Two OPEEs (organic phase enzyme electrodes) used to check the percentage water content in hydrophobic foods and drugs

The development and optimization of an analytical method using enzymatic bi osensors able to operate in organic solvents [organic phase enzyme electrod es (OPEEs)] for the determination of the water content in food fats (butter , margarine) or pharmaceutical or cosmetic ointments is described. The meth od is based on the increase in enzymatic activity which is related to the i ncrease in the percentage water content in the organic phase into which the biosensor is dipped. The enzymes used to assemble the biosensors were tyro sinase or catalase, the substrates were phenol or p-cresol and tert-butyl h ydroperoxide, respectively, and the organic solvents were acetonitrile or d ioxane. A gas diffusion amperometric electrode for oxygen measurement was u sed as electrochemical transducer. The results were compared with those obt ained applying the Karl Fischer method to the same food or drug matrices. T he correlations among the two methods proved satisfactory, as the differenc e in the computed values of water content was never higher than 7%. Also, t he precision of measurements was acceptable (RSD < 6%) in all the analyses of real matrices.