SN/T 1017.6-2019Method for the determination of tecloftalam residues in cereals for export (English PDF)

6.1 Sample preparation

Take a representative sample of about 500g (not washable with water), chop the edible part, mix thoroughly and put it in a food grinder Crushed, packed in clean containers, sealed and marked.

6.2 Sample preservation

During sample preparation, sample contamination or changes in residue content should be prevented. Store the samples in the dark below 4 ° C.

7.1 Extraction

Weigh a 10g sample (accurate to 0.01g) into a 500mL conical flask, add 20mL of water, and let stand for 2h. Add 100mL of methanol, Shocked for 30 minutes. Filter with 1cm diatomaceous earth. Add 50mL and 30mL of methanol to the Erlenmeyer flask respectively.

Filter with 1cm diatomaceous earth on the filter paper, and combine the filtrate in a 250mL Erlenmeyer flask.

7.2 Purification

After the above solution was transferred to a purification column (5.5), the first 10 mL of effluent was discarded, and the 5 mL of effluent after collection was collected for liquid chromatography-tandem Spectrometer determination and confirmation.

7.3 Determination

7.3.1 Liquid chromatography conditions

The liquid chromatography conditions are as follows.

a) Chromatographic column. ElipsePlusC18 column, 50mm × 2.1mm, 1.8µm, or equivalent;

b) Column temperature. 30 ° C;

c) injection volume. 10 µL;

d) flow rate. 0.3mL/min;

See Table 1 for mobile phase and gradient elution conditions.

SN/T 1017.6-2019

Table 1 Mobile phase and gradient elution conditions

time

(Min) Methanol (%)

0.1% formic acid aqueous solution (%) 0.0 40 60 0.5 40 60 2.5 95 5 5 4.5 95 5 5 4.6 40 60 6.0 40 60

7.3.2 Mass spectrometry reference conditions

The mass spectrometry conditions are as follows.

a) Ionization method. Electrospray ionization (ESI);

b) scanning method. negative ion scanning;

c) Detection method. multiple response monitoring (MRM);

d) Electrospray voltage. 2400V;

e) The sheath gas and auxiliary gas are both high-purity nitrogen, and the collision gas is high-purity argon. The gas flow should be adjusted before use to achieve mass sensitivity for testing requirements, see Appendix A for reference conditions.

f) Monitoring ion pairs (m/z). 399.9/212.8 (quantitative ions), 399.9/185.9.

7.3.3 Detection and confirmation of liquid chromatography-tandem mass spectrometry

According to the content of the test sample liquid in the sample, select the concentration of the response value of the test object within the linear response range of the instrument for measurement, such as If it exceeds the linear response range of the instrument, it should be diluted. The reference retention time of cumene in the above chromatographic conditions is about 3.9 min.

See Appendix B for liquid selective ion chromatograms. Determine the sample and standard working solution according to the conditions of liquid chromatography-tandem mass spectrometry.

The deviation between the retention time of the substance and the retention time of the test substance in the standard solution is within ± 2.5%. The standard curve method was used for quantitative determination.

The characterization should be consistent with the relative abundance of a standard working solution of comparable concentration. The allowable deviation of relative abundance does not exceed the range specified in Table 2.

It can be judged that the corresponding test object exists in the sample.

Table 2 Maximum allowable deviation of relative ion abundance during qualitative confirmation

Relative ion abundance > 50 > 20 ~ 50 > 10 ~ 20 <=10 Allowable relative deviation ± 20 ± 25 ± 30 ± 50

7.4 Blank experiment

Except that the sample is not weighed, the above steps are performed.

9.1 Limit of quantitation

The limit of quantification of this method is 0.01 mg/kg.

9.2 Determination of concentration range and recovery rate

The experimental data of the concentration and recovery of this method are shown in Table 4.

Table 3 Recovery ranges of different levels of cumene in brown rice

Matrix name addition level recovery range /% brown rice 0.01 mg/kg 88.3 to 105.1 0.20 mg/kg 89.9 to 107.3 0.40 mg/kg 81.6 to 101.4 wheat 0.01 mg/kg 94.2 to 102.5 0.20 mg/kg 89.1 to 105.1 0.40 mg/kg 92.5 to 104.2 corn 0.01 mg/kg 93.6 to 106.1 0.20 mg/kg 93.6 to 105.3 0.40 mg/kg 89.5 to 103.2 Lentils 0.01 mg/kg 91.6 to 105.6 0.20 mg/kg 84.6 to 100.5 0.40 mg/kg 92.6 to 99.1 Second method gas chromatography

13.1 Sample preparation

The sample is reduced to 1kg by the quarter method, all ground and passed through a 20-mesh sieve, mixed, divided into two parts, and packed into clean containers.

As a sample, seal and mark.

13.2 Sample preservation

Store the sample at -5 ° C or lower in the dark.

Note. During the operation of sampling and sample preparation, prevent the sample from being contaminated or changing the content of residues.

14.1 Extraction

Weigh about 10g of the sample (accurate to 0.01g) into a 250mL conical flask, add 20mL of water, and let it stand for 2h. Add 100mL of acetone, Swing for 30 min. Filter with 1cm diatomaceous earth. Add 50mL of acetone to the Erlenmeyer flask and apply 1cm of diatomaceous earth with the above.

Filter paper was used for suction filtration, and the filtrates were combined in a 250 mL pear-shaped bottle, and concentrated by rotation at 40 ° C in a water bath to about 20 mL.

The above solution was washed into a 250 mL separatory funnel with 100 mL of a 5% sodium chloride aqueous solution and 50 mL of ethyl acetate, and shaken.

After 5 min, the layers were separated and the ethyl acetate layer was transferred to another 250 mL Erlenmeyer flask. The same operation was performed with 50 mL of ethyl acetate. merge the filtrate was added with 20 g of anhydrous sodium sulfate and shaken, and then filtered into a 250 mL pear-shaped bottle. Wash the Erlenmeyer flask and filter paper with 20 mL of ethyl acetate SN/T 1017.6-2019 the remaining residues were combined in a pear-shaped bottle, and concentrated in a 40 ° C water bath to dryness.

The residue was washed into a 100-mL separatory funnel with 30 mL of n-hexane (11.4) and 30 mL of acetonitrile (11.1), shaken for 5 minutes, and left to stand.

The layers were separated and the acetonitrile layer was retained. Add 30 mL of acetonitrile (11.1) to the n-hexane layer, repeat the above operation, and combine the acetonitrile layers to separate at 125 mL in the funnel. Add 50mL of n-hexane, shake the 5min acetonitrile layer and transfer to a 250mL pear-shaped bottle, and rotate to concentrate in a 40 °C water bath