Experimental reagent
Acetone and n-hexane (JTBaker) are all pesticide residues;
Methanol (Fisher Chemical) is chromatographically pure;
The copper sheet is of analytical grade (if it is used, the oxide layer is first removed with 6 mol/L hydrochloric acid, washed with deionized water until neutral, and then washed three times with methanol, acetone and n-hexane);
Anhydrous sodium sulfate is analytically pure (400 ° C for 4 h, stored in a closed container after cooling);
The silica gel was analytically pure (first washed with methanol, then with dichloromethane, dried overnight at 110 ° C; baked at 250 ° C for 24 h before use, stored in a closed container after cooling).
Florisil column (SUPELCO company), 1000mg (6mL);
20 kinds of organic chlorine mixed standard solution (AccuStandard): containing α-hexachlorocyclohexane, β-hexachlorocyclohexane, γ-hexachlorocyclohexane, δ-hexachlorocyclohexane, endosulfan II, endosulfan I, cis chlordane, Trans chlordane, heptachlor, epoxy heptachlor, dieldrin, aldrin, endrin, endosulfan sulfate, endrin aldehyde, endrin ketone, methoxychlor, p,p , -DDT, p, p, -DDD, p, p, -DDE a total of 20 organochlorine compounds.
Hexachlorobenzene in methanol, 100 μg/mL.
o,p,-DDT in methanol, 100 μg/mL.
In the hexane, mirex, 100 μg / mL.
Recovery indicator standards (both 10 μg/mL): α-HCH-D6, γ-HCH-D6, α-Endosulfan-D4, p, p'-DDT-D8.
Internal standard: Hexachlorobenzene-13C6 in n-hexane, 100 μg/mL.
Laboratory equipment
With autosampler gas chromatography / mass spectrometer (Agilent 6890/5973N GC / MS), cable extractor, rotary evaporator and vacuum pump, nitrogen blower, oscillator.
The glassware used was washed successively with n-hexane (3 times), acetone (3 times), and methanol (3 times), then washed with ultrasonic cleaner water, and then rinsed with tap water (3 times) and distilled water (3 times). Air dried.
Experimental Materials
2 soil samples, each of which was 3 in parallel during pretreatment. Three injections were repeated for each parallel sample during the injection analysis.
Experimental procedure
1. Extract the appropriate amount of activated silica gel, 150 mL of n-hexane / acetone (V / V = ​​1:1) in a cable extractor, continuous extraction for 7-8h. The temperature of the extraction water bath was maintained at 60 ° C, and the temperature of the cooling circulating water was adjusted to 10 ° C. After the pre-rinse was completed, the extract was discarded.
Weigh 10g of soil sample, 3 parts in parallel; 10g of activated anhydrous Na2SO4, placed in a beaker, mix well, transfer to a sock suction filter cartridge, accurately add 100μL of 10μg/mL deuteration recovery indicator. Anhydrous Na 2 SO 4 of about 2 cm in height was added, and continuous extraction was carried out for 24 h with 150 mL of n-hexane/acetone (V/V = 1:1). The extraction temperature was maintained at 60 ° C, and the temperature of the cooling circulating water was adjusted to 10 ° C. This soil analysis sample requires 3 parallel samples and a blank sample.
After the extraction is completed, the extract is cooled to room temperature, an appropriate amount of activated copper sheet is added to the extract, and the mixture is allowed to stand for about 40 minutes for desulfurization, and then the extract is concentrated to 1-2 mL with a rotary evaporator, and then 20 mL of the flask is added to the flask. The alkane was concentrated to 1-2 mL with a rotary evaporator and this was repeated twice in succession to complete solvent replacement. The concentrated extract is to be purified.
2. Purification
The soil sample was purified using a Florisil cartridge (SUPELCO), 1000 mg (6 mL).
Activation: the column was first washed with 10 mL of acetone and then with 20 mL of n-hexane;
Elution: Transfer the concentrate to be purified to an activated Florisil SPE cartridge, add 12 mL of acetone/n-hexane (V:V=2:98) mixed solvent, and receive the entire eluate with a KD tube;
3. Concentrated injection
The eluate was concentrated to about 0.8 mL with a nitrogen gas blower, then mixed with an appropriate amount of hexachlorobenzene-13C6 internal standard solution, and the volume was adjusted to 1 mL in n-hexane, and transferred to a sample bottle for GC/MS analysis. The sample volume is 1 μL.
4. GC/MS analytical instrument condition chromatography column (HP-5MS): 30m × 0.25mm × 0.25μm;
The carrier gas is high purity helium gas, and the flow rate is 1.0 mL/min;
Inlet temperature: 220 ° C;
Injection method: no split;
Temperature programmed: 90 ° C (1 min) - 40 ° C / min - 170 ° C (0 min) - 2 ° C / min - 235 ° C (3 min).
GC-MS interface temperature: 280 ° C; ion source temperature: 230 ° C; quadrupole temperature: 150 ° C;
Ion source: EI;
Qualitative analysis: SCAN, scanning range (m / z) is 35-500;
Quantitative analysis: SIM.
Precautions
1. Check whether the GC inlet cause degradation of DDT, only decomposition DDT DDD and DDE instrument degree is less than 20% of the sample can be measured.
2. Soil samples do not represent a detection result of organochlorine pesticides concentration ranges given in the table is not free of the compounds.
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