cold vapor atomic fluorescence spectrometry
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Basic data

Standard ID HJ 977-2018 (HJ977-2018)
Description (Translated English) Water quality - Determination of alkylmercury - Purge and Trap / gas chromatography cold vapor atomic fluorescence spectrometry
Sector / Industry Environmental Protection Industry Standard
Classification of Chinese Standard Z16
Word Count Estimation 13,189
Issuing agency(ies) Ministry of Ecology and Environment

HJ 977-2018: Water quality - Determination of alkylmercury - Purge and Trap / gas chromatography cold vapor atomic fluorescence spectrometry


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Water quality - Determination of alkylmercury - Purge and Trap/gas chromatography cold vapor atomic fluorescence spectrometry National Environmental Protection Standard of the People's Republic Determination of water quality alkyl mercury Purge and trap/gas chromatography-cold atomic fluorescence spectrometry Water quality - Determination of alkylmercury - Purge and Trap/gas chromatography cold vapor atomic fluorescence spectrometry Published on.2018-11-13 2019-03-01 Implementation Ministry of Ecology and Environment released i directory Foreword.ii 1 Scope 1 2 Normative references 1 3 Principle of the method 1 4 interference and elimination..1 5 reagents and materials..2 6 instruments and equipment..3 7 samples..4 8 Analysis step 5 9 Calculation and representation of results 6 10 Precision and Accuracy.7 11 Quality Assurance and Quality Control..8 12 Waste treatment.8 13 Notes.8 Appendix A (informative) Method Precision and Accuracy..10

Foreword

Protecting the ecology in order to implement the Environmental Protection Law of the People's Republic of China and the Law of the People's Republic of China on Water Pollution Prevention The environment, the human health, and the method for determining the determination of alkyl mercury in water, and the development of this standard. This standard specifies the extraction and capture of alkyl mercury in surface water, groundwater, domestic sewage, industrial wastewater and seawater. Gas chromatography - cold atomic fluorescence spectrometry. Appendix A of this standard is an informative annex. This standard is the first release. This standard is formulated by the Department of Eco-Environmental Monitoring, the Department of Regulation and Standards of the Ministry of Ecology and Environment. This standard was drafted. South China Environmental Science Research Institute of the Ministry of Environmental Protection, Qingyuan Environmental Monitoring Station and Lianzhou Environmental Supervision Station. The standard verification unit. China Academy of Environmental Sciences, Guangdong Environmental Monitoring Center, Sichuan Environmental Monitoring Station, Shenzhen Environmental Monitoring Center Station, Jiangmen Environmental Monitoring Center Station and Shaoguan Environmental Monitoring Center Station. This standard is approved by the Ministry of Ecology and Environment on November 13,.2018. This standard has been implemented since March 1,.2019. This standard is explained by the Ministry of Ecology and Environment. 1 Determination of water quality alkyl mercury - Purge and trap/gas chromatography - cold atomic fluorescence spectrometry Warning. Derivatization reagents and reference materials used in the experiments are toxic compounds, reagent preparation and sample preparation The process should be carried out in a fume hood; protective equipment should be worn as required to avoid contact with skin and clothing.

1 Scope of application

This standard specifies the purge and trap/gas chromatography-cold atomic fluorescence spectrometry for the determination of alkylmercury in water. This standard applies to surface water, groundwater, domestic sewage, industrial wastewater and alkyl mercaptan (methylmercury, ethylmercury) in seawater. Determination. When the sampling volume is 45 ml, the detection limits of methylmercury and ethylmercury are both 0.02 ng/L, and the lower limit of determination is 0.08 ng/L.

2 Normative references

This standard refers to the following documents or their terms. For undated references, the valid version applies to this standard. HJ 442 Code for Environmental Monitoring of Coastal Waters HJ/T 91 Surface Water and Wastewater Monitoring Technical Specifications HJ/T 164 Technical Specifications for Groundwater Environmental Monitoring

3 Principle of the method

After the sample is distilled, the alkyl mercury in the distillate is derivatized with sodium tetrapropylborate to form volatile methylpropylmercury and B. Mercaptopropylmermide, after being separated by purging, trapping, thermal desorption and gas chromatography, pyrolyzed into mercury vapor and measured by cold atomic fluorescence Mercury meter detection. According to the retention time qualitative, the external standard method is quantitative.

