HJ 1070-2019Water quality--Determination of 15 chlorinated herbicides--Gas chromatography (English PDF)

4.17 Standard stock solution of chlorinated herbicides. rho = 100 mg/L

Commercially available certified standard solutions can be purchased directly. The standard solution after opening is sealed and stored under frozen and protected from light, effective 1 year. Alternatively, the standard chlorinated herbicide can be placed in a desiccator containing silica gel for 48 h, then weighed with acetone (4.7) Formulated for solvents.

4.18 Mixed standard chlorinated herbicide use solution. rho = 10.0 mg/L

Pipette 10.00 ml of standard chloro herbicide stock solution (4.17) into a 100 ml volumetric flask, dilute with acetone (4.7) and Make up to the mark. The standard use solution is refrigerated at 4 ° C and stored in the dark, and the shelf life is two months. Should be returned to room temperature during use, and Shake well.

4.19 Solid-phase extraction column. 500 mg/6 ml, packed with divinylbenzene and N-vinylpyrrolidone copolymer or equivalent Extraction column.

4.20 Silica gel column. 500 mg/6 ml, packed with chromatography silica gel of 40 µm ~ 75 µm.

4.21 Nitrogen. Purity >=99.999%.

6.1 Sample collection and storage

Samples were collected in accordance with the requirements of HJ 91.1, HJ/T 91, HJ/T 164, HJ 442 and GB 17378.3.

Immediately after the sample was collected, adjust the pH <= 2 with hydrochloric acid solution (4.13), refrigerate at 4 ° C and store in the dark, and extract within 7 days.

The extract was analyzed within 30 days.

6.2 Preparation of test specimens

6.2.1 Hydrolysis

Measure 500 ml of sample into a separatory funnel, adjust the pH of the solution to >=12 with sodium hydroxide solution (4.12), and let stand for 1 h.

The sample volume is recorded as V.

Note. For high concentration samples, reduce the sample size. For samples containing only phenoxycarboxylic acid herbicides, no hydrolysis is required.

6.2.2 Extraction

6.2.2.1 Liquid-liquid extraction method

Clean samples such as surface water and groundwater can be directly extracted without purification. For samples with complex matrices, the sample (6.2.1) is decontaminated.

Purification. Add 30 ml of dichloromethane (4.6) to the hydrolyzed sample (6.2.1), shake and deflate, and shake to extract After 15 minutes, let stand for 15 minutes. After the two phases are separated, the lower organic phase is discarded. Add another 30 ml of dichloromethane and repeat the extraction.

Next, the lower organic phase was discarded.

Extraction. Use phosphoric acid (4.1) to adjust the hydrolyzed sample (6.2.1) or purified sample to pH <= 2 and add 10 g of chlorinated Sodium (4.4), shake to dissolve. Add 30 ml of dichloromethane (4.6), shake and deflate, shake for 15 min, and let stand 15 minutes, after the two phases were separated, the organic phase dehydrated by anhydrous sodium sulfate was collected in a graduated concentration flask (5.6). Reuse 30 ml of dichloromethane were repeatedly extracted twice. Combine the organic phases dehydrated with anhydrous sodium sulfate and concentrate with a concentration device (5.3) Nearly dry. Dissolve in 5 ml of acetone (4.7) and wait for derivatization.

6.2.2.2 Solid-phase extraction

Column activation. Place the solid-phase extraction column (4.19) on the solid-phase extraction device (5.5). 10 ml of dichloromethane (4.6), 10 ml of methanol (4.8) is passed through the solid-phase extraction column at a rate of about 5 ml/min.

Add 20 ml of water. When about 2 ml of water remain, close the valve.

Enrichment. The pH of the hydrolyzed sample (6.2.1) was adjusted to <= 2 with phosphoric acid (4.1). Pass the sample at a flow rate of 10 ml/min.

Pass the activated solid phase extraction column. After the sample is completely enriched, continue to pump for 10 min or purge with nitrogen (4.21) to make the extraction.

The column was dried. Then add 20 ml of methanol (4.8) to elute and collect the eluate into a graduated concentration flask (5.6). With concentration device (5.3) Concentrate to near dryness and dissolve in 5 ml of acetone (4.7) until derivatized.

6.2.3 Derivation

Add 30 µl potassium carbonate solution (4.14) to the extraction solution (6.2.2.1 or 6.2.2.2) to be derivatized, mix well and add 200 µl pentafluorobenzyl bromide solution (4.16), sealed with a stopper and derivatized in a water bath at 60 ° C ± 2 ° C for more than 3 h.

After derivatization, the reaction solution was concentrated to 0.5 ml with a concentration device (5.3), and the volume was adjusted with a toluene-n-hexane mixed solvent (4.10).

To 2 ml.

6.2.4 Purification after derivation

The silica gel column (4.20) was packed with 0.5 g of anhydrous sodium sulfate (4.3). Rinse the silica gel column with 5 ml of n-hexane (4.5).

