Determination of Levamisole Residues in Milk and Milk Powder by Liquid Chromatography-Tandem Mass Spectrometry

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It is suitable for the determination of levamisole residues in liquid milk (including raw milk, pure milk, skimmed milk) and milk powder (including pure milk powder, skimmed milk powder and infant formula milk powder)

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Extract the levamisole residues in milk and milk powder samples with ethyl acetate in an alkaline environment , and use dilute hydrochloric acid to convert the levamisole in the extract into levamisole hydrochloride and back up to the hydrochloric acid layer.

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Ethyl acetate, acetonitrile , methanol: chromatographically pure; sodium hydroxide , concentrated hydrochloric acid, ammonia, sodium chloride: analytically pure; formic acid: excellent grade pure; anhydrous sodium sulfate : burned at 650°C for 4 hours before use, and dried After cooling in the device, it is reserved

0.

Levamisole hydrochloride standard (levamisole hydrochloride, CAS 16595-80-5): purity ≥98%

Standard stock solution: accurately weigh an appropriate amount of standard substance, dissolve it with methanol, transfer to a 50mL brown volumetric flask, and dilute to the mark

Standard intermediate solution: Draw 1.

Standard working solution: draw an appropriate amount of standard intermediate solution as needed, dilute to the required concentration with mobile phase, and prepare before use

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Liquid chromatography-tandem mass spectrometer: equipped with electrospray ion source (ESI); solid phase extraction purification device; analytical balance: sensitivity 0.

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(1) Sample preparation

Take out a representative sample of about 1kg from all the samples, mix them well, divide them into two parts, and put them into clean containers

(2) Extraction

a.

b.
Milk powder sample Weigh 12.
5g milk powder in a beaker, add an appropriate amount of water at 35～50℃ to dissolve it, after cooling to room temperature, dilute to 100mL with water, and mix thoroughly
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Measure 10mL of the solution in a 50mL polypropylene centrifuge tube, and follow the milk sample extraction procedure
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(3) Purification

Load 10 mL of the obtained extract on the SCX cartridge, and wash with 3 mL of water, 1 mL of 0.
2 mol/L hydrochloric acid, and 3 mL of methanol, and eluted with 4.
0 mL of ammonia-methanol solution
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Blow dry the eluent with a nitrogen dryer, dilute the volume to 1 mL with mobile phase, and pass through a 0.
2um filter membrane
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For liquid chromatography-tandem mass spectrometry determination
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