RELIABLE AMPEROMETRIC DETERMINATION OF GLYCEROL AND GLYCEROL-3-PHOSPHATE WITH A BIENZYMATIC NYLON MEMBRANE-ELECTRODE

An enzymatic biosensor for glycerol and glycerol-3-phosphate was designed, based on the co-immobilization of two enzymes, glycerol kinase and glycerol-3-phosphate oxidase, on a nylon membrane activated by a process recently reported for nylon balls. Optimum conditions for immobilization, use and storage were defined. A detection limit as low as 7 x 10(-8) M for glycerol and 1 x 10(-7) M for glycerol-3-phosphate was obtained and assays could be performed in the linear ranges 1 x 10(-7)-5 x 10(-4) and 2 x 10(-7)-2 x 10(-3) M for glycerol and glycerol-3-phosphate, respectively. The response time is < 3 min. No significant difference in the sensitivity was found after 7 h of continuous use and 75% of the initial sensitivity was maintained after 50 days of storage at 4-degrees-C. The electrode was tested with various samples such as standard serum and standards of di- or triglycerides and the results were in good agreement with the theoretical values.