HJ 1067-2019Water quality--Determination of benzene and its analogies--Headspace / gas chromatography (English PDF)

6.1 Sample collection

Collect samples in accordance with the relevant regulations of HJ/T 91, HJ 91.1, HJ/T 164 and HJ 494.

Before sampling, measure the pH of the sample. According to the pH measurement result, add an appropriate amount of hydrochloric acid to the sampling bottle (5.1).

(4.5) and add 25 mg of ascorbic acid (4.4) to make the sample pH <= 2 after sampling. If the sample is added with hydrochloric acid solution If air bubbles are generated, re-sampling is required. The re-collected samples are stored without adding hydrochloric acid solution. The sample label must indicate that it is not acidified.

When collecting samples, allow the sample to overflow in the vial without leaving space on the liquid. Try to avoid or reduce the Exposed in the air. All samples were taken in duplicate.

Note. The sample bottle should be washed and dried with methanol (4.1) before sampling. It is not necessary to rinse the sample with the sample.

6.2 Collection of blank samples during the whole procedure

Bring the experimental water to the sampling site and follow the same procedure (6.1) as the sample collection to collect a blank sample of the entire procedure.

36.3 Sample preservation

After the samples are collected, they should be transported and stored refrigerated below 4 ° C, and the analysis should be completed within 14 days. Sample storage area should be non-volatile Organic matter interferes, the sample should be returned to room temperature before measurement.

Note. Non-acidified samples should be analyzed within 24 h.

6.4 Preparation of test specimens Add 3 g of sodium chloride (4.3) to the headspace bottle (5.6), add 10.0 ml of sample (6.3), and immediately seal Seal, shake well and test.

6.5 Preparation of laboratory blank samples Use experimental water to replace the sample, and follow the same steps as in the sample preparation (6.4) to prepare a laboratory blank sample.

Equipment.

7 Analysis steps

7.1 Instrument reference conditions

7.1.1 Headspace Sampler Reference Conditions Heating equilibrium temperature. 60 °C; Heating equilibration time. 30 min; Sample valve temperature. 100 °C; Transmission line temperature. 100 °C;

Injection volume. 1.0 ml (loop).

7.1.2 Gas chromatograph reference conditions Inlet temperature..200 ° C; Detector temperature. 250 ° C; Column heating program. 40 ° C (hold for 5min), at 5 ° C / min The temperature rises to 80 ° C (hold for 5 min); carrier gas flow rate. 2.0 ml/min; combustion gas flow rate. 30 ml/min; combustion support Air flow rate. 300 ml/min; makeup air flow rate. 25 ml/min; split ratio is 10. 1.

7.2 Establishment of working curve Add 3 g of sodium chloride (4.3) to the 7 headspace bottles (5.6), and then add 10.0 ml, 10.0 ml, 10.0 ml, 9.8 ml, 9.6 ml, 9.2 ml, and 8.8 ml water, then add 5.00 µl, 20.0 µl, 50.0 µl, 0.20 ml, 0.40 ml, 0.80 ml, and 1.2 ml standard use solutions (4.7), formulated into the target compound the mass concentrations are 0.050 mg/L, 0.200 mg/L, 0.500 mg/L, 2.00 mg/L, 4.00 mg/L, 8.00 mg/L, 12.0 mg/L standard series (this is the reference concentration, at least 5 non-zero concentration points can be selected to cover the sample concentration range), Immediately seal the headspace bottle, shake gently, and inject and analyze from low concentration to high concentration in accordance with the instrument reference conditions (7.1) Record the retention time and response values of the standard series of targets. Take the target compound concentration as the abscissa and its corresponding response value for the ordinate, create a working curve.

7.3 Sample determination the measurement of the sample (6.4) is performed under the same conditions as the establishment of the working curve (7.2).

Note. If the sample concentration exceeds the highest concentration point of the working curve, you need to re-sample from the unopened sample bottle, and then re-dilute the sample after dilution.

Preparation of 4 (6.4).

7.4 Laboratory blank test Follow the same procedure as for the sample measurement (7.3) to measure the laboratory blank sample (6.5).

8 Results calculation and representation

8.1 Qualitative analysis Qualitative based on the retention time of the target in the sample and the target in the standard series. Before sample analysis, when establishing retention the window t ± 3S. t is the average retention time of the target compound at each concentration level during calibration, and S is the concentration level at each initial calibration level Standard deviation of target compound retention time. During sample analysis, the target should peak within the retention time window.

When it is detected on column I (5.3) but cannot be confirmed, column II (5.4) can be used for auxiliary characterization. color the reference conditions for the determination of column II are the same as the reference conditions of the instrument (7.1). See Appendix B for the standard chromatograms of benzene series.

Under the measurement conditions specified in this standard, the standard reference chromatogram of benzene series is shown in Figure 1.

1-methanol; 2-benzene; 3-toluene; 4-ethylbenzene; 5-p-xylene; 6-m-xylene; 7-cumene; 8-o-xylene; 9-styrene.

