Detection of gentamicin in milk by immunoassay and flow injection analysiswith electrochemical measurement

A number of alternative approaches involving immunoassays coupled to few-in jection analysis and electrochemical detection have been evaluated with the aim of developing a simple, rapid field-based method for the quantificatio n of gentamicin in milk to within regulatory guide-line levels. Anti-gentam icin antibodies were adsorbed onto nitrocellulose and polycarbonate solid-p hase supports and positioned either in contact with flow-cell mounted elect rodes or upstream of the electrode-cell assembly. Following the competitive immunoassay, analyte levels were quantified according to the extent of glu cose oxidase enzyme label activity, measured electrochemically. The fully a ssembled flow-cell device (in situ method) was able to distinguish between 0 and 100 mug kg(-1) gentamicin in milk is. <10 min with a coefficient of v ariation value of 13.2% and with no sample pre-treatment. Performing the in cubation step outside of the flow-cell prior to cell assembly and signal me asurement required a 90 min incubation step and CV values of up to 38.7%. T he in situ assay is simple to perform, automatable and by using cheap, mass -producible screen-printed electrodes, is amenable to the development of si ngle-usage disposable measurement cartridges. (C) 2001 Elsevier Science B.V . All rights reserved.