4 interference and elimination

4.1 Sulfide, water-soluble organic matter (DOM) and chloride ions have negative interference with the determination of alkyl mercury, steaming the sample Distillation can remove or reduce interference. 4.2 Some small organic molecules in samples (such as oil-contaminated samples) will be adsorbed and adsorbed together with alkyl mercury derivatives. The trap tube, after heating and desorption, will have a quenching effect on the atomic fluorescence signal, and should be diluted before distillation and analysis. 4.3 When the concentration of Hg2 in the sample is higher than 440 ng/L, it will cause positive interference to the determination of alkylmercury. It should be diluted and then distilled and divided. Analysis. Note. It is not advisable to separate alkyl mercury and Hg2 by distillation for water bodies with severe mercury contamination. 25 reagents and materials Unless otherwise stated, analytically pure reagents that meet national standards are used for analysis, and laboratory water is not included in the target combination. Pure water of matter. 5.1 Hydrochloric acid. ρ (HCl) = 1.19 g/ml, excellent grade pure. 5.2 Nitric acid. ρ (HNO3) = 1.42 g/ml, excellent grade pure. 5.3 Glacial acetic acid. ρ (CH3COOH) = 1.05 g/ml, excellent grade pure. 5.4 Potassium hydroxide (KOH). 5.5 Sodium acetate (CH3COONa). 5.6 Copper sulfate pentahydrate (CuSO4·5H2O). 5.7 Sodium tetrapropylborate [NaB(C3H7)4]. purity ≥98%, sealed at room temperature and protected from light. 5.8 Hydrochloric acid solution. 1 1. 5.9 Nitric acid solution. 19. 5.10 Potassium hydroxide solution. ρ (KOH) = 20 g/L. Weigh 2.0 g of potassium hydroxide (5.4), dissolve in 100 ml of water, mix and store in a plastic reagent bottle with a screw. 5.11 Sodium tetrapropylborate solution. ρ[NaB(C3H7)4]=10 g/L. Weigh 1.0 g of sodium tetrapropylborate (5.7) and dissolve in 100 ml of potassium hydroxide solution (5.10) pre-cooled to 0 °C ~ 4 °C. Shake well and quickly dispense into a 1.5 ml screw-top glass bottle with a gasket and freeze at -18 °C ± 2 °C to save 6 Months. When used, take a small bottle of reagent and use it when the ice in the bottle melts about half. Melted tetrapropylborate solution Unstable, one-time use. 5.12 Acetic acid-sodium acetate buffer solution. c = 4 mol/L, pH ≈ 6.0. Weigh 32.8 g of sodium acetate (5.5), dissolve in 80 ml of water, add 2 ml of glacial acetic acid (5.3), dilute to 100 ml with water. Stored in plastic reagent bottles, ready for use. 5.13 Saturated copper sulfate solution. Weigh 50 g of copper sulfate pentahydrate (5.6), dissolve in 100 ml of water, mix and store in plastic reagent bottle. Take the upper layer solution. 5.14 Standard stock solution of methylmercury. hydrazine (CH3Hg) = 1.00 mg/L. Purchase a commercially available certified standard solution with methanol as solvent. After opening, refrigerate, protect from light and seal at 4 ° C. Months. 5.15 Ethyl mercury standard stock solution.  (C2H5Hg) = 1.00 mg/L. Purchase a commercially available certified standard solution with methanol as solvent. After opening, refrigerate, protect from light and seal at 4 ° C. Months. 5.16 Mixed standard intermediate solution.  = 10.0 μg/L. Transfer 500 μl of methylmercury standard stock solution (5.14) and ethylmercury standard stock solution (5.15) to 50 ml capacity respectively. Add 250 μl glacial acetic acid (5.3) and 100 μl hydrochloric acid (5.1) to the bottle and dilute to the mark with water. This solution is lined with tape The brown reagent bottle or fluoropolymer bottle of Teflon screw cap can be stored in the dark for less than 4 °C for 8 months. 5.17 Mixed standard use solution I.  = 1.00 μg/L. Pipette 5.00 ml of mixed standard intermediate (5.16) into a 50 ml volumetric flask, add 250 μl glacial acetic acid (5.3) and 100 μl of hydrochloric acid (5.1) was diluted with water to the mark. This solution is in a brown reagent bottle with a Teflon padded screw cap or 3 fluoropolymer bottles can be stored in the dark for less than 4 ° C for 8 months. 5.18 Mixed standard use liquid II.  = 0.10 μg/L. Pipette 500 μl of mixed standard intermediate (5.16) into a 50 ml volumetric flask, add 250 μl glacial acetic acid (5.3) and 100 μl of hydrochloric acid (5.1) was diluted with water to the mark. This solution is in a brown reagent bottle with a Teflon padded screw cap or The fluoropolymer bottle can be stored in the dark for less than 4 ° C for 8 months. 5.19 Mercury standard stock solution.  (Hg2) = 100 mg/L. Purchase a commercially available certified standard solution that can be stored for 2 years below 4°C. 5.20 Mercury standard use solution.  (Hg2) = 10.0 μg/L. Pipette a certain amount of standard stock solution of mercury (5.19), and dilute it to 10.0 μg/L with water. 5.21 Nitrogen. purity ≥ 99.99%. 5.22 Argon. purity ≥ 99.999%.

