Determination of β-lactam antibiotics in milk using micro-flow chemiluminescence system with on-line solid phase extraction

In this paper, a chemi luminescence (CL) micro-flow system combined with on-line solid phase extraction (SPE) is presented for determination of beta-lactam antibiotics (penicillin, cefradine, cefadroxil, cefalexin) in milk. It is based on the enhancement effect of beta-lactam antibiotics on the luminol-K3Fe(CN)6 CL system. The micro-flow system was fabricated from two polymethyl methacrylate (PMMA) plates (50 mm x 40 mm x 5 mm) with the microchannels of 200 mu m wide and 150 mu m deep. C-18-modified silica gel was packed into the microchannel (length: 10 mm., width: I mm; depth: 500 mu m) to serve as SPE device. Extraction and preconcentration of the analytes were carried out using on-line SPE micro-flow system and the selectivity of CL detection was improved. The detection limits were 0.5 mu g mL(-1) of penicillin, 0.04 mu g mL(-1) of cefradine, 0.08 mu g mL(-1) of cefadroxil and 0. 1 mu g mL(-1) of cefalexin. The proposed method was also applied to analyze the beta-lactam antibiotics in milk. Experimental results were in good agreement with those obtained by high performance liquid chromatography (HPLC) method with UV detection. (C) 2007 Elsevier B.V. All rights reserved.