SN 0654-1997Determination of Clenbuterol Residues in Exported Fruits Gas Chromatography and Gas Chromatography-Mass Spectrometry / Mass Spectrometry (English PDF)

7.1 Extraction

Weigh 5.0 g sample (accurate to 0.01 g) and place it in a 50 mL centrifuge tube. Add 5 mL 10% phosphoric acid solution (4.9) to soak 5 min, add 25 mL acetonitrile (4.2) and 7 g sodium chloride (4.6) vigorously vortex and shake to extract for 10 min, at 5 000 r/min Centrifuge for 5 min, and take 10 mL of the supernatant in a 15 mL test tube with a stopper for purification.

7.2 Purification

Add 100 mg PSA filler, 50 mg C18 filler and 30 mg GCB filler into the above-mentioned stoppered test tube filled with supernatant.

Vortex for 1 min, centrifuge at 5,000 r/min for 1 min, and accurately pipette 5 ml of the purification solution into a 15 mL test tube with a stopper, and blow nitrogen to the temperature at 40 °C Nearly dry, add 1.0 mL of n-hexane (4.1) to dissolve the residue and sonicate for 15 s, then add 0.1 g of anhydrous sodium sulfate (4.7) to remove water, vortex for 1 min, pass through a 0.22 µm filter membrane and inject it into a gas chromatograph or gas chromatograph-mass spectrometer/mass spectrometer for analysis.

7.3 Determination

7.3.1 Instrument conditions

7.3.1.1 The reference conditions of gas chromatography are as follows.

a) Chromatographic column. HP-5, column length 30 m, inner diameter 0.32 mm, film thickness 0.25 µm or equivalent performance column;

b) Column temperature program. keep the initial temperature at 50 °C for 1 min, increase the temperature to 180 °C at 8 °C/min, keep it for 1 min, and then Increase the temperature to 300 °C at 20°C/min and keep it for 2 min;

c) Temperature of the inlet. 240°C;

d) Detector temperature. 300 °C;

e) Carrier gas. Nitrogen (purity >= 99.999%), 1.0 mL/min;

f) Makeup gas. nitrogen (purity >= 99.999%), 30 mL/min;

g) Sampling method. splitless sampling;

h) Injection volume. 1.0 µL.

7.3.1.2 The reference conditions of gas chromatography-mass spectrometry/mass spectrometry are as follows.

a) Chromatographic column. HP-5 MS, column length 30 m, inner diameter 0.25 mm, film thickness 0.25 µm or equivalent performance column;

b) Column temperature program. keep the initial temperature at 50 °C for 1 min, raise the temperature to.200 °C at 10°C/min, keep it for 1.5 min, and then Increase the temperature to 300 °C at 20°C/min and keep it for 2 min;

c) Inlet temperature. 260°C;

d) Chromatography-mass spectrometry interface temperature. 280°C;

e) Ion source temperature. 180°C;

f) Carrier gas. helium (purity >= 99.999%), 1.0 mL/min;

g) Ion source. electron bombardment source (EI source)

h) Sampling mode. splitless injection, 1.5 min open valve;

i) Injection volume. 1.0 µL;

j) Solvent delay. 5 min;

k) Scanning mode. Multi-reactive ion monitoring mode (SRM); its parent ion m/z 147.97, product ion m/z are 104.87*, 78.97, 69.93.a

7.3.2 Determination by gas chromatography

According to the content of the analyte in the sample solution, select a standard series of working solutions with similar content. To be tested in standard working solution and sample solution the corresponding values of the pesticides should all be within the linear range of the instrument. The standard working solution and the sample solution are of equal volume and inserted into the sample for determination. In the above chromatographic strip the retention time of captan is about 18.81 min. For the chromatogram of the standard product, please refer to Figure A.1 in Appendix A.

7.3.3 Determination and confirmation by gas chromatography-mass spectrometry/mass spectrometry

According to the content of the analyte in the sample solution, select a standard working solution with a similar concentration. Captan in standard working solution and sample solution the response value should be within the linear range of the instrument detection. Equal volume of standard working solution and sample solution are inserted into the sample for determination. If the sample solution and the standard in the selected ion chromatogram of the quasi-working solution, there are chromatographic peaks at the same retention time, and the quality of the sample after deducting the background in the chromatogram, the selected ions all appear, and the abundance ratio of the selected ion and the abundance ratio of the corresponding ion of the standard product are within the allowable range.

(See Table 1 for the allowable range), then it can be determined that there is a corresponding analyte in the sample. Under the conditions of 7.3.1.2, the retention time of captan is at 18.94 min, the gas chromatography-mass spectrometry/mass spectrometry MRM diagram is shown in Figure A.2.in Appendix A.

7.3.4 Blank test

Except that the sample is not weighed, all are carried out according to the above-mentioned measuring conditions and procedures.

9.1 Low limit of determination

The lower limit of the determination of this method is 0.02 mg/kg by gas chromatography, and 0.01 mg/kg by gas chromatography-mass spectrometry/mass spectrometry.

9.2 Recovery rate

The experimental data of the added concentration and recovery rate of the sample are shown in Table 2 and Table 3.

Appendix A

(Normative appendix) Gas Chromatography and Gas Chromatography-Mass/Mass Spectra of Captan

Figure A.1 Gas chromatographic standard spectrum of captan (0.02 mg/L)

Figure A.2 MRM diagram of captan standard solution gas chromatography-mass spectrometry/mass spectrometry (0.01 mg/L)