Voltammetric determination of chloramphenicol in milk at electrochemically activated carbon fibre microelectrodes

Electrochemical activation of cylindrical carbon fibre microelectrodes (CFMEs) by repetitive square-wave (SW) voltammetric scans between 0.0 and +2.6 V has shown to increase dramatically the cathodic current of chloramphenicol (CAP). This is attributed to the increase of the carbon fibre surface area due to its fracture and the appearance of deep fissures along the main fibre axis. Cyclic voltammograms of CAP suggested a contribution to the total current from most likely thin-layer electrolysis. The current density: concentration ratio calculated for the reduction of CAP at an activated fibre was 6.5 x 10(7) muA cm(-2) mol(-1) l. A method for the determination of CAP at low concentrations levels, using SW voltammetry at electrochemically activated cylindrical microelectrodes, was developed. Different chemical and electrochemical variables involved in the activation step were optimised. Calibration graphs were linear (r = 0.9990) in the 1.0 x 10(-7) to 1.0 x 10(-5) mol l(-1) concentration range, with a slope of (2.69 + 0.03) x 10(5) muA mol(-1) l. A limit of detection of 4.7 x 10(-8) mol l(-1) (15 ng ml(-1)) was found. The SWV method was applied for the determination of CAP in milk samples spiked with the antibiotic at two concentration levels: 64 and 320 ng ml(-1). Recoveries >97% were obtained in all cases by following a very simple experimental procedure. (C) 2002 Elsevier Science B.V. All rights reserved.