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5.
2.
5.
1 Scope of application
Honey suitable for cefazolin , cephapirin , cephalexin , cephalosporin CTP , cefquinome residues in liquid chromatography - tandem mass spectrometry
.
Detection limit of the method: cefazolin is 10μg/kg; cefpirin, cephalexin, ceflonine, cefquinoxime is 2.
5.
2.
5.
2 Principle of the method
Residues of cefazolin, cefpirin, cephalexin, cefalonine, and cefquinoxime in honey, extracted with sodium dihydrogen phosphate buffer solution, purified by solid phase extraction column, determined by liquid chromatography-tandem mass spectrometry, and quantified by external standard method
.
5.
2.
5.
3 Reagents and materials
Methanol and acetonitrile: chromatographically pure; sodium dihydrogen phosphate (NaH 2 PO 4 ), sodium hydroxide, and acetic acid are analytically pure
.
5mol/L sodium hydroxide solution: Weigh 20g sodium hydroxide, dissolve it with water, and dilute to 100mL
.
0.
Standard materials: Cefazolin, Cefpirin, Cefalexin, Cefalonine, Cefquinoxime Purity ≥9%
.
1.
0mg/mL 5 kinds of cephalosporin standard stock solutions: accurately weigh each standard substance and prepare a standard stock solution with a concentration of 1.
0mg/mL with water
.
The stock solution is stored in a -18°C freezer
5 kinds of cephalosporin standard mixed working solutions: draw an appropriate amount of each cephalosporin standard stock solution as needed, and use the blank sample extract to make a matrix mixed standard working solution of appropriate concentration
.
Solid phase extraction column: OasisHLB solid phase extraction column or equivalent, 500mg, 6mL
.
Before use, it was pretreated with 5 mL methanol, 5 mL water and 10 mL sodium dihydrogen phosphate buffer solution in sequence to keep the column moist
5.
2.
5.
4 Instruments and equipment
Liquid chromatography-tandem quadrupole mass spectrometer, equipped with electrospray ion source; analytical balance: sensitivity 0.
1mg, 0.
01g; solid phase extraction vacuum device; reservoir: 50mL; micro syringe: 25μL, 100μL; scale sample Tube: 5mL, accuracy of 0.
1mL; nitrogen concentrator
.
5.
2.
5.
5 Sample pretreatment
(1) Sample preparation
For laboratory samples without crystals, stir them evenly
.
For samples with crystals, place them in a water bath of no more than 60°C under airtight conditions, warm them, shake them, stir them after all the samples have melted, and cool to room temperature
(2) Preparation of sample solution
Weigh 5g sample (accurate to 0.
01g) into a 150mL Erlenmeyer flask, add 25mL sodium dihydrogen phosphate buffer solution, dissolve the sample, mix, and adjust to pH 8.
5 with sodium hydroxide solution
.
Transfer the sample extract to the reservoir connected to the OasisHLB solid phase extraction column, and pass it through the solid phase extraction column at a flow rate of 3mL/min.
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