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6.
2.
2.
1 Scope of application
It is suitable for the determination of lincomycin , erythromycin , spiramycin , tilmicosin , tylosin , josamycin , kitasamycin , and oleandomycin residues in honey by liquid chromatography-tandem mass spectrometry
.
The detection limit of the method is 2.
6.
2.
2.
2 Principle of the method
Residual lincomycin, erythromycin, spiramycin, tilmicosin, tylosin, josamycin, kitasamycin, and oleandomycin residues in honey Tris (Tris) Buffer solution (pH=9) is extracted, filtered, purified by OasisHLB solid phase extraction column, eluted with methanol and evaporated to dryness, the residue is dissolved in acetonitrile- 0.
01mol/L ammonium acetate solution, after passing through a 0.
2um filter membrane, the sample solution For liquid chromatography-tandem mass spectrometer determination, internal standard method for quantification
.
6.
2.
2.
3 Reagents and materials
Methanol, acetonitrile: chromatography; Tris (Tris), calcium chloride (CaCI2 2 · 2H 2 O), ammonium acetate, hydrochloride: pure class distinctions
.
Eluent: methanol solution (2+3, v/v)
.
Measure 40mL methanol and mix with 60mL water; 0.
The purity of the standard material is ≥99%
.
0.
1mg/mL standard stock solution: accurately weigh the appropriate amount of each standard substance, and use methanol to prepare a standard stock solution of 0.
1mg/mL
.
The solution is stored at 4°C
0.
1mg/mL Roxithromycin and Clindamycin internal standard stock solution: accurately weigh appropriate amount of Roxithromycin and Clindamycin standard substances, and mix with methanol to make a 0.
Matrix standard working solution: draw different volumes of mixed standard working solution and 20μL mixed internal standard working solution, and use blank sample extract to make 2.
0ng/mL, 5.
0ng/mL, 10.
0ng/mL, 20.
0ng/mL, 50.
0ng/ mL of matrix standard working solutions of different concentrations
.
Prepared on the same day
OasisHLB solid phase extraction column or equivalent: 200mg, 6mL
.
Before use, activate with 5mL methanol and 10mL water in sequence to keep the column moist
6.
2.
2.
4 Instruments and equipment
Liquid chromatography-tandem mass spectrometer: equipped with electrospray ion source; analytical balance: sensitivity 0.
1mg and 0.
01g; nitrogen concentrator; liquid mixer; reservoir: 50mL; vacuum pump: maximum negative pressure 80kPa; solid phase Extraction device; blow-drying tube: 10mL
.
6.
2.
2.
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) Extraction
Weigh 2g sample, accurate to 0.
01g
.
Place it in a 150mL Erlenmeyer flask, add 20μL of mixed internal standard working solution, add 25mL Tris buffer solution, and mix quickly on a liquid mixer for 1 minute to completely dissolve the sample
(3) Purification
Connect the glass reservoir stuffed with glass wool to the OasisHLB solid phase extraction column, pour the sample solution into the glass reservoir, adjust the flow rate to less than 3mL/min, wait for the sample solution to flow out completely, use 5mL water and 5mL in turn The eluent washes the column and discards all the effluent
.
Drain under reduced pressure for 20 min, and then eluted with 5 mL methanol.
Collect the eluate in a 10 mL blow-drying tube
.
Blow dry at 50°C with a nitrogen concentrator
.
Accurately add 1.
0mL constant volume solution to dissolve the residue, and after passing through a 0.
2um filter membrane, it is used for liquid chromatography-tandem mass spectrometry determination
.
According to the above operation steps, prepare the sample blank extract for preparing the series of matrix standard working solutions
.