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Seeds of Canavalia maritima are ground after removal of the external coat and are used for the construction of a new enzymatic electrode for urea. Aliquots (10 mg of the powder) are immobilized at the surface of an ammonia gas-sensing electrode, via glutaraldehyde or, alternatively, on PVC membranes. The analytical performance of the biosensors for serum urea determination is comparable to the spectrophotometric method.

An indirect voltammetric procedure for measuring free cyanide ions, using a chemically modified carbon-paste mercury-sensitive electrode, is described. The method is based on competitive HgII-complex formation reactions between an organic ligand at the electrode surface and CN− ions in solution. A linear decrease of the peak current of mercury in a solution of a defined Hg2+ concentration was observed, when the cyanide concentration was increased from 8.0 to 49.0 mg/L (0.3-1.9 × 10−6M). The relative standard deviation for five independent measurements was 8%.