HJ 921-2017Soil and sediment--Determination of organochlorine pesticides--Gas chromatography (English PDF)

5.2 Column

5.2.1 Column 1. Column length 30 m, inner diameter 0.32 mm, film thickness 0.25 µm, stationary phase 5% polydiphenylsiloxane and 95% polydimethylsiloxane, or other equivalent column.

5.2.2 Column 2. Column length 30 m, inner diameter 0.32 mm, film thickness 0.25 µm, stationary phase 14% Polynyl cyanopropyl silicone Alkane and 86% polydimethylsiloxane, or other equivalent column.

5.3 Extraction device. microwave extraction device, Soxhlet extraction device, pressurized fluid extraction device or a device with a considerable function, no grease lubricant is allowed on all interfaces.

5.4 Concentration device. Nitrogen blowing instrument, rotary evaporator, KD concentrator or equipment with a considerable function.

5.5 Sampling Bottles. Wide-mouth brown glass bottles or Teflon-lined screw-on glass bottles.

5.6 general laboratory equipment and equipment.

6.1 Sample Collection and Storage

Soil samples were collected and stored according to the relevant requirements of HJ/T 166, and samples of marine sediments were related according to GB 17378.3 Requirements for collection and preservation, surface water sediment samples collected according to HJ/T 91 and HJ 494 requirements. Samples are saved in advance Clean the clean bottle (5.5), as soon as possible back to the laboratory analysis, the transport process should be sealed dark. If temporarily unable to analyze, it should be refrigerated at below 4 °C for 14 days. Sample extract (6.4.1) 4 °C below the dark storage, preservation the time is 40 days.

6.2 Sample Preparation

Remove foreign matter (stones, leaves, etc.) from the sample and weigh two portions of sample at about 10 g (to the nearest 0.01 g). Soil samples A product for the determination of dry matter content; the other by adding an appropriate amount of anhydrous sodium sulfate (4.4), grinding homogenized into sand-like dehydration;

If fruit is extracted by pressurized fluid extraction, it is dehydrated with diatomaceous earth (4.11). One sample of sediment is used to determine the moisture content and the other A reference soil sample is dehydrated.

6.3 Determination of moisture

Determination of dry matter content of soil samples in accordance with HJ 613 implementation, determination of sediment moisture content in accordance with GB 17378.5 carried out.

6.4 Sample Preparation

6.4.1 Extraction

6.4.1.1 Microwave extraction

The sample (6.2) all transferred to the extraction tank, adding 30 ml of acetone - n-hexane mixed solvent I (4.5), set the extraction the temperature was 110 °C, microwave extraction 10 min. The extract is collected after centrifugation or filtration.

6.4.1.2 Soxhlet extraction

The sample (6.2) was transferred to the Soxhlet extractor paper sleeve, 100 ml acetone-n-hexane mixed solvent (I 4.5) Extraction 16 h ~ 18 h, reflux rate of about 3 times/h ~ 4 times/h. The extract is collected after centrifugation or filtration.

6.4.1.3 Pressurized fluid extraction

HJ 783 in accordance with the requirements of the extraction.

Note. Other equivalent extraction methods may be used if verified.

6.4.2 Dehydration

Place a layer of glass wool or glass fiber filter (4.12) on the glass funnel, add about 5 g of anhydrous sodium sulfate (4.4) and then the extract (6.4.1) was directly filtered through a funnel to the concentration device (5.4), and then about 5 ml ~ 10 ml acetone - n-hexane Solvent I (4.5) The container containing the extract was thoroughly washed and filtered through a funnel to the above concentrator.

6.4.3 Concentration

After the dehydration at 45 °C below the extract (6.4.2) concentrated to 1 ml, to be purified.

To replace the solvent system, the extract was concentrated to 1.5 ml ~ 2.0 ml, with 5 ml ~ 10 ml of n-hexane (4.1) Replacement, and then concentrated extract to 1 ml, to be purified.

6.4.4 Purification

The magnesium silicate solid phase extraction column (4.9) was washed with about 8 ml of n-hexane (4.1), and the magnesium silicate solid phase extraction column adsorbent Surface infiltration. Pipette the concentrated extract (6.4.3) onto a magnesium silicate solid phase extraction cartridge and leave for 1 min Effluent. Add 2 ml of acetone-n-hexane mixed solvent II (4.6) and stay for 1 min, with 10 ml small concentrated tube to receive wash After degreasing, continue to wash the cartridge with acetone-n-hexane mixed solvent II (4.6) until the volume of the eluate received is 10 ml.

