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8.
2.
2.
1 Scope of application
It is suitable for the determination of melengestrol acetate , chlorgestrol acetate and megestrol acetate residues in milk and milk powder by liquid chromatography tandem mass spectrometry
.
The detection limit of the method: the detection limit of melengestrol acetate, megestrol acetate and chlorgestrol acetate in milk are all 2μg/kg; the detection limit of melengestrol acetate, megestrol acetate and chlorgestrol acetate in milk powder are all 2μg/kg; The detection limit of ketone is 20μg/kg
8.
2.
2.
2 Principle of the method
After the fat is extracted from the milk sample, it is extracted with acetonitrile , and after saponification, it is purified by a cyanopropyl solid phase extraction column, separated by a C 18 chromatographic column, detected by liquid chromatography-tandem mass spectrometry, and quantified by an external standard method
.
8.
2.
2.
3 Reagents and materials
Acetonitrile, methanol, ethyl acetate , n-hexane: chromatographically pure; magnesium chloride (MgCl 2 : 6H 2 O), sodium hydroxide , formic acid, 25% ammonia, 95% ethanol, petroleum ether , anhydrous sodium sulfate : analytically pure
.
Ethyl acetate + n-hexane (1+19, v/v): Measure 10 mL of ethyl acetate and mix with 190 mL of n-hexane
.
Ethyl acetate + n-hexane (1+4, v/v): measure 40 mL of ethyl acetate and mix with 160 mL of n-hexane
Acetonitrile + water (7+3, v/v): Measure 700 mL of acetonitrile and mix with 300 mL of water, and shake well
.
Standard materials: melengestrol acetate, chlorgestrol acetate and megestrol acetate, with purity ≥97%
.
1000μg/mL standard stock solution: accurately weigh out 0.
0500g of melengestrol acetate, chlorgestrol acetate and megestrol acetate standard substances in a 50mL volumetric flask, dissolve it with methanol and make the volume constant
.
The standard stock solution is stored at 4°C
100μg / mL standard solution mixing the I
.
Draw 10.
1.
0ug/mL mixed standard solution II
.
Take 1.
Matrix mixed standard working solution: Take an appropriate amount of mixed standard solution II, and use the blank sample extract to prepare matrix mixed standard solutions of different concentrations
.
The standard working solution is ready to use
Cyanopropyl solid phase extraction column or equivalent: 3mL/500mg
.
Before use, rinse with 5mL ethyl acetate and 6mL n-hexane respectively to keep the column moist
8.
2.
2.
4 Instruments and equipment
Liquid chromatography-tandem mass spectrometer: equipped with electrospray ionization source (ESI)
.
Analytical balance: Sensitivity 0.
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