Figure 1 Standard chromatogram of benzene series on column I (6000 µg/L)

8.2 Calculation of results the mass concentration (µg/L) of the target compound in the sample is calculated according to formula (1).

% 00% 00% 00% 00% 00% 00% 00 (1) in the formula. I-mass concentration of the target compound in the sample, µg/L;

i-mass concentration of target compound obtained from the working curve, µg/L;

D--The dilution factor of the sample.

58.3 Result representation

The number of digits after the decimal point in the measurement result is the same as the detection limit of the method. A maximum of 3 significant digits are retained.

9 Precision and accuracy

9.1 Precision

Six laboratories performed six replicates of benzene series uniformly mixed standard samples at concentration levels of 20 µg/L and 100 µg/L Re-assay. the relative standard deviations in the laboratory are 1.6% to 15% and 2.1% to 9.5%; the relative standard deviations between laboratories 8.2% ~ 12% and 2.7% ~ 5.6% respectively; repeatability limits r are 4 µg/L ~ 4 µg/L and 12 µg/L ~ 19 µg/L;

Reproducibility limits R are 6 µg/L to 8 µg/L and 14 µg/L to 23 µg/L, respectively.

1 laboratory performed standard mixtures of benzene series at 50 µg/L, 2000 µg/L and 10,000 µg/L Six repeated determinations were performed. the relative standard deviations in the laboratory were. 5.6% to 9.2%, 2.9% to 7.8%, and 1.9% to 2.6%.

9.2 Accuracy

Six laboratories performed six repeated spiking analyses on surface water samples with a spiked concentration of 100 µg/L. average spiking the standard recovery range is 85.9% ~ 122%; the final recovery range of standard addition is 102% ± 13.0% ~ 106% ± 11.0%.

One laboratory performed 6 repeated spiking analyses on groundwater samples spiked at 500 µg/L. average spiking the standard recovery range is 78.4% ~ 91.6%; the final recovery range of standard addition is 84.6% ± 7.8% ~ 88.4% ± 6.0%.

One laboratory performed 6 repeated spiking analyses on domestic sewage samples with a spiked concentration of 1000 µg/L.

The average spike recovery rate range is 76.1% ~ 92.6%; the final spike recovery rate range is 80.1% ± 7.9% ~ 87.6% ± 5.7%.

1 laboratory has ethylbenzene concentration of 9.5 µg/L, para-xylene concentration of 5.3 µg/L, and meta-xylene concentration of Six samples of industrial waste water with 11.6 µg/L, ortho-xylene concentration of 19.4 µg/L, and styrene concentration of 19.4 µg/L were performed 6 times.

Repeated spiking analysis and determination, spiking concentration is 6000 µg/L. average spiking recovery range is 84.5% ~ 103%;

The final yield range was 87.0% ± 5.9% ~ 96.7% ± 8.8%.

For precision and accuracy results, see Tables C.1 to C.4 in Appendix C.

10 Quality Assurance and Quality Control

10.1 Blank test

Every 20 samples or each batch of samples (7 Appendix A (Normative appendix) Detection limit and lower detection limit of the target compound

Table A.1 shows the detection limit and the lower detection limit of the method when the sampling volume is 10.0 ml.

Table A.1 Detection limits and determination limits for target compounds

Substance name detection limit (µg/L) Lower detection limit (µg/L) Benzene 2 8 Toluene 2 8 Ethylbenzene 2 8 P-xylene 2 8 M-xylene 2 8 Cumene 3 12 O-xylene 2 8 Styrene 3 12

8 Appendix B

(Informative appendix) Auxiliary qualitative reference chromatogram refer to Figure B.1 for the reference chromatogram of the separation of benzenes using column II (5.4) according to the instrument reference conditions (7.1).

1-methanol; 2-benzene; 3-toluene; 4-ethylbenzene; 5-p-, m-xylene; 6-o-xylene, styrene; 7-cumene.

Figure B.1 Reference chromatogram of benzene series (column II auxiliary characterization) (6000 µg/L)

min5 10 15 20 25 30

FID1 A, front signal (pyridine 2017 \\ pyridine double column test-DB624.2017-07-27 11-31-47 \\ 17072707.D)

9 Appendix C

(Informative appendix) Method precision and accuracy Tables C.1 to C.4 give the precision and accuracy of the methods, respectively.