6 Instruments and equipment

6.1 Distillation unit. with heating and condensing unit, heating temperature range is 120 ° C ~ 150 ° C. Equipped with matching poly four Fluoroethylene retort, receiving bottle and connecting line. 6.2 Purge and trap. use in-situ purge and trap (Fig. 1) or ectopic purge and trap (Fig. 2), trapping tube filling There is a poly(2,6-diphenyl-p-phenylene ether) (Tenax) adsorbent with a particle size of 150 μm to 180 μm. With a flow controller. Fig.1 Schematic diagram of in-situ purge and trapFig.2 Schematic diagram of ectopic purge and trap 6.3 Gas chromatography. 6.4 Column. Packed column. Packing fixative is OV-3, column length 340 mm, inner diameter 1.59 mm, or other equivalent column. Capillary column. the stationary phase is 100% dimethylpolysiloxane, the column length is 15 m, the inner diameter is 0.53 mm, and the film thickness is 0.5 μm. Or other equivalent columns. 6.5 Cracking unit. 6.6 Cold atomic fluorescence mercury detector. 6.7 Sampling bottle. 500 ml or 1 L high density polyethylene bottle with screw, borosilicate glass bottle or fluorinated polyethylene bottle. 6.8 Injection vial. Brown glass bottle with a Teflon padded screw cap. 46.9 Instruments and equipment commonly used in general laboratories.

