Determination of creatinine with a sensor based on immobilized glutamate dehydrogenase and creatinine deiminase

Abstract

Glutamate dehydrogenase and creatinine deiminase are immobilized by adsorption on wet poly(vinyl chloride) membranes. Creatinine is determined by a sensor consisting of the two membranes placed over an ammonia-sensing electrode. Endogenous ammonia is removed as it passes through the glutamate dehydrogenase layer. Creatinine (1–50 mg dl −1) is converted to ammonia in the inner creatinine deiminase layer and is detected by the ammonia electrode. The assay requires 3 min, the minimum detectable concentration is 1 mg dl −1 at pH 8.5, and the precision is ca. 5%. Endogenous ammonia can be tolerated up to 2 × 10 −4 M.