1989 Volume 38 Issue 11 Pages 578-582
An immobilized salicylate hydroxylase (EC 1.14.13.1; SH) electrode (SHE) and a co-immobilized SH/laccase (EC 1.10.3.2) electrode (SHLE) were prepared by crosslinking with bovine serum albumin and glutaraldehyde on the surface of RVC (reticulated vitreous carbon) impregnated with epoxy resin. The response characteristics of these enzyme electrodes for salicylate were investigated in a phosphate buffer solution (pH 6.0) containing 1 mM nicotinamide adenine dinucleotide (reduced form). The electrode response of SHE and SHLE was measured as an anodic current of catechol produced by SH enzyme reaction and a cathodic current of ο-quinone produced by SH/laccase enzyme reaction, respectively, in a stirred solution (1430 rpm) at 30°C. Linear relationships between current response and salicylate concentration were obtained in a concentration range of 0.1100 μM for SHE and of 0.0110 μM for SHLE. The high sensitivity of the SHLE suggests the occurrence of chemical amplification (about 10 times). The enzyme electrodes were relatively stable and retained about 90% of the maximum activity even following repetitive use for more than 1 month. When not in use, they were stored in a phosphate buffer solution (pH 6.0) at 5°C. SHLE was found applicable to the determination of salicylate in pharmaceutical preparations and the results obtained were in good agreement with indicated values and those obtained by the colorimetric method.
