Caffeine-Picrylsulfonate Liquid Membrane Electrode for Selective Determination of Caffeine in Analgesic Preparations

Article abstract of DOI:10.1021/ac00283a037

A liquid membrane electrode for caffeine prepared from a solution of caffeine-picrylsulfonate ion-pair complex in 1-octanol is developed.It exhibits Nernstian response in the range of 10^-2-10^-6 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 s to 1.5 min>, 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 μg mL^-1 of caffeine show an average recovery of 99.5percent and a mean standard deviation of 1.3percent.Determination of caffeine in some analgesic preparations gives results in good agreement with those obtained by the United States Pharmacopoela method.