The potential role of biosensors in the food and drink industries.

Despite their apparent potential as analytical tools in the food and drink industries, only a few biosensors are used routinely. This article describes the development of biosensors for these sectors and discusses the technical and economic problems of applying this technology to the monitoring of food and drink products.

Detection of the cyclic nitramine explosives hexahydro-1,3,5-trinitro- 1,3,5-triazine (RDX) and octahydro- 1,3,5,7-tetranitro- 1,3,5,7-tetrazine (HMX) and their degradation products in soil environments.

The cyclic nitramine explosives hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazine (HMX) were examined in field and microcosm soil samples to determine their patterns of degradation and environmental fates. A number of analytical techniques, including solid-phase microextraction with on-fiber derivatization, gas chromatography-mass spectrometry, gas chromatography with electron-capture detection, liquid chromatography-mass spectrometry, and micellar electrokinetic chromatography were required for the analyses. Two different classes of intermediates were detected, both of which lead ultimately to the formation of nitrous oxide (N2O) and carbon dioxide (CO2). The first class was identified as the nitroso derivatives formed by the sequential reduction of -NO2 functional groups. The second class of intermediates, which was favored at higher humidities and in the presence of anaerobic sludge amendments, consisted of ring cleavage products including bis-(hydroxymethyl)-nitramine and methylenedinitramine. Rye-grass (Lolium perenne) present in field samples was found to extract and accumulate HMX from soil without further degradation. In all cases (excepting the plant samples), the indigenous microbes or amended domestic anaerobic sludge consortia degraded the cyclic nitramine explosives eventually to produce N2O and CO2.

Sulfobutylether-beta-cyclodextrin-mediated capillary electrophoresis for separation of chlorinated and substituted phenols.

Cyclodextrin-mediated capillary electrophoresis has been developed for separation and analysis of chlorinated as well as substituted phenolic compounds. The procedure used a negatively charged sulfobutylether-beta-cyclodextrin (SB-betaCD) to effect differential partitioning of the phenols between the buffer and CD phases. In 50 mM phosphate buffer containing as low as 1 mM SB-betaCD, 25 phenolic compounds including 11 Environmental Protection Agency (EPA) priority phenols were separated with theoretical plate numbers well above 100,000, for 50 cm of effective length in most cases. An equilibrium complexation model was used for investigating the effect of pH as well as different cyclodextrin concentrations on the electrophoretic mobility. The cyclodextrin-mediated capillary electrophoresis system was also applicable for separating and quantifying the level of pentachlorophenol in contaminated soil samples.

Dual functionalities of 4-aminodiphenylamine in enzymatic assay and mediated biosensor construction.

4-Aminodiphenylamine (N-phenyl-1,4-phenylenediamine, CAS 101-54-2) and its water-soluble HCl salt (CAS 2198-59-6) were demonstrated to be efficient mediators for glucose oxidase, lactate oxidase, xanthine oxidase, and lysine oxidase. Using cyclic voltammetry, single oxidative peak potentials were observed for scans ranging from 0 to 0.5 V vs Ag/AgCl. The half-wave potential for both preparations was 0.11 V vs Ag/AgCl at pH 7 and decreased 59 mV per unit pH increase. Peak current data were analyzed to estimate diffusivities of 0.8 x 10(-5) cm2/s for soluble 4-ADPA HCl, and 2.36 x 10(-5) cm2/s for 4-ADPA solubilized in 2.5 mM 2-hydroxypropyl-beta-cyclodextrin. The overall second-order kinetic constants (k) for the reaction of reduced glucose oxidase with oxidized 4-ADPA HCl and 4-ADPA in cyclodextrin were estimated to be 1.8 x 10(5) and 1.7 x 10(-5) M-1 s-1, respectively, using cyclic voltammetry measurements at varied scan rates and enzyme concentrations. Both preparations proved to be suitable electron acceptors for horseradish peroxidase, as indicated by changes in absorbance spectra upon oxidation or reduction. The electrochemical and spectral behavior of the preparations were applied in conjunction with glucose oxidase to devise mediated amperometric and hydrogen peroxide-coupled spectrophotometric assays for glucose. The results of both assays compared favorably with the hexokinase reference method.