Note. If verified, other equivalent methods can also be used to purify. See Appendix C.

6.4.5 Concentrated volume

The purified eluate (6.4.4) according to the 6.4.3 step concentration and volume to 1.0 ml, and then transferred to 2 ml sample vial, to be analyzed.

6.5 Blank sample preparation

A blank sample was prepared according to the same procedure as Sample Preparation (6.4), replacing the actual sample with quartz sand (4.10).

7.1 GC reference conditions

Inlet temperature. 220 °C;

Injection mode. splitless injection to 0.75min after opening shunt, split outlet flow of 60ml/min;

Carrier gas. high purity nitrogen (4.13), 2.0 ml/min, constant current;

Makeup gas. high purity nitrogen (4.13), 20 ml/min;

Column temperature program. The initial temperature of 100 °C, 15 °C/min heating to 220 °C, holding 5 min, at 15 °C/min Warming up to 260 °C for 20 min;

Detector temperature. 280 °C;

Injection volume. 1.0 µl.

7.2 Calibration

7.2.1 The establishment of the standard curve Were appropriate amount of organochlorine pesticide standard solution (4.8), diluted with n-hexane (4.1), the preparation of standard series, the concentrations of organochlorine pesticides were 5.0 µg/L, 10.0 µg/L, 20.0 µg/L, 50.0 µg/L, 100 µg/L,.200 µg/L and 500 µg/L (this is the reference concentration).

According to the instrument conditions (7.1) from low concentration to high concentration in order to standard series of solution injection, detection, record the target Retention time, peak height or peak area. The concentration of the target in a standard series of solutions is taken as abscissa, with its corresponding peak height or peak Area for the vertical axis, the establishment of a standard curve.

7.2.2 Standard sample chromatogram

Under the recommended instrument reference conditions, the chromatograms for target 1 and 2 are shown in Figure 1 and Figure 2, respectively.

1.alpha - BHC; 2. Hexachlorobenzene; 3.gamma - BHC; 4.beta - BHC; 5.delta - BHC; 6. Endosulfan I; 7. Aldrin; 8. Endosulfan II; 9. Epichlorohydrin;

10. Epoxy heptachlor; 11. o, p'-Drip; 12. gamma-Chlordane; 13. alpha-Chlordane; 14. Trans- Iraq; 16.o, p'- droplet;

Dieldrin; 18. Endrin; 19. o, p'-DDT; 20. p, p'-drops; 21. cis- nonachlorohydrochloride; 22. p, p'- DDT; Mirex Fig.1 Reference GC chromatograms of 23 organochlorine pesticide standard samples (column 1, rho = 100 µg/L) 1. Hexachlorobenzene; 2.alpha - BHC; 3. gamma - BHC; 4. Endosulfan I; 5. Aldrin; 6. beta - BHC; 7. delta - BHC; 8. Endosulfan II; 9. Epichlorohydrin;

10. Epoxy heptachlor; 11. o, p'-Drip; 12. gamma-Chlordane; 13. alpha-Chlordane; 14. Trans- Iraq; 16. Dieldrin; 17. o, p'-Drip; 18. Endrin; 19. o, p'-DDT; 20. p, p'-drip; 21. cis-nonachloro; 22. p, p'- DDT; Mirex

Figure 2 Reference gas chromatogram of 23 organochlorine pesticide standard samples (column 2, rho = 100 µg/L)

7.3 Determination of the sample

The determination of sample (6.4) is carried out according to the same instrument analysis conditions as established in the standard curve (7.2.1).

7.4 Determination of blank sample

The blank sample (6.5) was measured according to the same instrument analysis conditions as the sample measurement (7.3).

8.1 Qualitative analysis

According to the retention time of the target qualitative. Before sample analysis, you should establish a retention time window t+/-3S, t standard within 72h Column solution, the average retention time of a target, S standard solution of a standard solution of the average retention time of a standard deviation difference. When analyzing samples, the target retention time should be within the retention window.

When the analysis of the target on the column is detected, it is necessary to use a different polarity of the column to help qualitative. The target is double when the column is detected, as detected, otherwise not detected.

8.2 Quantitative analysis

According to the established standard curve (7.2.1), according to the target peak area or peak height, the use of external standard method.

8.3 Results Calculation

8.3.1 Calculation of soil sample results

The target soil content omega1 (µg/kg), calculated according to equation (1).

