Amino derivatives of biphenyl have been proven to be genotoxic and/or carcinogenic, thus they are widely monitored in the environment as well as in biological liquids. This study was devoted to HPLC determination of 2-aminobiphenyl, 3-aminobiphenyl, and 4-aminobiphenyl in model drinking and river water samples using amperometric detection in a thin layer cell with boron doped diamond thin film electrode. Satisfactory separation of studied analytes was achieved at a ChiraDex column (Merck, Germany) with chemically bonded b-cyclodextrin in a mobile phase aqueous buffer/acetonitrile/methanol (40/30/30, v/v/v) with total separation time of six minutes. The highest detector response with satisfactory repeatability (relative standard deviation < 2.9% for all aminobiphenyls) was obtained using 0.01 mol L À1 acetate buffer at pH 5.0 as an aqueous component of the mobile phase. For direct determination of aminobiphenyls in drinking and river water model samples limits of quantitation ca. 4 Â 10 À7 mol L
À1were achieved. Applying off-line solid phase extraction using Lichrolut EN (Merck, Germany) cartridges and elution by diethyl ether, limits of quantitation were lowered down to the 10 À9 mol L À1 concentration range.
The performance of a microcrystalline boron-doped diamond electrode in a thin-layer and wall-jet amperometric detection cell for HPLC was compared with the spectrophotometric detection. Comparison of peak parameters of 2-, 3-, and 4-aminobiphenyl after their separation revealed satisfactory repeatabilities of signal responses for all detection modes and regarding electrochemical detection higher current densities and higher noise for the thin-layer arrangement, and a slightly wider linear dynamic range of calibration dependencies and lower quantitation limits in the 10 À8 mol L À1 concentration range for the wall-jet arrangement. This detection mode was further employed for the determination of studied aminobiphenyls in model samples of the synthetic colorant tartrazine. Using solid phase extraction for the preliminary separation and preconcentration of the analytes the limit of quantitation was lowered to nanomolar concentrations.
A biosensor for putrescine containing a sensing layer with an optical oxygen probe based on ruthenium complex and the enzyme diamine oxidase from pea is described. The diamine oxidase was pre-immobilised on broken micro-beads modified with a ferrofluid. The pre-immobilised enzyme and ruthenium complex were both incorporated into the UV-cured inorganic-organic hybrid polymer ORMOCER and deposited on a lens to form a sensitive layer of 210 µm in thickness. The sensitivity to the putrescine concentration determined under air saturation was between 3.50 µs L mmol −1 and 4.50 µs L mmol −1 in a hundred experiments conducted intermittently over a one year period. With the oxygen concentration increasing from 10 % to 100 % of DO (dissolved oxygen), the biosensor sensitivity decreased from 6.87 µs L mmol −1 to 0.70 µs L mmol −1 and its dynamic range increased from 0.10 mmol L −1 to 1.75 mmol L −1 . To estimate the behaviour of the putrescine sensor in parametric space, a mathematical model of the reaction-transport processes inside the sensing layer was developed. The model revealed the qualitative relations between the sensor analytical features, the characteristics of the sensitive layer and concentrations of substrates. The results of the mathematical modelling may serve as guidelines in the design of optodes for specific applications.
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