Analysis of Residues in Apples and Soils by Gas Chromatography

Residue Analysis of Endosulfan in Apple and Soil Gas Chromatograph Technical Specifications:

Temperature Control Detector FID

Temperature control range: 7°C～400°C (increment 0.1°C) at room temperature Detection limit: ≤5×10-12g/s (n-hexadecane)

Cheng Shengjie: Third-order baseline noise: ≤6×10-12A/H

Cheng Sheng rate: 0.1 °C ~ 50 °C/min (increment 0.1 °C) linear range: ≥ 105

Stabilization time: <20min

Detector TCD

Sensitivity: ≥10000mV·ml/mg(n-hexadecane)

Baseline noise: ≤30uV (hydrogen with 99.999 carrier gas)

1. Gas Chromatograph Analysis of Principles of Endosulfan Residues in Apple and Soil

Samples were extracted with acetone or petroleum ether, the extracts were filtered, column chromatography with Florisil or alumina, and gas chromatography (ECD) measurements.

2. Sample processing

(1). extract

Apple sample: Weigh 50g of chopped sample, add 70mL of acetone, mash, suction filtration, add 200mL of 10% NaCl solution, shaking, extraction with petroleum ether, the extract was concentrated to near dry.

Soil samples: Weigh 25 g of soil in stoppered flasks, add 60 mL of petroleum ether/acetone (l:l, V/V) mixture, extract with ultrasound for 10 min, filter in a separatory funnel, and add the above mixture 60 mL. The same extraction 10min, filtered in a separatory funnel, the residue was washed twice with 20mL, 20mL extract, then in a separatory funnel was added 5mL8% NaCl solution, shaking, layering, the organic layer was filtered through anhydrous sodium sulfate in a circle In the bottom flask, it was extracted three times with 20 mL×3 petroleum ether, filtered, and the petroleum ether layer was combined and concentrated to about 5 mL at 65° C., to be purified.

Cottonseed samples: Weigh 10g cottonseed mash, add 250mL bottle with plug, add 100mL acetone / petroleum ether (1: l, V / V) mixture, ultrasonic extraction 10min, filtered in a 250mL separatory funnel, and then Add 70mL of the above mixture for extraction for 10min, filter in a separatory funnel, and wash the residue with 20mL and 20mL extracts twice. Combine in a separatory funnel, add 50mL of 8% NaCl solution, shake for 1min, layer, and pass the organic layer through the water. Sodium sulfate was filtered in a round-bottomed flask and extracted three times with 30 mL×3 petroleum ether. The petroleum ether layer was combined and concentrated to about 5 mL at 65° C., to be purified.

Cotton leaf sample: Weigh 10g chopped cotton leaves and add 100mL of petroleum ether/acetone (1:1, V/V) mixture to mash, extract, filter in a separatory funnel, and wash the residue with 20mL×3 mixture three times. In the separatory funnel, other operations are the same as cottonseeds.

(2). Column chromatography

Apple: The column was filled with 1 cm of anhydrous sodium sulfate, 1 g of florisil, 0.2 g (0.2 g of activated charcoal and 10 g of florisil), and 1 cm of anhydrous sodium sulfate from bottom to top. When it is nearly dry, add a small amount of acetone: petroleum ether (1:9, V/V) eluent, then add 30mL acetone/petroleum ether (3:7, V/V) to rinse, concentrating the eluent, and after constant volume Tested.

Cottonseeds: 25cm (length) × 2.5crn (internal diameter) glass column, 2cm thick anhydrous sodium sulfate, 3g florisil, 10g neutral alumina, 2cm thick anhydrous sodium sulfate from top to bottom. Pre-spray with 50 mL of petroleum ether, discard the eluate and transfer it to a sample. Rinse with ethyl acetate/petroleum ether (1:9, V/V). Collect 75 mL of the leachate. Concentrate to dryness. Tested.

Cotton leaf: purification method with cottonseed

Soil: 25cm (length) × 2.5cm (inside diameter) glass column, 2cm thick anhydrous sodium sulfate, 10g neutral alumina, 2cm thick anhydrous sodium sulfate from top to bottom. Pre-spray with 50ml of petroleum ether, discard the leachate, transfer to human sample, rinse with ethyl acetate/petroleum ether (1:9, V/V), receive the first 75ml of leachate, and concentrate to dryness. Capacity to be tested later.

3. Determination of Endosulfan Residues in Apple and Soil by Gas Chromatography

Condition 1: Gas chromatograph, electron capture detector (ECD); column 2m (length) × 3mm (internal diameter) glass column, filled with 2% OV-17 + 2% QF-1 / GasChromQ (80 ~ 100 mesh); detection Temperature: Column 200°C, Detection chamber 260°C, Inlet 240°C; Carrier gas: Nitrogen (>99.99%), 2.2 kg/cm3; Retention time: α-Endosulfan 8.45 min, β-Endosulfan 15.54 Min, endosulfan sulfate is 24.74 min

The minimum detection amount of this method: α-endosulfan is 2×10-11g, β-endosulfan is 4×10-11g, and endosulfan sulfate is 6×10-11g; the lowest detection concentration: α-endosulfan 0.01 Mg/Kg, β-endosulfan 0.02mg/Kg, endosulfan sulfate 0.03mg/Kg; recovery rate: apple added in a concentration of 0.05 to 0.50mg/Kg, recovery rate of α-endosulfan 82.8 to 90.8%, respectively Beta-endosulfan was 88.7 to 96.4% and endosulfan sulfate was 95.2 to 97.4%.

Condition 2: Gas chromatograph, electron capture detector (ECD); Column 1m (length) × 3mm (inner diameter), filled with 5% OV-17/Chromosorb WHP (100-120 mesh); Detection temperature: Column temperature 240°C , Detector 280 °C, sample 280 °C. Carrier gas: nitrogen (>99.99%), 60 ml/min; retention time: α-endosulfan 3.9 min, β-endosulfan 5.4 min, endosulfan sulfate 6.4 min.

The minimum detection amount of this method: α-endosulfan, β-endosulfan is 1×10-12g, and endosulfan sulfate is 1×10-11g; the lowest detection concentration: α-endosulfan and β-endosulfan are 1. ×10-3mg/Kg, endosulfan sulfate is 5×10-3mg/kg; Recovery rate: α-endosulfan, β-endosulfan, and endosulfan sulfate are all added 0.01-1.0mg/kg, soil recovery The rate was 86.3% to 99.8%, the cotton leaf was 88.2% to 99.4%, and the cottonseed was 85.6% to 99.2%.