Where. omega1 - soil samples in the target content, µg/kg;

rho - calculated from the standard curve of the sample mass concentration of the target, µg/L;

V-- sample volume, ml;

m - Weigh the quality of the sample, g;

wdm - dry matter content in the sample,%.

8.3.2 Calculation of Sediment Sample Results

Target sediment content omega2 (µg/kg), calculated according to equation (2).

Where. omega2 - sediment sample target content, µg/kg;

rho - calculated from the standard curve of the sample mass concentration of the target, µg/L;

V-- sample volume, ml;

H 2O

m - Weigh the quality of the sample, g;

wH2O - moisture content of the sample,%.

8.4 Results indicated

When the test result is less than 1.00 µg/kg, the result is kept at the second decimal place. When the test result is greater than or equal to 1.00 µg/kg when the result holds three significant figures.

9.1 Precision

Six laboratories performed a series of six samples of quartz sand spiked at concentrations of 2.00 µg/kg, 20.0 µg/kg and 80.0 µg/kg, respectively the relative standard deviations in the laboratory ranged from 2.1% to 10%, from 1.5% to 7.7% and from 0.47% to 5.7%, respectively.

The relative standard deviations in the laboratory ranged from 4.7% to 15%, 1.3% to 8.5%, and 0.90% to 3.6%, respectively. The repeatability limits Were 0.27 µg/kg ~ 0.42 µg/kg, 1.9 µg/kg ~ 2.8 µg/kg and 3.7 µg/kg ~ 8.8 µg/kg respectively. The reproducibility limits were 0.41 µg/kg to 0.80 µg/kg, 2.0 µg/kg to 4.3 µg/kg, and 4.0 µg/kg to 10.3 µg/kg. See Appendix B.

9.2 Accuracy

Six laboratories measured quartz spiked samples at spiking levels of 2.00 µg/kg, 20.0 µg/kg and 80.0 µg/kg, respectively, the spiked recoveries ranged from 77.0% to 116%, from 73.6% to 105% and from 92.0% to 105%, respectively. The final spike recoveries were 84.9% ± 25.4% -102% ± 18.8%, 77.5 ± 13.2% ± 96.4% ± 11.2%, 94.4 ± 4.8% ± 104% ± 2.0%. plus Sandy soils with a standard concentration of 20.0 µg/kg and six sediment samples from Taihu Lake were measured repeatedly for 6 replicates. The spiked recoveries ranged from 60.5% -108% and 58.5% -119% respectively, and the final recoveries of the spiked samples were 67.4% ± 9.2% -108% ± 4.2% and 68.1% ± 19.6% ~ 109% ± 34.4%. See Appendix B.

10.1 Blank experiment

Analyze at least one laboratory blank every 20 samples or batches (less than 20 samples/batch) for a measure of the target should be below the detection limit of the method.

10.2 Standard curve

The correlation coefficient of the standard curve is >=0.995.

For each 20 samples or batches (less than 20 samples/batches), a standard curve midpoint concentration solution should be analyzed, which measures the relative deviation of the result from the initial curve at this point should be <=20%. Otherwise, the standard curve should be redrawn.

10.3 Determination of parallel samples

Analyze at least one parallel sample per 20 samples or batches (less than 20 samples/batch), and determine the results of a single parallel sample the relative deviation should be less than 20%.

10.4 Blank spiked sample determination

Analyze at least one blank, spiked sample every 20 samples or batches (less than 20 samples/batch) with a recovery of 75% ~ Between 105%.

10.5 Substrate spike determination

Analyze at least one spiked sample every 20 samples or batches (less than 20 samples/batch) at the spiked concentration of the original sample Degree of 1 to 5 times, soil, sediment spiked sample recovery rate should be between 60% to 120%.

10.6 Instrument Performance Check

The chromatographic system should be checked before or every 24 h. Inject 1.0 µl of endrin and mix p, p'-DDT Standard solution (4.14), determine the degradation rate, according to formula (3) ~ formula (5) calculation. If in addition to the above compounds detected in addition, the detection of endrin,, and p, p'-dihydropyran, p, p'-drops, it is indicated that endrin and p, p'- DDT decomposition occurs, if the degradation rate of a single component >= 15% or the sum of the degradation rate of both >= 30%, the need for injection Mouth and column head for maintenance. After the system inspection, before the determination of the sample.

Total degradation rate% = DDT degradation rate% Endrin degradation rate% (5)