7 samples

7.1 Sample collection and preservation Samples were collected according to the relevant regulations of HJ/T 91, HJ/T 164 and HJ 442, and the samples were directly collected into the sampling bottles (6.7). in. After sampling, add 4 ml of hydrochloric acid (5.1) per liter of sample. The pH of the sample after acid addition should be 1-2, otherwise it should be increased appropriately. Add hydrochloric acid (5.1), then add 2 ml of saturated copper sulfate solution (5.13), shake well, and use clean polyethylene The bag is sealed with a sample bottle and stored at 4 ° C or less in the dark to avoid storage in a high mercury environment or with a high mercury concentration sample. Save and complete the analysis within 3 days. If only methylmercury is measured, the analysis is completed within 8 days. 7.2 Preparation of samples Measure 45 ml of the sample in a 60 ml retort, add 4.5 ml of water and 500 μl of acetic acid-sodium acetate to the receiving flask. Flush the solution (5.12) and shake well. Pre-set the heating device temperature to 125 ° C ~ 130 ° C, connect the distillation bottle with a Teflon pipeline and receive Bottle to ensure the retort is sealed. First put it into a distillation bottle for heating. When the vapor enters the receiving bottle, put the receiving bottle into the cooling device. Set to prevent the liquid in the receiving bottle from freezing. When about 80% of the sample is distilled off (the volume of the solution in the receiving bottle is about 41 ml, the entire distillation process lasts for about 3 h to 4 h) At this time, the distillation was stopped, and the pH of the distillate was 5.0 to 6.0 at this time. The distillation process is shown in Figure 3. If the sample is distilled more than 85%, the pH value of the distillate was measured with a pH test paper, and if it was less than 5.0, the sample was discarded. Note. The distillate should be stored at room temperature and protected from light before analysis and analyzed within 48 h. Figure 3 Schematic diagram of sample distillation 7.3 Preparation of blank samples The test water was used instead of the sample, and the laboratory blank sample was prepared in the same manner as the sample preparation (7.2). Ready. 58 Analysis steps 8.1 Instrument Reference Conditions 8.1.1 Purge and trap thermal desorption reference conditions Purge gas. nitrogen (5.21) or argon (5.22); flow rate. 350 ml/min; purge time. about 10.0 min; Gas. argon (5.22); thermal desorption temperature. 130 ° C; thermal desorption time. 10 s (carrier gas flow rate of 35 ml/min) or 60 s (Carrier gas flow rate is 15 ml/min). 8.1.2 Chromatography and cleavage reference conditions a) packed column. 40 ° C; carrier gas flow rate. 35 ml/min; b) Capillary column. 93 ° C   min/5 ° C 97 ° C (105 s)   min/5.4 ° C 100 ° C (105 s); carrier gas flow Speed. 15 ml/min; c) Cracking temperature. 750 °C. 8.1.3 Cold atomic fluorescence mercury analyzer reference conditions Photomultiplier tube (PMT) negative high pressure. about 690 V; carrier gas flow rate. 35 ml/min; other according to the instrument operating instructions Book settings. 8.2 Calibration 8.2.1 Preparation of the standard series Pre-add 40 ml of water and 500 μl of acetic acid-sodium acetate buffer solution (5.12) in the sample bottle (6.8), and then separately Prepare at least 6 concentration points by adding an appropriate amount of mixed standard use solution II (5.18) and mixed standard use solution I (5.17). The standard series, target compound content is 0 pg, 5.00 pg, 10.0 pg, 20.0 pg, 50.0 pg, 100 pg (this For reference content), add 50 μl of sodium tetrapropylborate solution (5.11) to each vial, seal and react for 20 min; When using the ectopic purge and trap injection, add water to the full bottle before sealing and react for 20 min. 8.2.2 Establishment of calibration curve According to the instrument reference conditions (8.1), the standard series of solutions are determined in order from low content to high content. The target compound content (pg) in the series solution is the abscissa, and the calibration is established by the corresponding peak area or peak height as the ordinate. curve. 8.3 Sample determination Transfer all the sample (7.2) to the injection bottle (6.8), add 50 μl of sodium tetrapropylborate solution (5.11), press The sample was measured in the same operating procedure and instrumental analysis conditions as the calibration curve (8.2.2). 8.4 Blank test The laboratory blank sample (7.3) was measured in accordance with the same procedure and instrumental conditions as the sample measurement (8.3). 69 Calculation and representation of results 9.1 Qualitative analysis Qualitative according to the retention time of the target compound in the sample and the target compound in the standard series. For the standard chromatogram of 1.00 ng/L methylmercury and ethylmercury, see the instrument reference conditions (8.1) specified in this standard. Figure 4. 1-methylmercury; 2-ethylmercury; 3--divalent mercury. a, the column is a packed column; b, the column is a capillary column. Figure 4 Standard chromatogram of methylmercury and ethylmercury 9.2 Calculation of results The mass concentration of alkyl mercaptan in the sample, i (ng/L), is calculated according to formula (1).    (1) Where. i - the mass concentration of the target compound i in the sample, ng/L; Im - the content of the target compound i calculated from the calibration curve, pg; V--sample volume when the sample is distilled, ml; D--sample dilution factor. 79.3 Results When the measurement result is less than 1.00 ng/L, the two decimal places are retained; when the measurement result is greater than or equal to 1.00 ng/L, Keep three significant digits. 