Add the sample to a silica gel column, rinse with 10 ml toluene-n-hexane mixed solvent (4.10), and discard the eluent. With 8 ml plus the hexane-toluene mixed solvent (4.11) was used for elution. The entire eluate was received in a 10 ml stopper colorimetric tube, and the volume was adjusted with n-hexane.

To the mark, to be tested.

6.3 Preparation of blank samples

Use experimental water to replace the sample, and follow the same steps as in the sample preparation (6.2) to prepare a laboratory blank sample.

Equipment.

7.1 Chromatographic Reference Conditions

Inlet temperature. 250 ° C, splitless injection.

Detector. ECD.

Detector temperature. 300 ° C.

Heating program. keep the initial temperature at 80 ° C for 2 minutes, raise it to 170 ° C at 30 ° C/min, keep it for 5 minutes, and then keep it at 10 ° C/min the temperature was raised to.200 ° C and held for 2 minutes, and then raised to 300 ° C at 10 ° C/min for 5 minutes.

Carrier gas. nitrogen (4.2.1); flow rate. 1.0 ml/min.

Makeup gas flow. 30 ml/min.

Injection volume. 1.0 µl.

7.2 Establishment of working curve

Take 20.0 µl, 50.0 µl, 100 µl, 500 µl, and 1000 µl of the standard use solution (4.18) in the graduated concentration bottle (5.6) , Dilute to 5 ml with acetone, and prepare each target compound content as 0.50 µg, 1.00 µg, 2.50 µg, 5.00 µg and 10.0 µg (This is the reference content) standard series.

Follow the same steps as 6.2.3 and 6.2.4 to perform derivatization and purification treatment, and inject samples from low concentration to high concentration in order.

Using the target compound content as the abscissa and the corresponding peak area as the ordinate, a working curve was established.

Under the chromatographic reference conditions (7.1) specified in this standard, the standard gas chromatograms of 15 chlorinated herbicides are shown in Figure 1.

1-2,2-dichloropropionic acid; 2-3,5-dichlorobenzoic acid; 3-2- (4-chloro-2-methylphenoxy) propionic acid; 4-3,6-dichloro -2-methoxybenzoic acid; 5 2-methyl-4-chlorophenoxyacetic acid; 6-2,4-dipropionic acid; 7-2,4-dichlorophenoxyacetic acid; 8-2,4,5-trichlorophenoxyacetic acid; 9 -Pentachlorophenol; 10-2,4,5-Labelic acid; 11-3-amino-2,5-dichlorobenzoic acid; 12-2,4-dichlorophenoxybutyric acid; 13-4-amino-3,5,6 -Trichloropyridinecarboxylic acid; 14-Trifluorocarboxenol; 15-tetrachloroterephthalic acid.

Figure 1 Reference gas chromatograms of 15 chlorinated herbicide derivatives (rho = 1000 µg/L)

7.3 Sample determination

Test the sample (6.2.4) under the same conditions as the establishment of the working curve (7.2). If the test concentration exceeds when the working curve concentration range is obtained, the sample is diluted to the working curve concentration range, and the dilution factor is recorded as D.

7.4 Blank test

The blank sample (6.3) was measured under the same conditions as the sample measurement (7.3).

8.1 Qualitative analysis

Characterized by the retention time of each target compound according to the standard chromatogram. Gas chromatography-mass spectrometry (GC-MS) Qualitative confirmation.

8.2 Calculation of results

The mass concentration of the target compound in the sample is calculated according to formula (1).

Where. rhoi--mass concentration of target compound i in the sample, µg/L mi--the content of the target compound i obtained from the working curve, µg;

V--sample volume, L;

D--Dilution multiple.

8.3 Representation of results

The number of digits after the decimal point of the measurement result is kept consistent with the detection limit of the method, and a maximum of three significant digits are retained.

9.1 Precision

9.1.1 Liquid-liquid extraction

Six laboratories performed 6 replicates of blank spiked samples with chlorinated herbicide concentrations of 0.500 µg/L and 10.0 µg/L Re-assay. the relative standard deviations in the laboratory were 1.6% to 9.5% and 0.9% to 7.8%; the relative standard deviations between laboratories 2.1% to 5.8% and 1.6% to 4.5%, respectively; repeatability limits are 0.02 to 0.08 µg/L and 0.14 to 0.74 µg/L, respectively;

The performance limits were 0.04 to 0.14 µg/L and 0.54 to 1.3 µg/L, respectively.

Six laboratories conducted 6 spiked samples of surface water with chlorinated herbicide concentrations of 0.500 µg/L and 10.0 µg/L Repeated determination. the relative standard deviations in the laboratory were 2.0% to 13% and 2.0% to 8.8%; the relative standard deviations between laboratories the differences are 1.6% to 5.4% and 1.2% to 3.5%, respectively; the repeatability limits are 0.02 to 0.06 µg/L and 0.50 to 0.54 µg/L, respectively;

Reproducibility limits are 0.04 to 0.10 µg/L and 0.38 to 1.1 µg/L, respectively.

