A New Liquid Membrane Electrode For Selective Determination Of Caffeine

Abstract

A new liquid membrane electrode for caffeine prepared from a solution of caffeine-picrylsulfonate ion-pair complex in n-octanol is developed. It exhibits Nernstian response in the range of 10'2 to lO^M caffeine with a cationic slope of 59 mV/concentration decade. The electrode has a wide working pH range (5.5 -9.5), fast response time (20 seconds - 1.5 minutes), stable response for at least 30 days and high selectivity for caffeine in the presence of many organic bases. The results obtained for quantitation of 1 - 1000 jiig ml"' of caffeine show an average recovery of 99.5% and a mean standard deviation of 1.3%.