engleski

Oxytetracycline Determination in Food Samples Using Poly(L-histidine)-Cu Modified QCM Pt Electrode

Introduction: Tetracyclines are traditionally used for the treatment of infectious diseases in animals and may contaminate animal derived food such as honey, milk, meat and dairy product. This work describes flow injection method for determination of tetracyclines as the result of their complexing to the surface of Pt electrode modified with Cu-poly(L-histidine) layer using quartz crystal microbalance (QCM) as measuring device. Methods: Potentiostat 264 A (Princeton Applied Research, USA) was used for CV measurements. Frequency Response Detector model 1025 (PAR, USA) was added to previous configuration for EIS measurements. QCM digital controller model QCM200 (Stanford Research Systems, USA) was used for monitoring of electropolymerization (from L-histidine solution, pH = 9.0) and analytical measurements. All electrochemical measurements were carried out in a three-electrode cell: Pt disc as working electrode, Pt plate and saturated calomel electrode (SCE) as counter and reference electrodes, respectively. Results: Electropolymerization of the L-histidine on platinum surface of piezoelectric quartz crystals resulted in formation of stable poly(L-histidine) layer. Surface structuring was monitored using EIS and CV in the presence of [Fe(CN)6]4-/[Fe(CN)6]3- redox couple in phosphate buffer pH=3.0 and pH=9.0. In situ monitoring of poly(L-histidine) layer growth was performed using QCM and CV. After addition of copper a Cu-poly(L-histidine) complex was formed and thus a sensitive area capable for further biocomplexing with different bioligands was prepared. Measuring setup for analytical studies consisted of QCM and a flow-through system (FIA). Discussion: Oxytetracycline, as tested analyte, exhibits high binding affinity to transition metals and was successfully bound to Cu–poly(L-histidine) complex. The presence of oxytetracycline was detected in solution in the range between 0.4 and 500 µg/mL and measured in different food samples. Flow-injection method allows different types of samples to be analysed automatically at a rate of six samples per hour.

Oxytetracycline; Cu-poly(L-histidine); QCM

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