GB 29707-2013Determination of marker residues of Amitraz in milk by Gas Chromatographic method (English PDF)

6.1 Preparation of the sample

An appropriate amount of fresh or frozen or blank test milk and mix well.

--- 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 Preparation of standard curve

The precise amount of 2,4-dimethylaniline appropriate amount of standard stock solution, diluted with hexane, and formulated to a concentration of 10,20,50,100,200 400ng/mL of the standard solution series, from each 2.0 mL, the processing according to the derivatization step, 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.

7.2 Extraction and hydrolysis

Sample Weigh 5g ± 0.05g, polypropylene centrifuge tube, the aqueous alkaline solution was added 10mL, Vortex, 4200r/min centrifugal 10min, the supernatant was further polypropylene centrifuge tube, the aqueous alkaline solution added to the residue 10mL, extraction was repeated once, the two supernatants were combined liquid. Oven temperature was allowed to stand at 70 deg.] C in 50min, cooled, hexane was added 10mL, Vortex, standing 5min, 4200r/min centrifugal 10min, the upper n-hexane solution in a round bottom flask, was added 5 mL of n-hexane extraction was repeated once underlayer, the two hexane layer were combined, in 45 °C transferred evaporated to dryness, the residue was dissolved with n-hexane 2.0mL standby.

7.3 Derivatives and purify

Stock solution taken in a stoppered centrifuge tube, add 10 L heptafluorobutyric anhydride, mixed, at 60 deg.] C thermostat 90min, 30min intervals therebetween removed Ultrasound 5min. After standing derived 10min, saturated sodium bicarbonate solution was added 2mL, mixing, the organic layer was taken, dried over anhydrous sodium sulfate was added to 2g Water, gas phase chromatography.

7.4 Determination

7.4.1 Chromatographic conditions

7.4.1.1 Column. Rtx-1 capillary column (30m × 0.25mm), or equivalent person.

7.4.1.2 Column temperature. programming, see Table 1.

Table 1 Temperature Programmed Table

Heating rate

°C/min

The initial temperature Residence time min 7.4.1.3 column flow rate. 1mL/min, analysis time. 27min.

7.4.1.4 Inlet temperature. 250 °C.

7.4.1.5 Injection volume. 1µL.

7.4.1.6 Carrier gas. nitrogen gas (purity >=99.999%), 30mL/min.

7.4.1.7 split mode. split split ratio 50 to 1.

7.4.1.8 Detector temperature. 300 °C.

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 Amitraz solution of 2,4-dimethylaniline and the response value should be within the linear range of the detection instrument. In the chromatographic conditions, the standard solutions and Blank HPLC sample solution was added in Appendix A. FIG.

7.5 Blank test

But without addition of the sample, the same steps employed in parallel operation.

Calculation and Expression of Results 8 Residues in the specimens amitraz (µg/kg) according to formula (1).

A × cS × V × 1.21

AS × m

Where.

--- for the X-feed try amitraz residues micrograms per kilogram (µg/kg);

A --- peak area of sample solution heptafluoro 2,4-dimethylphenoxy butanamide;

Standard working solution concentration cS --- 2,4-dimethylaniline, expressed in nanograms per milliliter (ng/mL);

V --- volume was extracted with hexane, milliliters (mL);

2,4-dimethyl aniline 1.21 --- double correction coefficient calculation formamidine;

--- the AS peak area of the standard working solution of 2,4-dimethylbenzene heptafluoro butanamide;

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 2µg/kg, the limit of quantitation of 5µg/kg.

9.2 Accuracy

This method of adding 5µg/kg ~ 20µg/kg on recovery levels of 70% to 110%.

9.3 Precision

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

Appendix A

Chromatogram

FIG A.1 2,4- ditolylamine chromatogram of the standard solution (10µg/L)

Figure A.2 milk blank sample chromatogram

Figure A.3 milk sample blank add amitraz chromatogram (5µg/kg)