Abstract: The development and characteristics of a reagentless amperometric organic phase enzyme electrode (OPEE) employing covalently attached horseradish peroxidase and an electrochemically deposited ferrocene-modified polyaniline film on a glassy carbon electrode is reported. The covalent attachment of ferrocene to an electrochemically deposited insoluble polymer film provided a mechanism of preventing the leaching of ferrocene into the predominantly organic solvents, required for construction of reagentless OPEE. Hydrodynamic voltammetry studies showed that the response of the OPEE to hydrogen peroxides increased at higher cathodic potentials; however, interference due to molecular oxygen also increased. Interference of molecular oxygen was minimized when the OPEE was operated at an applied potential of -50 mV (or less negative) vs Ag/AgCl. The cathodic response of the OPEE was found to increase steeply when the aqueous buffer content of the acetonitrile was increased from 0 to 5 and then plateau with no further increase when the buffer content was increased to 30. The dynamic properties of this enzyme electrode were exploited for the detection of micromolar concentrations of different peroxides in flow injection analysis where the sensitivity trend was lauroyl peroxide > hydrogen peroxide > 2-butanone peroxide > cumene hydroperoxide > tert-butyl hydroperoxide. Applicability of the enzyme electrode for measurement of peroxide in real sample was demonstrated. Copyright 1995, American Chemical Society.

Abstract: A flow-through arrangement of thermistors for detecting heat changes due to chemical reactions was included in a flow injection system. Changes of 0.001°C could be measured reproducibly. Working ranges of analyte concentration. depended on reaction enthalpy and varied from 1 mM to 10 M for acids and bases and 10 to 1000 ppm for, e.g., alkylhydroperoxides. Typical signals are presented for NaOH (reaction with HCl), Ca(II) (EDTA determination), H2O2, t-butyl hydroperoxide and cumyl hydroperoxide (SO2 reduction in presence of amine).

Abstract: A reliable and sensitive stopped-flow injection method is described for the determination of hydrogen peroxide, cumene hydroperoxide and tert-butyl hydroperoxide. It is based on the oxidation of leuco-phloxin to the fluorescent phloxin by hydroperoxide and haematin. Linear calibration graphs were obtained between 4 times 10^-6 and 8 times 10^-5 M, with a sampling-rate of 25 samples h-1. The detection limit, defined as three standard deviations of the reagent blank, was 1.5 times 10^-7 M. The usefulness of the method was tested in the determination of lipohydroperoxides in six commercial oil samples and of hydrogen peroxide in six milk samples of different levels of skimming. The results agreed closely with those obtained by the iodometric method.