Journal
MICROCHIMICA ACTA
Volume 160, Issue 4, Pages 471-475Publisher
SPRINGER WIEN
DOI: 10.1007/s00604-007-0820-1
Keywords
HPLC; cephalosporins; cefotaxime; cephalexine; solid-phase extraction; milk; veterinary formulation
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An HPLC method was developed and validated for the determination of the cephalosporins cefotaxime and cephalexine in skimmed bovine milk. The analytical column, Kromasil C-18 (250 mm x 4.0 mm, 5 mu m) was operated at ambient temperature. Mobile phase consisted of CH3OH-acetate buffer (pH = 4.0) and it was delivered isocratically at a flow rate of 1.0 mL center dot min(-1). Total analysis time was less than 5 min. Caffeine was used as internal standard (5 ng center dot mu L-1). UV detection was performed at 265 nm. Method validation was performed by means of intra-day (n = 5) and inter-day accuracy and precision (n = 8), sensitivity and linearity. Limits of detection (LOD) and limits of quantification (LOQ) were 0.1 and 0.3 ng center dot mu L-1, respectively. The method was applied to the analysis of a veterinary drug (CEPOREX) containing cephalexine. The results were quite accurate with the relative error varying from -8.0 to -3.5%. Solid-phase extraction was applied to remove all matrix interference from milk samples. High extraction recoveries (average 84-121%) were achieved by using Abselut NEXUS cartridges with acetonitrile as eluent and a rinsing step with water and n-butanol. A pre-concentration step was necessary in a 1/10 level to reach the EU MRL concentration level (100 mu g center dot kg(-1)). RSD values were less than 7% for both cephalosporins.
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