Determination of 16 sulfonamide residues in milk and milk powder. Liquid chromatography-tandem mass spectrometry (1)

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1 Scope of application

Suitable for 16 kinds of sulfonamides in milk and milk powder ( sulfacetamide , sulfamethazine, sulfapyridine , sulfamethoxazine, sulfa-p-methoxypyrimidine , sulfachloropyridazine, sulfamethoxazole, sulfamethoxazole) Oxypyrimidine , sulfa-6-methoxypyrimidine, sulfamethazine, sulfaquinoxaline, sulfadiazine, sulfathiazole, sulfamethizole, trimethoprim and sulfamethoxazole) residual amount Liquid chromatography-mass spectrometry/mass spectrometry
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2 Principle of the method

The sulfonamide residues in the sample were extracted with perchloric acid solution, purified by Oasis HLB solid phase extraction column, eluted with methanol , determined by liquid chromatography-mass spectrometry/mass spectrometry, and quantified by external standard method
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3 Reagents and materials

Perchloric acid: pure superior grade
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Perchloric acid solution: pH=2, add 1mL perchloric acid to 1000mL water, then adjust to pH=2 with water
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Sulfacetamide, Sulfamethazine, Sulfapyridine, Sulfamethoxazine, Sulfamethoxine, Sulfachloropyridazine, Sulfamethoxazole, Sulfamethoxazole, Sulfa-6-methoxypyrimidine , Sulfamethazine, sulfaquinoxaline, sulfadiazine, sulfathiazole, sulfamethizole, trimethoprim and sulfamethoxazole standard substances: purity ≥95%
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1mg/mL 16 kinds of sulfa standard stock solutions: accurately weigh an appropriate amount of each sulfa standard substance, and use methanol to prepare a 0.
1 mg/mL standard stock solution, and store the solution at 4°C
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1ug/mL sulfonamide mixed standard intermediate solution: pipet 1mL standard stock solution into a 100mL volumetric flask, and dilute to the mark with methanol
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Matrix mixed standard working solution: According to the sensitivity of each sulfonamide and the linear range of the instrument, the blank sample extract is used to prepare matrix mixed standard working solutions of different concentrations (ng/mL).
The matrix mixed standard working solutions are stored at 4°C
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4 Apparatus and equipment

Liquid chromatography-tandem quadrupole mass spectrometer, equipped with electrospray ion source
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5 Sample pretreatment

(1) Sample preparation

Take the milk out of the refrigerator, place it at room temperature, shake well, and set aside
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(2) Extraction

Milk: Weigh 2g sample, accurate to 0.
01g, put it in a 50mL plastic centrifuge tube with stopper, add 25mL perchloric acid solution, vortex shaker to extract 1min, ultrasonic extraction for 10min
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Milk powder: Weigh 0.
5g sample, accurate to 0.
01g, put it in a 50mL plastic centrifuge tube with a stopper, add 25mL perchloric acid solution, vortex and extract for 1min, ultrasonic extraction for 10min
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(3) Purification

Transfer all the solution obtained in the extraction step to the reservoir, then wash the centrifuge tube with 5 mL of perchloric acid solution, combine the washing liquid into the reservoir, and pass through the HLB solid phase extraction column at a flow rate of about 1 mL/min.
After the liquid has completely flowed out, rinse the column with 5 mL of water, drain it, and elute with 3 mL of methanol in a 10 mL graduated centrifuge tube.
The eluent is blown to about 0.
2 mL with nitrogen at 40°C to stop concentration, and use methanol-acetic acid solution Make up to 1mL
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Take 2g of milk negative sample and 0.

Related Links: Determination of 16 Sulfa Residues in Honey Liquid Chromatography-Tandem Mass Spectrometry (3)