Molecularly imprinted solid phase extraction-pulsed elution-mass spectrometry for determination of cephalexin and α-aminocephalosporin antibiotics in human serum

A highly selective molecularly imprinted solid phase extraction (MISPE)-pulsed elution (PE) method Coupled with electrospray mass spectrometry (MS) was developed for the rapid screening and determination of cephalexin in alpha-aminocephalosporin antibiotics. This method involved the solid phase extraction of cephalexin using a molecularly imprinted polymer micro-column, and pulsed elution with 1% trifluoroacetic acid in methanol, which contains sulindac as an internal standard for enhanced precision in MS detection. An LC/MS spectrometer was operated in the positive electrospray mode, and the selected-ion-recording (SIR) function was employed to detect the molecular ions of cephalexin, cefradine, cefadroxil and sulindac at m/z, 348, 350, 363 and 357. Linearity was achieved in the cephalexin concentration range from 0.3 to 25 mug/ml (or 5-500 ng) (R-2 = 0.998). The detection limit was estimated at 0.04 mug/ml (or 0.8 ng) of cephalexin. Advantages of the newly developed MISPE-PE-MS, over the previously reported MISPE-DPE-FPE-UV, were evidenced in terms of detection limit, analysis time, solvent consumption, and simplicity of method development. (C) 2004 Elsevier B.V. All rights reserved.