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A biosensor was developed by immobilizing laccase onto mercury thin film electrode (MTFE) by means of gelatin that is then crosslinked with glutaraldehyde. Mercury thin film (MTF) was deposited onto glassy carbon electrode (GCE) and the obtained biosensor was utilized for the determination of phenolic compounds. The measurement was based on the amperometric detection of oxygen consumption in relation to analyte oxidation. The optimum experimental conditions for the biosensor were investigated and the system was calibrated for both catechol and phenol. A linear relationship between sensor responses and analyte concentrations was obtained in concentration range between 0.5 × 10 -6 – 5.0 × 10 -6 M for catechol and 2.5 × 10 -6 – 2.0 × 10 -6 M for phenol, respectively. Mercury thin film was also formed onto the surface of screen printed graphite electrodes and applied for the catechol detection. The linearity was observed in concentration range between 2.5 × 10 -6 – 3.0 × 10 -5 M. [ABSTRACT FROM AUTHOR]

A disposable tyrosinase biosensor has been developed for the analysis of phenols and polyphenols, by modifying screen printed electrodes (SPEs) with addition of suitable mediators of redox processes directly into the conductive pastes. The percent ratio of mediator in the pastes was chosen depending on the electrochemical sensitivity either in batch or standard flow conditions. Ferrocene modified carbon electrodes have been used on whose surface the enzyme tyrosinase was immobilized in a glutaraldehyde cross-linked matrix of bovine serum albumin. Mixing the mediator to the electrode pastes should overcome transport limitations, due to its dissolution, which occur in commonly used immobilization procedures. Different immobilization techniques of tyrosinase on SPEs in the detection of phenolic compounds were tested and compared. Modified SPEs showed relatively good reproducibility and detection limits in the micromolar range for all phenolic compounds used. Major sensor parameters have been optimized in flow systems putting special attention on operating potential, pH and buffer composition, which strongly affect the detection of polyphenols and operational stability in wine. The resulting biosensors were stored and dried for a minimum of 8  h at 4°C, and showed a shelf stability of about 30 days. The procedure has been applied both on a synthetic wine matrix and on real samples, to determine the ‘pool’ of phenolic composition in terms of phenol concentration. [ABSTRACT FROM AUTHOR]

A microbial biosensor was developed for the determination of phenolic compounds and the measurement was based on oxygen consumption in relation to analyte oxidation. Induced cells of Pseudomonas putida DSM 50026 were immobilised on the surface of SPG electrodes covered with cellulose acetate membrane by means of gelatine which was then cross linked with glutaraldehyde. The systems were calibrated for different phenolic substances. Detection ranges were 0.1–1.0 μM for phenol and 0.05–1.0 μM for l-tyrosine and l-DOPA, respectively, with a response time of 3 min. Furthermore, phenol detection was performed in the presence of synthetic wastewater samples. [Copyright &y& Elsevier]