Determination of urate in undiluted whole blood by enzyme electrode

An amperometric enzyme electrode is described for the assay of urate in undiluted, unstirred whole blood. The electrode used Aspergillus flavus uricase (EC.1.7.3.3) cross-linked to bovine serum albumin by means of glutaraldehyde, sandwiched between a dimethyldichlorosilane-treated microporous polycarbonate membrane and an inner cellulosic H2O2-selective membrane. The resulting device had a low pH dependence, was capable of repeated use in blood, and gave an acceptable correlation with a standard spectrophotometric method. Electrode steady state and dynamic response were found to be dependent upon the amount of enzyme loading, and could be further optimised by the incorporation of catalase in the enzyme layer.