SN 0693-1997Determination of methoprene residues in foods of plant origin for export (English PDF)

4.15 TPT solid phase extraction column 1). 2 000 mg, 12 mL, or equivalent. a

6.1 Sample preparation

Grains, nuts and tea samples. Take a representative sample of about 500 g, crush them with a grinder and pass through a 20-mesh sieve; fruits, Vegetable and mushroom samples. Take a representative sample of about 500 g, and homogenize with a homogenizer or tissue masher. After sample preparation, Inside the clean sample bottle, seal and mark it.

6.2 Sample storage

Samples of grains, nuts and tea should be stored at 0 °C~4 °C, and samples of fruits, vegetables and mushrooms should be kept frozen below -18 °C. Pumping in the process of sampling and sample preparation, the samples should be prevented from being contaminated or from changing the content of residues.

7.1 Extraction

7.1.1 Vegetables, fruits and mushrooms. Weigh 5 g sample (accurate to 0.01 g) into a 50 mL centrifuge tube, and add 20 mL acetonitrile (4.1) and 5 g sodium chloride (4.5), shake and extract for 30 min, centrifuge the sample tube at 5,000 r/min for 5 min. Aspirate the supernatant Anhydrous sodium sulfate (4.6) is filtered and collected in a chicken heart bottle, and 20 mL of acetonitrile (4.1) is added to the residue to repeat the above extraction step.

Combine the supernatants. Place the extract in a water bath at 40 °C by rotary evaporation and concentrate it to near dryness, and then dissolve it with 2 mL of n-hexane (4.3) Residue, to be purified.

7.1.2 Grains and nuts. Weigh 5 g sample (accurate to 0.01 g) into a 50 mL centrifuge tube, add 10 mL of water and soak for 30 min, Add 20 mL acetonitrile (4.1) and 5 g sodium chloride (4.5), shake and extract for 30 min, centrifuge the sample tube at 5 000 r/min 5 min. The supernatant was filtered through anhydrous sodium sulfate (4.6) and collected in a chicken heart bottle. Add 20 mL of acetonitrile (4.1) to the residue.

Repeat the above steps and combine the supernatants. Place the extract in a water bath at 40 °C by rotary evaporation and concentrate it to near dryness, and then use 2 mL of positive Hexane (4.3) dissolves the residue and is to be purified.

7.1.3 Tea. Weigh 2 g sample (accurate to 0.01 g) into a 50 mL centrifuge tube, add 5 mL of water to soak for 30 min, add

1) TPT solid phase extraction column is the product name of Agela. This information is given for the convenience of users of this standard, and does not mean that Product recognition. If other equivalent products have the same effect, these equivalent products can be used.

20 mL acetonitrile (4.1) and 5 g sodium chloride (4.5) were shaken and extracted for 30 minutes, and the sample tube was centrifuged at 5,000 r/min for 5 minutes.

Aspirate the supernatant and filter with anhydrous sodium sulfate (4.6) and collect it in a chicken heart bottle. Add 20 mL of acetonitrile (4.1) to the residue and repeat the process.

The above steps, the supernatants were combined. Place the extract in a water bath at 40 °C by rotary evaporation and concentrate it to near dryness, and then use 2 mL of n-hexane (4.3) Dissolve the residue and wait to be purified.

7.2 Purification

7.2.1 Vegetables, fruits and grains. connect the graphitized carbon solid phase extraction column (4.14) to the neutral alumina solid phase extraction column (4.13) in series the end is activated with 5 mL acetone-n-hexane solution (4.7) and 5 mL n-hexane (4.3) at a flow rate of 1 mL/min. Will be net Transfer the chemical solution to the serial solid phase extraction column and load the sample, discard the effluent; then wash the chicken heart with 2.5 mL of acetone-n-hexane solution (4.7) Bottle, and transfer the washing liquid to the solid phase extraction column, collect the eluate, repeat the above elution operation three times, pay attention to the Always keep the column from drying out. The eluent was collected and concentrated to near dryness by rotary evaporation in a water bath at 40 °C, and the volume was dilute with n-hexane (4.3) to 1.0 mL, for GC-MS determination.

