Preparation of Caffeine-Ion Selective Electrode and Its Application to Determination of Caffeine in Coke Drink

An ion selective electrode (ISE) using the association complex of caffeine with molybdophosphoric acid as electroactive substance was prepared. It was found that this ISE behaved with excellent selectivity and characteristic potential response toward caffeine. Nernst potential response was obtained in the range of 5×10-6-1.0×10-2mol·L-1 with slop of 51.4 mV·pc-1 in PBS of pH 2.54. Recovery was tested by standard addition method using samples of coke drink as matrixes, values of recovery found were in the range of 98.4%-102.4%.