Urate oxidase electrode based on dissolved oxygen probe for urine uric acid determination.

A biosensor for the specific determination of uric acid in urine was developed using urate oxidase (EC 1.7.3.3) in combination with a dissolved oxygen probe. Urate oxidase was immobilized with gelatin by means of glutaraldehyde and fixed on a pretreated teflon membrane to serve as enzyme electrode. The electrode response was maximum when 50 mM glycine buffer was used at pH 9.2 and 35 degrees C. The enzyme electrode response depends linearly on uric acid concentration between 5-40 microM with a response time of 5 min. The enzyme electrode is stable for more than 2 weeks and during this period over 35 assays were performed.

Eggplant tissue homogenate-based bioselective membrane electrode for determination of catechol.

A novel eggplant tissue homogenate-based membrane electrode with high selective response to catechol (5 x 10(-6)-2.5 x 10(-5) M concentration) has been constructed by immobilizing tissue of eggplant (Solanum melangena L.) at dissolved oxygen probe. In order to optimize the stability of the electrode, general immobilization techniques are used to secure the eggplant tissue section physically in a gelatin-glutaraldehyde cross-linking matrix. The electrode response was maximum when 50 mM phosphate buffer was used at pH 7.0 and 35 degrees C. The sensor is stable for more than 3 months.

Enzyme electrode based on oxalate oxidase immobilized in gelatin for specific determination of oxalate.

A biosensor for the specific determination of oxalate was developed using oxalate oxidase (EC 1.2.3.4) from barley (Hordeum vulgare) seedling roots in combination with a dissolved oxygen probe. Oxalate oxidase immobilized with gelatin using glutaraldehyde and fixed on pretreated teflon membrane served as an enzyme electrode. The electrode response was maximum when 50 mM succinate buffer was used at pH 3.2 and 35 degrees C. The biosensor response depends linearly on oxalate concentration between 5 x 10(-6)-2 x 10(-4) M with response time 30 sec and substrate specificity of the oxalate oxidase electrode of 100%. The sensor is stable for more than 3 months during which time more than 400 assays can be performed.