Determination of chloramphenicol, thiamphenicol and florfenicol residues in edible animal muscle, liver and aquatic products-scope of application and principle of the method

4.
2.
2.
1 Scope of application

It is suitable for the determination of chloramphenicol, thiamphenicol and florfenicol residues in edible animal muscle, liver, fish and shrimp by liquid chromatography-tandem mass spectrometry
.

4.
2.
2.
2 Principle of the method

The residues of chloramphenicol, thiamphenicol and thiamphenicol in the sample are extracted with alkaline ethyl acetate , and the extract is rotated and evaporated to dryness.
The residue is dissolved in water and defatted by n-hexane liquid-liquid distribution for high-efficiency liquid Analyzed by gas chromatography-tandem mass spectrometer, the peak area was quantified by internal standard method
.

4.
2.
2.
3 Reagents and materials

Methanol, ethyl acetate and n-hexane are chromatographic grades; ammonia (25%); anhydrous sodium sulfate: burned at 650°C for 4 hours and stored in a sealed container for later use after cooling; standard chloramphenicol, thiamphenicol and Florfenicol, purity ≥99.
5%; Chloramphenicol-D5, purity ≥98%
.

Standard stock solution: accurately weigh the appropriate amount of chloramphenicol, thiamphenicol and florfenicol standard substances, and use methanol to make a 100μg/mL standard stock solution.
The solution is stored at -18°C for one year; Mixed standard stock solution: accurately draw a certain amount of standard stock solution in a 50.
0mL volumetric flask, dilute to the mark with water, 1mL of this solution contains 20ng of chloramphenicol, thiamphenicol and thiamphenicol, this solution is in 4 The shelf life is three months at ℃
.

Internal standard stock solution 1: accurately pipet 100μL of chloramphenicol-D5 standard solution in a 10.
0mL volumetric flask, dilute to the mark with methanol, and store the solution at 4°C
.

Mixed standard working solution: According to the sensitivity of each standard and the linear range of the instrument, draw a certain amount of mixed standard stock solution and internal standard stock solution before use, and mix with water to make a mixed standard working solution of appropriate concentration
.

4.
2.
2.
4 Instruments and equipment

Liquid chromatography-tandem mass spectrometer: equipped with electrospray ion source; analytical balance: sensitivity 0.
1mg and 0.
01g; centrifuge: 4000r/min; high-speed desktop centrifuge: 13000r/min; tissue masher; homogenizer ; Rotary evaporator; ultrasonic; liquid mixer; polypropylene centrifuge tube: 50mL, 1.
5mL, with stopper; chicken heart flask: 25mL; colorimetric tube: 50mL, with stopper
.

4.
2.
2.
5 Sample pretreatment

(1) Sample preparation

Take about 500g of the sample and grind it with a meat tissue masher, put it into a clean container as a sample, seal it, and mark it
.

(2) Extraction

Weigh 5g sample, accurate to 0.
01g
.

(3) Purification

Dissolve the residue in the chicken heart bottle with 3 mL of water, sonicate for 5 minutes, add 3 mL of n-hexane and vortex for 30 s, let stand for layering, discard the upper layer of n-hexane, add 3 mL of n-hexane, vortex and mix for 30 s, stand for layering, Pipette 1mL of the water phase into a 1.