Table C.1 Precision of 6 laboratory methods

Substance name Benzene ethylbenzene p-xylene meta-xylene cumene o-xylene styrene 20 µg/L Measured average (Mg/L) 20 19 19 19 20 19 20 19 Relative in the laboratory standard deviation(%) 3.0 ~ 13 4.1 ~ 15 4.1 ~ 9.4 4.9 ~ 12 4.4 ~ 12 4.1 ~ 15 3.6 ~ 12 1.6 ~ 14 Interlaboratory standard deviation(%) 8.2 9.8 11 11 12 11 9.5 8.2 Repeatability limit r (Mg/L) Reproducibility limit R (Mg/L) 100 µg/L Measured average (Mg/L) 97 96 96 94 96 96 96 96 Relative in the laboratory standard deviation(%) 2.1 ~ 6.1 3.0 ~ 6.0 2.9 ~ 8.9 4.5 ~ 7.7 2.6 ~ 7.2 4.4 ~ 9.5 3.1 ~ 6.4 3.8 ~ 6.3 Interlaboratory standard deviation(%) 3.9 3.8 4.4 5.3 4.2 5.6 3.1 2.7 Repeatability limit r (Mg/L) 12 14 15 15 14 19 14 14 Reproducibility limit R (Mg/L) 16 16 18 19 17 23 15 14

Table C.2 Precision of 1 laboratory method

Substance name Benzene ethylbenzene p-xylene meta-xylene cumene o-xylene styrene 50 µg/L Measured average (Mg/L) 52 55 51 53 51 51 48 49 Relative in the laboratory standard deviation(%) 6.3 5.6 8.5 8.4 7.2 9.2 7.7 6.0 2000 µg/L Measured average (Mg/L) 2.02 × 103 2.04 × 103 1.91 × 103 2.07 × 103 2.07 × 103 2.08 × 103 2.06 × 103 2.05 × 103 Relative in the laboratory standard deviation(%) 2.9 4.8 7.0 7.4 7.2 7.8 6.0 4.7 10000 µg/L Measured average (Mg/L) 9.95 × 103 9.96 × 103 9.99 × 103 10.0 × 103 9.99 × 103 9.99 × 103 9.99 × 103 10.0 × 103 Relative in the laboratory standard deviation(%) 2.6 2.4 2.1 2.1 2.1 1.9 2.1 2.5

Table C.3 Accuracy of 6 laboratory methods

Sample type compounds Sample concentration (Mg/L) Spiked concentration (Mg/L) Spike recovery range(%) Final spike recovery P ± 2 PS (%) Surface water Benzene 0 100 85.9 ~ 119 105 ± 24.2 Toluene 0 100 92.5 ~ 120 105 ± 20.4 Ethylbenzene 0 100 94.2 ~ 120 105 ± 19.6 P-xylene 0 100 95.7 ~ 121 105 ± 19.8 M-xylene 0 100 90.8 ~ 122 104 ± 21.4 Cumene 0 100 88.4 ~ 122 103 ± 26.8 O-xylene 0 100 94.2 ~ 111 102 ± 13.0 Styrene 0 100 100 ~ 113 106 ± 11.0

Table C.4 Accuracy of 1 laboratory method

Sample type compounds Sample concentration (Mg/L) Spiked concentration (Mg/L) Spike recovery range(%) Final spike recovery P ± 2 PS (%) groundwater Benzene 0 500 84.4 ~ 91.6 88.4 ± 6.0 Toluene 0 500 81.6 ~ 89.4 86.6 ± 5.4 Ethylbenzene 0 500 79.6 ~ 88.8 85.5 ± 6.7 Paraxylene 0 500 79.4 ~ 88.8 85.4 ± 7.0 M-xylene 0 500 79.6 ~ 88.4 85.3 ± 6.6 Cumene 0 500 78.4 ~ 88.6 84.6 ± 7.8 O-xylene 0 500 80.8 ~ 89.2 86.1 ± 6.1 Styrene 0 500 82.2 ~ 89.8 86.8 ± 5.6 domestic sewage Benzene 0 1000 80.2 ~ 84.3 82.2 ± 2.8 Toluene 0 1000 78.3 ~ 85.4 81.1 ± 5.0 Ethylbenzene 0 1000 77.0 ~ 86.2 80.3 ± 6.9 Paraxylene 0 1000 77.6 ~ 87.2 81.0 ± 7.2 M-xylene 0 1000 77.6 ~ 87.1 81.0 ± 7.2 Cumene 0 1000 76.1 ~ 86.6 80.1 ± 7.8 O-xylene 0 1000 80.6 ~ 89.0 83.5 ± 6.4 Styrene 0 1000 85.2 ~ 92.6 87.6 ± 5.7 Continued Sample type compounds Sample concentration (Mg/L) Spiked concentration (Mg/L) Spike recovery range(%) Final spike recovery P ± 2 PS (%) Industrial waste Benzene 0 6000 91.4 ~ 103 96.7 ± 8.8 Toluene 0 6000 90.3 ~ 102 95.1 ± 8.6 Ethylbenzene 9.5 6000 88.2 ~ 98.2 91.6 ± 7.8 Paraxylene 5.3 6000 88.0 ~ 97.8 91.3 ± 7.6 M-xylene 11.6 6000 88.0 ~ 98.4 91.4 ± 7.9 Cumene 0 6000 84.5 ~ 92.5 87.0 ± 5.8 O-xylene 19.4 6000 90.0 ~ 98.4 92.5 ± 6.6 Styrene 19.4 6000 92.4 ~ 101 95.0 ± 6.4