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

A number of alternative approaches involving immunoassays coupled to flow-injection analysis and electrochemical detection have been evaluated with the aim of developing a simple, rapid field-based method for the quantification of gentamicin in milk to within regulatory guide-line levels. Anti-gentamicin antibodies were adsorbed onto nitrocellulose and polycarbonate solid-phase supports and positioned either in contact with flow-cell mounted electrodes or upstream of the electrode-cell assembly. Following the competitive immunoassay, analyte levels were quantified according to the extent of glucose oxidase enzyme label activity, measured electrochemically. The fully assembled flow-cell device (in situ method) was able to distinguish between 0 and 100µgkg-1 gentamicin in milk is <10min with a coefficient of variation value of 13.2% and with no sample pre-treatment. Performing the incubation step outside of the flow-cell prior to cell assembly and signal measurement required a 90min incubation step and CV values of up to 38.7%. The in situ assay is simple to perform, automatable and by using cheap, mass-producible screen-printed electrodes, is amenable to the development of single-usage disposable measurement cartridges.