HJ 1054-2019Soil and sediment -- Determination of dithiocarbamate pesticides -- Headspace gas chromatography (English PDF)

8.1 Sample collection and storage

Collection and preservation of soil samples in accordance with the relevant regulations of HJ/T 166; in accordance with GB 17378.3, GB 17378.5, the relevant regulations of HJ 494, HJ 495 and HJ/T 91 are used to collect and preserve sediment samples.

The samples should be stored in clean sampling bottles (7.6), and protected from light, sealed and refrigerated during transportation. Such as temporarily Analysis, the samples should be stored under 4 ° C under cold storage for no more than 5 days.

8.2 Determination of moisture

When weighing a sample, another sample is weighed for moisture determination. Determination of dry matter content in soil samples according to HJ 613 the water content of the sediment sample was measured in accordance with GB 17378.5.

8.3 Preparation of test specimens

8.3.1 Acid hydrolysis sample

Remove stones and leaves from fresh samples and mix. Weigh 2 g (accurate to 0.01 g) sample and 3 g (fine Make sure that 0.1 g of sodium chloride (6.3) is added to a 22 ml headspace bottle, and 1.0 ml of EDTA-cysteine alkaline solution (6.9) is accurately added.

And 7.0 ml of stannous chloride-sulfuric acid solution (6.10), immediately sealed. 120 ° C on a 80 ° C thermostatic water bath shaker (7.4) After 90 minutes of frequency/min oscillation, the analysis was completed within 24 hours.

8.3.2 Unacidified sample

Remove stones and leaves from fresh samples and mix. Weigh 2 g (accurate to 0.01 g) sample and 3 g (fine Add 0.1 g of sodium chloride (6.3) to a 22 ml headspace bottle, add 8.0 ml of experimental water, and immediately seal it to 120 times.

The analysis was completed within 24 hours after shaking at room temperature for 10 minutes.

8.4 Preparation of blank samples

Quartz sand (6.14) was used in place of the sample, and blank samples were prepared in the same steps as in sample preparation (8.3).

9.1 Instrument reference conditions

9.1.1 Headspace Sampler Reference Conditions

Heating equilibrium temperature. 65 °C; Heating equilibration time. 15 min; Sampling needle temperature. 90 °C; Transmission line temperature. 115 °C;

Pressure time. 2 min; injection time. 0.04 min; needle removal time. 0.5 min.

9.1.2 Reference conditions for gas chromatography

Inlet temperature. 210 ° C; carrier gas (6.15) flow rate. 2.0 ml/min (constant flow mode); injection mode. split flow Sample (split ratio 5. 1); heating program. initial column temperature was maintained at 60 ° C for 2 min, and the temperature was increased to 10 ° C/min at 10 ° C/min for 2 min, the temperature was increased from 15 ° C/min to.200 ° C for 4 minutes; detector temperature. 280 ° C; flow of makeup gas (6.15). 30 ml/min.

9.2 Establishment of working curve

Add 2 g (accurate to 0.01 g) quartz sand (6.14), 3 g (accurate to 0.1 g) chlorine to 7 headspace bottles in this order.

Sodium chloride (6.3), 7.0 ml of stannous chloride-sulfuric acid solution (6.10), and 1.0 ml of standard use solution (6.13) with different concentrations, Immediately seal and prepare mancozeb containing 0.20 µg, 0.60 µg, 1.00 µg, 2.00 µg, 6.00 µg, 10.0 µg and 20.0 µg standard series. Place the prepared standard series samples on an 80 ° C thermostatic water bath shaker (7.4) at 120 times/min.

After 90 minutes of frequency oscillation, according to the instrument's reference conditions (9.1), sample injection and analysis were performed from low concentration to high concentration, and the peak surface was recorded Product or peak height. Take the content of mancozeb in the standard series solution (µg) as the abscissa, and its corresponding peak area or peak height as Vertical coordinate, establish working curve.

9.3 Standard sample chromatogram

Under the recommended instrument reference conditions (9.1) of this standard, the reference chromatogram of manganese zinc acidolysis to form carbon disulfide is shown in figure 1.

Figure 1 Standard chromatogram of manganese zinc acidolysis to form carbon disulfide

9.4 Sample determination

Place the prepared acidolysis sample (8.3.1) and the non-acidification sample (8.3.2) on the automatic headspace sampler (7.3).

The measurement of the sample is carried out according to the same instrument conditions as the working curve (9.2).

9.5 Blank test

Follow the same procedure as for sample measurement (9.4) to measure the blank sample (8.4).

10.1 Qualitative analysis

Characterized by the retention time of the reaction of mancozeb to form carbon disulfide. Before sample analysis, a retention time window t ± 3s should be established.

t is the average retention time of the target compound at each concentration level during the initial calibration, and s is the target at each concentration level during the initial calibration Standard deviation of compound retention time. When analyzing a sample, the target compound should peak within the retention time window.