10 Precision and accuracy 10.1 Precision Six laboratories added blanks with concentrations of methylmercury and ethylmercury of 0.10 ng/L, 1.00 ng/L and 4.44 ng/L, respectively. The standard sample was tested repeatedly. the relative standard deviations in the methylmercury laboratory were 2.5%-6.0% and 1.3%-6.0%, respectively. And 1.1% to 3.9%; the relative standard deviations between laboratories are 10%, 12%, and 15%, respectively; the repeatability limit is 0.01 ng/L, 0.09 ng/L and 0.34 ng/L; reproducibility limits were 0.03 ng/L, 0.33 ng/L and 1.8 ng/L. Ethyl mercury in the laboratory The standard deviations were 1.3% to 10%, 0.9% to 6.9%, and 1.7% to 4.5%, respectively; the relative standard deviations between laboratories were 18%, 8.3%, and 9.6%; repeatability limits were 0.02 ng/L, 0.10 ng/L, and 0.33 ng/L; reproducibility was limited to 0.05 ng/L, 0.22 ng/L and 1.1 ng/L. For the method precision summary data, see Table A.1 in Appendix A. 10.2 Accuracy Surface water samples with a concentration of 0.10 ng/L to 0.22 ng/L and 1.00 ng/L for methyl mercury and ethyl mercury in six laboratories The product was subjected to 6 repeated measurements. the recoveries of methylmercury spiked were 81.7%~106% and 87.8%~112%, respectively; The final recoveries were 94.4% ± 16.6% and 95.2% ± 19.0%. The recoveries of ethyl mercury spiked were 76.0%~ 90.4% and 76.3% to 94.1%; the final recoveries were 84.0% ± 11.0% and 84.1% ± 12.4%. The concentration of methylmercury and ethylmercury in the six laboratories was 0.09 ng/L to 0.10 ng/L and 0.90 ng/L to 1.00 ng/L. The domestic sewage samples were subjected to 6 repeated measurements. the recoveries of methyl mercury spiked were in the range of 75.0% to 110%, respectively. 84.5%~111%; the final values of the spiked recovery were 96.2%±25.4% and 100%±22.2%, respectively. Ethyl mercury spike recovery The rate ranges from 70.2% to 91.8% and 74.9% to 90.9%, respectively. The final recoveries are 83.1%±15.2% and 83.9% ± 11.0%. The concentration of methylmercury and ethylmercury in the six laboratories was 0.09 ng/L to 0.10 ng/L and 0.90 ng/L to 1.00 ng/L. The industrial wastewater samples were subjected to 6 repeated measurements. the recoveries of methyl mercury spiked were in the range of 88.8% to 112%, respectively. 83.5%~111%; the final values of the spiked recovery were 101%±17.2% and 95.9%±21.4%, respectively. Ethyl mercury spike recovery The rate ranges from 71.0% to 78.7% and 71.2% to 90.0%, respectively. The final values of the spiked recovery are 75.2%±5.8% and 78.3% ± 13.0%. Six replicate measurements of seawater samples with methyl mercury and ethylmercury spiked at a concentration of 0.10 ng/L were performed in the laboratory. The recoveries of base mercury spiked ranged from 87.3% to 97.6%; the final recoveries of spiked standards were 91.5%±7.2%. Ethyl mercury plus standard The yield ranged from 76.7% to 90.2%; the final recovery of the spiked standard was 85.0% ± 10.0%. For the method accuracy summary data, see Table A.2 in Appendix A. 811 Quality Assurance and Quality Control 11.1 blank At least one laboratory blank should be made for every 20 samples or batches (< 20/batch), and the results should be lower than Method detection limit. 11.2 Calibration A calibration curve should be established before each sample analysis. The correlation coefficient of the curve is ≥0.996. The standard series solution of the intermediate concentration point of the curve is measured at least once a day during the measurement of the sample, and the measurement result is between the standard value and the standard value. The relative error should be within ±20%. Otherwise, a new calibration curve must be established. 11.3 Parallel double sample At least one parallel sample should be measured for every 20 samples or batches (< 20/batch), and the relative results of the measurements The deviation should be ≤ 20%. 11.4 Matrix addition At least one matrix spiked sample should be assayed for every 20 samples or batches (< 20/batch). Methylmercury plus standard The yield is controlled between 75% and 120%; the recovery rate of ethyl mercury plus standard is controlled between 70% and 120%. If not in scope, Matrix interference should be considered and the method of diluting the sample can be used to reduce interference. 12 Waste treatment The waste liquid generated in the experiment should be collected centrally, kept in a safe place, and properly marked, and entrusted with qualified units to carry out the work. Set. 13 Precautions 13.1 Sodium tetrapropylborate is toxic and should be quickly and promptly sealed when taken or added. Ineffective sodium tetrapropylborate solution Put it into a large beaker containing hydrochloric acid solution (5.8), heat and decompose the residue at 80 °C, and reduce the volume of the solution in the beaker by 1/2. At the time, collect the remaining waste acid solution and dispose of it in a unified manner. 13.2 Before derivatization, the Hg2 content of the sample must be less than 1 ng. Add 100 μl of mercury to an equal volume of water to the sample. The quasi-use liquid (5.20) is measured according to the same operation steps and instrument conditions as the sample measurement, and the peak height or peak area is recorded. Using this as a reference, it is judged whether or not Hg2 in the sample exceeds 1 ng. 13.3 During the sample distillation process, the volume of the distillate in all the retort should be observed to avoid excessive distillation of the sample. Distillation After the end, the connection line between the retort and the receiving bottle should be disconnected in time and the retort should be removed. 13.4 When the Hg2 is abnormally high during the analysis of the sample or the peak cannot be completed within the set time, an empty test shall be added. White sample to prevent analysis of subsequent samples. 13.5 All utensils used in the experiment (sampling bottles, distillation bottles, receiving bottles, injection bottles, Teflon tubes, etc.) should be in the nitrate Soak in acid solution (5.9) for at least 24 h and wash with water. The glass bottle is placed in a muffle furnace and fired at 400 ° C for 4 h. After cooling. 9 to be used. Distillation bottles, receiving bottles and pipelines made of Teflon should be blown on a clean bench with mercury-free dry air or nitrogen. Dry, then packaged in a clean double polyethylene bag, marked and stored for later use.