Six laboratories conducted six replicates of domestic sewage samples containing chlorinated herbicides at 1.00 µg/L and 18.0 µg/L Re-assay. the relative standard deviations in the laboratory are 4.4% -18% and 2.6% -10%, respectively; the relative standard deviations between laboratories 3.1% to 7.7% and 1.3% to 5.3%, respectively; the repeatability limits are 0.02 to 0.10 µg/L and 0.28 to 1.0 µg/L, respectively;

The performance limits were 0.12 ~ 0.24 µg/L and 0.82 ~ 2.8 µg/L, respectively.

Six laboratories carry out spiked samples of uniform industrial wastewater containing chlorinated herbicides at 1.00 µg/L and 18.0 µg/L Six repeated determinations. the relative standard deviations in the laboratory were 3.8% to 19% and 2.7% to 11%, respectively;

Standard deviations are 3.5% to 7.4% and 1.2% to 4.5%, respectively; repeatability limits are 0.04 to 0.12 µg/L and 0.28 to 1.0 µg/L; the reproducibility limits are 0.12 ~ 0.24 µg/L and 0.96 ~ 2.4 µg/L, respectively.

Six laboratories performed six replicates of seawater spiked samples containing chlorinated herbicides at 1.00 µg/L and 18.0 µg/L Repeat determination. the relative standard deviations in the laboratory are 3.9% to 15% and 2.6% to 11%, respectively;

0.8% to 5.6% and 1.5% to 4.0%, respectively; the repeatability limits are 0.04 to 0.10 µg/L and 0.32 to 1.1 µg/L, respectively;

The performance limits were 0.08 to 0.16 µg/L and 1.0 to 2.2 µg/L, respectively.

9.1.2 Solid Phase Extraction

Six laboratories performed 6 blank spiked samples with chlorinated herbicide concentrations of 0.500 µg/L and 10.0 µg/L Repeated determination. the relative standard deviations in the laboratory were 2.5% to 9.2% and 0.8% to 2.3%; the relative standard deviations between laboratories the differences are 14% to 27% and 1.8% to 4.1%, respectively; the repeatability limits are 0.02 to 0.04 µg/L and 0.04 to 0.16 µg/L, respectively;

Reproducibility limits are 0.20 to 0.36 µg/L and 0.52 to 1.2 µg/L, respectively.

Six laboratories performed spiked samples of surface water with chlorinated herbicide concentrations of 0.500 µg/L and 10.0 µg/L. 6 Repeated determinations. Relative standard deviations in the laboratory are 4.7% to 19% and 2.4% to 11%, respectively;

The deviations are 7.5% to 16% and 2.9% to 11%, respectively; the repeatability limits are 0.02 to 0.06 µg/L and 0.20 to 0.70 µg/L, respectively;

Reproducibility limits are 0.12 to 0.24 µg/L and 0.92 to 3.0 µg/L, respectively.

9.2 Accuracy

9.2.1 Liquid-liquid extraction

Six laboratories carried out spiking recovery measurements on surface water samples containing chlorinated herbicides, and the spiking concentrations were 0.500 µg/L and 10.0 µg/L. Spike recovery rates are 72% to 102% and 79% to 102%, respectively. Final recovery rates They were 81% ± 10% ~ 89% ± 10% and 86% ± 9% ~ 92% ± 9%.

Six laboratories conducted spiking analysis on samples of domestic sewage, industrial wastewater and seawater containing chlorinated herbicides.

The standard concentrations were 1.00 µg/L and 18.0 µg/L, respectively. Spike recovery rates were 63% to 92% and 78% to 94%, respectively.

The final yields were 67% ± 18% ~ 88% ± 15% and 60% ± 15% ~ 94% ± 10%.

9.2.2 Solid Phase Extraction

Six laboratories carried out spiking analysis on surface water samples containing chlorinated herbicides, and the spiking concentrations were 0.500 µg/L and 10.0 µg/L. Spike recovery rates are 79% ~ 102% and 81% ~ 102%, respectively.

87% ± 6% ~ 93% ± 9% and 87% ± 4% ~ 94% ± 9%, respectively.

For precision and accuracy results, see Appendix B.

10.1 Blank test

For each batch of samples, at least one blank sample is measured under the same analysis conditions as the sample. The blank measurement value should be below the detection limit.

10.2 Calibration

Make a working curve with at least 5 concentration points (excluding zero concentration points). The linear regression coefficient of the working curve should be large at 0.995. Otherwise, find the cause or redraw the working curve.

Every 20 samples or each batch (less than 20 samples/batch), an intermediate concentration test should be performed and the intermediate concentration determined the relative error between the value and the concentration value at this point should be within ± 20%, otherwise a new working curve should be established.

10.3 Parallel samples

Each batch of samples should be measured by 10% parallel samples, and the relative deviation of parallel samples should be within 30%.

10.4 Matrix Spiking

Each batch of samples should be at least one matrix spiked sample, and the recovery rate should be between 60% and 120%.