Liquid chromatography-tandem mass spectrometry for the determination of five thiouracil drug residues in bovine thyroid and beef

19.

It is suitable for the determination of thiouracil, methylthiouracil , n-propylthiouracil, tabazole and mercaptobenzimidazole residues in beef thyroid and beef by liquid chromatography-tandem mass spectrometry .

19.

The target residue was extracted with ethyl acetate, purified with Sep-Park Amino Propyl solid phase extraction column, derivatized with 4-chloro-7-benzofurazan, and purified with Oasis HLB solid phase extraction column, liquid chromatography-tandem mass spectrometry Detection

19.

Methanol , acetonitrile and ethyl acetate are all: chromatographically pure; disodium hydrogen phosphate (Na ₂ HPO ₄ : 12H ₂ O), potassium dihydrogen phosphate (KH ₂ PO ₄ ), acetic acid, concentrated hydrochloric acid, sodium hydroxide, trichloro Methane, n-hexane, and disodium ethylenediaminetetraacetate (C ₁₀ H ₁₄ N ₂ O ₈ Na ₂ ·2H ₂ O) are all top grade pure; mercaptoethanol is analytical pure

4-Chloro-7-nitrobenzo-2-furazan (4-Chloro-7-nitrobenzo-2-furazan, NBF-CI), C ₆ H ₂ CIN ₃ O ₃ : content ≥ 9%

Phosphate buffer solution: pH=8, 0.

Sodium hydroxide solution: 1mol/L

Derivative: 5mg/mL

Disodium ethylenediaminetetraacetic acid solution: 0.

Eluent: a mixed solution of methanol and chloroform (15+85, v/v) containing 3% acetic acid

Constant volume solution: acetonitrile aqueous solution containing 0.

Standard materials: thiouracil, methyl thiouracil, n-propyl thiouracil, tapazole, mercaptobenzimidazole, purity ≥99%

Internal standard standard substance: 2-methoxethox-mercaptobenzimidazole (MEMBI), purity ≥99%

Standard stock solution: 1.

Mixed standard working solution: 0.
1μg/mL
.
Draw an appropriate amount of each standard stock solution, dilute it with methanol to a mixed standard working solution of 0.
1μg/mL, store it in the dark at -18°C, and can be used for 3 months
.

Internal standard standard stock solution: 1.
0mg/mL Weigh an appropriate amount of methyl mercaptobenzimidazole standard material, and use methanol to make a 1.
0mg/mL standard stock solution.
Store it in the dark at -18°C.
It can be used for 6 months
.

Internal standard working solution: 0.
1μg/mL
.
Draw the internal standard stock solution, dilute it with methanol to a 0.
1μg/mL internal standard working solution, store it in the dark at -18°C, and can be used for 3 months
.

Sep-Park Amino Propyl solid phase extraction column or equivalent: 500mg, 3mL
.
Pre-treatment with 20mL n-hexane before use, keep the column moist
.
Oasis HLB solid phase extraction column or equivalent: 60mg, 3mL
.
Before use, pretreated with 5mL methanol and 10mL water respectively to keep the column moist
.

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4 Instruments and equipment

Liquid chromatography-tandem quadrupole mass spectrometer, equipped with electrospray ion source; analytical balance: sensitivity 0.
1mg and 0.
01g; liquid mixer; solid phase extraction device; nitrogen drying instrument; constant temperature oscillating water bath; vacuum pump: The vacuum degree should reach 80kPa; micro syringe: 25μL, 100μL; brown centrifuge tube with stopper: 25mL, 50mL; pH meter: measurement accuracy ±0.
02pH unit; reservoir: 50mL; centrifuge: rotation speed greater than 4000r/min
.