10.2 Calculation of results

The total amount of dithiocarbamate (salt) pesticides in soil is calculated according to formula (1).

dmwm

= 011 (1)

In the formula. 1w-total amount of dithiocarbamate (salt) pesticides in soil (calculated as mancozeb), mg/kg;

1m-the mass of mancozeb in the acid hydrolysis sample obtained from the working curve, µg;

0m-mass of carbon disulfide converted to mancozeb in the unacidified sample obtained from the working curve, µg;

m-sample volume (wet weight), g;

dmw-dry matter content in soil sample,%.

The total amount of dithiocarbamate (salt) pesticides in the sediment is calculated according to formula (2).

OHw'm

In the formula. 2w-total dithiocarbamate (salt) pesticides in sediment (calculated as mancozeb), mg/kg 2m-mass of mancozeb in the acid hydrolysis sample obtained from the working curve, µg;

3m-Mass of carbon disulfide converted to mancozeb in the unacidified sample obtained from the working curve, µg;

'm-sample volume (wet weight), g;

OHw 2-moisture content of sediment sample,%.

The total amount of dithiocarbamate (salt) pesticides in soil or sediment is counted by carbon disulfide and calculated according to formula (3) Count.

wwcs x= 574.0

In the formula.

csw-total dithiocarbamate (salt) pesticides in soil or sediment (calculated as carbon disulfide), mg/kg;

0.574--Coefficient converted to manganese zinc into carbon disulfide;

w-total amount of dithiocarbamate (salt) pesticides in soil (1w) or sediment (2w) Manganese zinc meter), mg/kg.

10.3 Representation of results

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 three significant digits are retained.

11.1 Precision

Six laboratories added blank stones with manganese zinc content of 0.30 mg/kg, 1.00 mg/kg, and 9.00 mg/kg, respectively.

British sand spiked samples were measured in 6 replicates. Relative standard deviations in the laboratory were 1.4% to 4.1%, 1.1% to 3.8% and 0.9% to 2.6%; the relative standard deviations between laboratories were 6.8%, 9.9%, and 8.2%; the repeatability limits were 0.02 mg/kg, 0.08 mg/kg, and 0.48 mg/kg; the reproducibility limits are 0.06 mg/kg, 0.28 mg/kg, and 2.0 mg/kg, respectively.

Six laboratories added sandy soils with manganese zinc content of 0.30 mg/kg, 1.00 mg/kg, 9.00 mg/kg Soil, loam soil and clay soil samples were measured in 6 replicates. Relative standard deviations in the laboratory are 1.6% to 8.6%, 1.8% to 4.8%, and 1.1% to 5.1%; the relative standard deviations between laboratories were 9.0%, 9.6%, and 5.6%, respectively;

Repeatability limits are 0.04 mg/kg, 0.08 mg/kg, and 0.80 mg/kg, respectively; reproducibility limits are 0.08 mg/kg, 0.27 mg/kg and 1.6 mg/kg.

Six laboratories spike lake-type sediments and rivers with manganese zinc content of 1.00 mg/kg and 9.00 mg/kg, respectively.

Flow pattern sediment samples were measured in 6 replicates. Relative standard deviations in the laboratory were 1.8% ~ 4.0% and 1.3% ~ 5.8%; relative standard deviations between laboratories were 11% and 6.8%; repeatability limits were 0.07 mg/kg and 1.1 mg/kg, respectively;

Reproducibility limits were 0.32 mg/kg and 1.9 mg/kg, respectively.

Refer to Appendix A for summary data of the method precision using the mancozeb and carbon disulfide meters.

11.2 Accuracy

Six laboratories for sand-type manganese zinc supplemented with sand content of 0.30 mg/kg, 1.00 mg/kg and 9.00 mg/kg Soil, loam-type soil, clay-type soil samples and mancozeb were spiked at 1.00 mg/kg Soil samples were tested in 6 replicates. The spiked recovery ranges are. 87% ~ 113%, 82% ~ 107%, 91% ~ 106% and 87% ~ 107%, the final recoveries are. 101% ± 18%, 96% ± 18%, 101% ± 12%, and 100% ± 15%.

Six laboratories spike lake-type sediments and rivers with manganese zinc content of 1.00 mg/kg and 9.00 mg/kg, respectively.

Flow pattern sediment samples were measured in 6 replicates. Spike recovery rates range from 81% to 110% and 85% to 103%, respectively.

Final recovery rate. 99% ± 22%, 94% ± 12%.

See Appendix A for a summary of the accuracy of the mancozeb and carbon disulfide meters.

12.1 Blank test

Analyze at least one laboratory blank every 20 samples or batches (less than 20 samples/batch). Laboratory blank test the results should be below the method detection limit.

12.2 Calibration

The correlation coefficient of the working curve is >= 0.995, otherwise the working curve is re-established. Every 20 samples or batch (less (20 samples/batch) to perform a calibration of the middle concentration point of the working curve, the relative error of the measured value of the calibration point should be ± 15% Within.

12.3 Parallel samples

Every 20 samples or each batch (less than 20 samples/batch) should analyze at least one parallel sample, the results of parallel sample analysis the relative deviation should be <=30%.

12.4 Matrix Spiking

Every 20 samples or each batch (less than 20 samples/batch) should analyze at least one matrix plus standard sample, and matrix plus standard back the yield should be between 70% and 130%.