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 α-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 μg/ml (or 5-500 ng) (R 2 = 0.998). The detection limit was estimated at 0.04 μg/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.

Aminocephalosporins, Cephalexin, Mass spectrometry, Molecularly imprinted polymer, Pulsed elution, Solid phase extraction
Journal of Pharmaceutical and Biomedical Analysis
Department of Chemistry

Wu, S.G. (Stanley G.), Lai, E.P.C, & Mayer, P.M. (Paul M.). (2004). Molecularly imprinted solid phase extraction-pulsed elution-mass spectrometry for determination of cephalexin and α-aminocephalosporin antibiotics in human serum. Journal of Pharmaceutical and Biomedical Analysis, 36(3), 483–490. doi:10.1016/j.jpba.2003.05.001