GB 29705-2013Determination of Cypermethrin, Fenvalerate and Deltamethrin residues in aquatic products by Gas Chromatographic method (English PDF)

6.1 Preparation of the sample

Take appropriate blank or fresh or thawed fish and shrimp test edible tissue, minced, and homogenized.

--- the test sample taken after homogenization, as the feed try.

--- blank sample taken after homogenization, as a blank sample.

--- blank sample taken after homogenization, adding a suitable concentration of the standard working solution, is added as a blank sample.

Save 6.2 sample

Or less at -20 °C.

Determination Step 7

7.1 Extract

Sample Weigh 5g ± 0.05g, in 50mL glass centrifuge tube with stopper, acetonitrile was added 15mL, shaking 5min, sodium chloride 1.5g vibrator Swing 2min, 4000r/min centrifugal 5min, supernatant to another glass stoppered centrifuge tube, the residue was added acetonitrile 15mL, extraction was repeated Once, twice supernatants were combined, acetonitrile, n-hexane solution was added 10mL, shaking mixing 2min, 4000r/min centrifugal 5min, the upper layer was removed Hexane solution, acetonitrile, n-hexane solution was added 10mL, extraction was repeated once, the upper n-hexane was discarded. The acetonitrile layer was taken to heart-shaped flask, to 45 °C water bath rotary evaporated to dryness, the residue was dissolved in methanol 2mL, 4 mL water was added, mixed and set aside.

7.2 Purification and concentration

5mL C18 column successively with methanol, 5mL of chloroform, methanol and aqueous methanol 5mL 5mL activation, taking stock solution through the column, the control Flow rate of 1 drop/s. 5mL rinsed with aqueous methanol, dried stream, Benzene was added 4mL, collecting eluate standby.

5mL activated alumina column with acetonitrile, the eluent through the column to take backup. Benzene was added 1mL elution, is repeated three times. Three eluent to merge 10mL graduated centrifuge tube, with the volume of benzene to 5mL, gas phase chromatography.

7.3 Preparation of standard curve

The precise amount of 5µg/mL cypermethrin, fenvalerate and deltamethrin amount standard stock solution, diluted with benzene, prepared to a concentration points Do is a series hybrid standard 0.5,1,5,25,50,100 and 500ng/mL solution, gas phase chromatography. To the measured peak area for the vertical take Standard, the standard concentration corresponding to abscissa, the standard curve. Seeking regression equation and correlation coefficient.

7.4 Determination

7.4.1 Chromatographic conditions

7.4.1.1 Detector. 63Ni electron capture detector.

7.4.1.2 Column. 5% phenyl and 95% polydimethylsiloxane.

7.4.1.3 Detector temperature. 310 °C.

7.4.1.4 Inlet temperature. 230 °C.

7.4.1.5 Injection mode. splitless.

7.4.1.6 Carrier gas. 99.999% pure nitrogen.

7.4.1.7 column flow rate. 2.5mL/min, the tail is blown. 25mL/min.

7.4.1.8 Column temperature program. initial column temperature 160 °C, maintained 1min, 30 °C/min was raised to 250 °C, maintained 2min, 5 °C/min was raised 280 °C, maintained 10min.

7.4.1.9 Injection volume. 1µL.

7.4.2 Assay

Take a sample solution and standard solutions corresponding, for single or multi-point calibration, by external standard method, the peak area is calculated. Standard solution and sample solution Liquid cypermethrin, fenvalerate, deltamethrin response value should be within the linear range of the detection instrument. In the chromatographic conditions, standard solutions FIG blank and high performance liquid chromatography was added the sample solution in Appendix A.

7.5 Blank test

But without addition of the sample, the measurement step is performed in exactly the same operation in parallel.

8 and the result of the calculation expression Residues in the specimens cypermethrin, fenvalerate, deltamethrin (µg/kg) according to formula (1).

A × cS × V

AS × m

Where.

--- for the respective X-try feed cypermethrin, fenvalerate, deltamethrin residues, in micrograms per kilogram (µg/kg);

A --- respective sample cypermethrin, fenvalerate, deltamethrin peak area;

CS --- respective standard solution cypermethrin, fenvalerate, deltamethrin concentration, in micrograms per milliliter (µg/mL);

V --- final sample volume in milliliters (mL);

--- the AS standard working solution corresponding peak area cypermethrin, fenvalerate, deltamethrin;

m --- try supply feed mass in grams (g).

Note. The blank value should be subtracted from the results, expressed as the arithmetic mean of the measurement result measured parallel to three significant figures.

9.1 Sensitivity

The detection limit of the method was 0.2µg/kg, the limit of quantitation was 1µg/kg.

9.2 Accuracy

This method recoveries on levels 70% to 100% at 1µg/kg ~ 10µg/kg.

9.3 Precision

The relative standard deviation of the method <=15%, inter-assay relative standard deviation <=20%.

Appendix A

Chromatogram

Description.

1 --- cypermethrin;

2 --- fenvalerate;

3 --- deltamethrin.

Figure A.1 cypermethrin, fenvalerate and deltamethrin chromatogram of the standard solution

(Cypermethrin 50µg/mL, fenvalerate 50µg/mL, deltamethrin 50µg/mL)

Figure A.2 grass carp muscle tissue sample blank chromatogram

Description.

1 --- cypermethrin;

2 --- fenvalerate;

3 --- deltamethrin.

Figure A.3 grass carp muscle tissue blank add cypermethrin, fenvalerate and deltamethrin sample chromatograms

(Cypermethrin 25µg/kg, fenvalerate 25µg/kg, deltamethrin 5025µg/kg)