Spectrofluorometric determination of alpha-aminocephalosporins in biological fluids and pharmaceutical preparations

A selective and highly sensitive fluorometric method was developed for the determination of four alpha-aminocephalosporins, namely cefaclor, cefadroxi l, cephalexin and cephradine. The method involves the reaction of the targe t compounds with fluorescamine at a specific pH, ranging from 7.8 to 8.4. T he produced derivatives exhibit maximum fluorescence intensities at 472-478 nm after excitation at 370-372 nm. The method is highly specific because o ther alpha-aminocephalosporins whose alpha amino group was blocked do not r eact similarly and hence do not interfere. At the specific pH range of the reaction where no degradation may occur with that medium the proposed metho d can be utilised as a stability-indicating assay. The different experiment al parameters affecting the derivatisation reaction were carefully studied and incorporated into the procedure. Under the described conditions, the pr oposed method is linear over the concentration range of 0.05-1 mu g ml(-1) for both cefaclor and cephalexin, and 0.05-0.65 and 0.025-0.5 mu g ml(-1) f or cefadroxil and cepharadine, respectively and the coefficients of determi nation were greater than 0.999 (n = 3). The recoveries of the title compoun ds from spiked serum ranged from 88.6 to 89.7% and from spiked urine from 9 2.2 to 93.3% with a limit of quantitation (LOQ) of 25-50 ng ml(-1) and limi t of detection (LOD) of 5 ng ml(-1) (S/N = 2) for all drugs. The mechanism of the fluorometric reaction is proposed and the advantages of the proposed method are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.