Preparation and characterization of a new enzyme electrode based on solid paraffin and activated graphite particles

A new electrochemical biosensor was developed by incorporating an enzyme into a solid-paraffin-graphite-particle matrix. Tyrosinase served as model enzyme and the biosensor response was characterized with respect to its response to dopamine. The influence of different experimental parameters (tyrosinase loading, flow rate, oxygen dependence, pH, etc.) was investigated in order to optimize the biosensor performance. The electrode response was fast, reversible and linear in a large concentration domain (0.1 muM-1 mM). The enzyme-solid paraffin carbon paste electrode (CPE) showed markedly improved stability in flow injection analysis compared to the classical liquid paraffin-graphite-based biosensors. The biosensor allowed a sampling rate of 79 samples per hour, the repeatability of the injections was improved with respect to the classical CPE with a relative standard deviation of 2.2% (N = 63), and the detection limit for dopamine was 50 nM. The biosensor response to some phenol and catechol derivatives was also investigated.     

Evaluation of the reactivity,selectivity and lifetime of hydrotalcite-based catalysts using isopropanol as probe molecule

Hydrotalcite catalysts derived from NiAl and NiAlMg mixed oxides were successfully prepared by coprecipitation at a constant pH of 11. Physicochemical methods were investigated to determine their structural and textural properties. Using isopropanol as a probe molecule, the acid–base properties of the catalysts were investigated, and the evaluation of reactivity, selectivity and lifetime was established.