Appendix A

(informative appendix) Method precision and accuracy The method precision and accuracy summary data for this method are as follows. Table A.1 Precision Summary Table Compound name average value (ng/L) Relative standard in the experimental room Quasi-deviation range (%) Relative standard between laboratories Quasi-bias (%) Repetitive limit r (ng/L) Reproducibility limit R (ng/L) Methylmercury 0.10 2.5～6.0 10 0.01 0.03 0.99 1.3～6.0 12 0.09 0.33 4.34 1.1 to 3.9 15 0.34 1.8 Ethyl mercury 0.09 1.3～10 18 0.02 0.05 0.87 0.9～6.9 8.3 0.10 0.22 3.84 1.7 to 4.5 9.6 0.33 1.1 Table A.2 Accuracy Summary Table Compound name sample type Sample concentration (ng/L) Standard concentration (ng/L) Spike recovery range(%) P(%) PS (%) Scaling recovery rate P±2 S (%) Methylmercury Surface water 0.08~0.46 0.10～0.22 81.7～106 94.4 8.3 94.4±16.6 1.00 87.8～112 95.4 9.5 95.2±19.0 Domestic sewage 0.04～0.17 0.09～0.10 75.0～110 96.2 12.7 96.2±25.4 0.90~1.00 84.5～111 100 11.1 100±22.2 Industrial wastewater 0.05～0.26 0.09～0.10 88.8～112 101 8.6 101±17.2 0.90~1.00 83.5～111 95.9 10.7 95.9±21.4 Seawater 0.15 0.10 87.3～97.6 91.5 3.6 91.5±7.2 Ethyl mercury Surface water ND 0.10～0.22 76.0～90.4 84.0 5.5 84.0±11.0 1.00 76.3～94.1 83.1 6.2 84.1±12.4 Domestic sewage ND 0.09～0.10 70.2～91.8 83.1 7.6 83.1±15.2 0.90～1.00 74.9～90.9 83.9 5.5 83.9±11.0 Industrial wastewater ND 0.09～0.10 71.0～78.7 75.2 2.9 75.2±5.8 0.90~1.00 71.2～90.0 78.3 6.5 78.3±13.0 Seawater ND 0.10 76.7～90.2 85.0 5.0 85.5±10.0 Note. ND means not detected.

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