7.2.2 Tea. Add anhydrous sodium sulfate (4.6, height about 2 cm) to the TPT solid phase extraction column (4.15), first use 10 mL Acetonitrile-toluene solution (4.8) was activated at a flow rate of 1 mL/min. Transfer the solution to be purified to the solid phase extraction column for loading, and then use 2.5 mL of ethyl acetate the nitrile-toluene solution (4.8) washes the core bottle, and transfers the washing liquid to the solid phase extraction column, and starts to collect the eluate, and repeats the washing and elution operations were performed three times, and finally eluted with 5 mL of acetonitrile-toluene solution (4.8). Collect all eluates in a 40 °C water bath strip Concentrate the sample by rotary evaporation to near dryness, and dilute to 1.0 mL with n-hexane (4.3) for GC-MS determination.

7.3 Determination

7.3.1 Gas Chromatography-Mass Spectrometry Conditions

7.3.1.1 Chromatographic column. HP-5 ms, 30.0 m×0.25 mm×0.25 µm, or equivalent performance.

7.3.1.2 Oven heating program. Hold at 50 °C for 1 min, and increase the temperature to 280 °C at 10 °C/min for 5 min.

7.3.1.3 Temperature of the injection port. 250 °C.

7.3.1.4 GC-MS interface temperature. 280 °C.

7.3.1.5 Carrier gas. helium, purity >= 99.999%, constant flow mode. Flow rate. 1.0 mL/min.

7.3.1.6 Sampling mode. no split injection.

7.3.1.7 Injection volume. 2 µL.

7.3.1.8 Ion source temperature. 230 °C.

7.3.1.9 Quadrupole temperature. 150 °C.

7.3.1.10 Determination method. Select ion detection method (SIM).

7.3.1.11 Monitoring ion (m/z). 153, 191 (quantitative ion), 278.

7.3.2 Qualitative determination

Measure the standard solution and sample solution according to the conditions in 7.3.1.If the retention time of the mass chromatographic peak of the sample solution and the standard solution is not more than Over ±0.5%; in the mass spectrum after subtracting the background, all the selected monitoring ions appear, and the relative abundance of the qualifier ion (using Relative to the intensity percentage of the strongest ion abundance) is consistent with the relative abundance of the standard working solution with the same concentration (m/z 153.m/z 191.m/z 278=100.87.26), the allowable deviation of relative abundance does not exceed the range specified in Table 1, then it can be determined that there are pairs of should be tested.

7.3.3 Quantitative confirmation

Under the best working condition of the instrument in 7.3.1~7.3.2, inject the standard working solution with the chromatographic peak area of the analyte as the ordinate, the concentration of the standard working solution is the abscissa to draw a standard working curve, and use the standard working curve to quantify the chromatographic peaks of the analyte the response value of the chromatographic peak of the analyte in the sample solution should be within the linear range determined by the instrument; if it exceeds the linear range, a proper dilution should be carried out.

After release, the sample was injected for determination. Under the above chromatographic conditions, the retention time of methoprene is about 19.0 min, and the selected ion color of the standard product of methoprene for the spectrum, see Figure A.1 in Appendix A.

7.4 Blank test

Except that no sample is added, follow steps 7.1 to 7.3.

9.1 Limit of quantification

Gas chromatography-mass spectrometry detection method for rice, wheat, corn, orange, grape, tomato, potato, spinach, mushroom and flower the limit of quantification of methoprene in raw materials is 0.01 mg/kg, and the limit of quantification of methoprene in tea is 0.025 mg/kg.

9.2 Addition concentration and recovery rate

See appendix B for addition concentration and recovery data.

Method 2 Liquid Chromatography-Ultraviolet Detector Method