Method for determination of carbamate pesticide residues in vegetables and fruits

Method for determination of carbamate pesticide residues in vegetables and fruits

1 Reagents and materials

Unless otherwise stated, only analytically pure reagents and primary water specified in GB/T 6682 were used in the analysis.

1.1 Acetonitrile.

1.2 Acetone, re-steamed.

1.3 Methanol, chromatographically pure.

1.4 Sodium chloride, baked at 140 ° C for 4 h.

1.5 post-column derivatization reagent, reagent package (P/N: YS-CB-001)

1.5.1 0.05mol/L NaOH solution: R315, dissolved in 1 L water.

1.5.2 OPA diluted solution: R312, dissolved in 1 L of water.

1.5.3 O-Phthaladehyde (OPA): R301.

1.5.4 Thiofluor: R302.

1.6 Solid phase extraction column, FJ-NH2-500.6: Amino column, volume 6 mL, filling 500 mg.

1.7 Filter, 0.2 μm, 0.45 μm, solvent film.

1.8 pesticide standards are shown in Table 1.

Table 1 10 carbamate pesticides and their metabolites

1.9 Pesticide standard solution preparation

1.9.1 Single pesticide standard solution, direct use of pesticide standards. (concentration is 1000mg/L)

Store in a refrigerator below -18 °C. When using, according to the response value of each pesticide on the corresponding detector, draw an appropriate amount of standard stock solution and dilute with methanol to prepare the required standard working solution.

1.9.2 Pesticide mixed standard solution

According to the response value of each pesticide on the instrument, accurately draw a certain volume of individual pesticide stock solution one by one, inject into the same volumetric flask, dilute with methanol to the scale to prepare a pesticide mixed standard stock solution, and dilute to the required quality with methanol before use. The standard working fluid concentration.

2 Instruments and equipment

2.1 Liquid chromatograph, gradient system with fluorescence detector (FLD).

2.2 Food processor.

2.3 Homogenizer.

2.4 Nitrogen blowing instrument.

2.5 Post-column Derivatization System: CoM6000PCR Double-column Post-Derivative System

3 Determination steps

3.1 Sample preparation

Same as Method 1 of the first part of NY/T 761-2008 "Determination of organophosphorus, organochlorine, pyrethroid and carbamate pesticide residues in vegetables and fruits".

3.2 Extraction

Same as Method 1 of the first part of NY/T 761-2008 "Determination of organophosphorus, organochlorine, pyrethroid and carbamate pesticide residues in vegetables and fruits".

3.3 Purification

Accurately absorb 10.00 mL of acetonitrile phase solution from a 100 mL stopper cylinder, place it in a 150 mL beaker, place the beaker on a 80 °C water-soluble pot, and slowly introduce a nitrogen or air stream into the cup to evaporate the acetonitrile. Add 2.0 mL of methanol + dichloromethane (1 + 99) to dissolve the residue, cover with aluminum foil, and purify.

The amino column was pre-washed with 4.0 mL of methanol + dichloromethane (1+99). When the solvent level reached the surface of the column adsorption layer, the above-mentioned solution to be purified was immediately added, and the eluate was collected with a 15 mL centrifuge tube. 2 mL of methanol + dichloromethane (1+99) was washed in a beaker and passed through the column and repeated once. The centrifuge tube was placed on a nitrogen gas blower, the temperature of the water bath was 50 ° C, and the nitrogen was evaporated to near dryness, and the volume was determined to be 2.5 mL with methanol. After mixing on the mixer, filter with a 0.2 μm filter and test.

3.4 Chromatographic reference conditions

3.4.1 Column

Precolumn: C18 precolumn, 600220;

Analytical column: C42545, Comatex, C18-CB, 5 μ, 250 x 4.6.

3.4.2 Column temperature, 42 ° C.

3.4.3 Fluorescence detector, λex330 nm, λem465 nm.

3.4.4 Solvent gradient and flow rate

Solvent gradient and flow rate are shown in Table 2.

Table 2 Solvent gradient and flow rate

3.4.5 post-column derivatization

3.4.5.1 Derivatizing agent 1: (See the reagent package instructions), flow rate: 0.5mL / min.

3.4.5.2 Derivatizing agent 2: (see instructions for use of the kit), flow rate: 0.5 mL/min.

3.4.5.3 Reactor temperature

Hydrolysis temperature: 100 ° C; derivatization temperature: 40 ° C.

3.5 Chromatographic analysis

20.0 μL of the standard mixed solution and the purified sample solution were separately injected into the chromatograph, and the retention time was qualitatively determined, and the peak area of ​​the sample solution was compared with the peak area of ​​the standard solution.

The company has long-term supply of COM6000 post-derivative system for the determination of carbamate pesticides, YS-CB-001 derivatization reagent package, special column for carbamate, guard column, solid phase extraction cartridge and other products. Users are welcome to call, 022-58693245/6/7.