RELATIVE SELECTIVITY COEFFICIENT AS A NEW CONCEPT FOR EVALUATING ELECTROCHEMICAL DOPAMINE SENSORS

Two types of electrochemical sensor were introduced for the selective determination of dopamine.Both potassium Tetrafloropheny1 borate (K-TFPB) and a synthesized N, Ñ-bis-ethoxycarbonyl-1, 10-diaza-4, 7, 13, 16-tetraoxacyclo-octadecane (DZCE (were used as charged ionophore and a neutral carrier. The calibration graphs of the obtained electrodes showed satisfactory Nernstian slopes (57.8, 58.4 mV/decade). They work linearly 9 x 10^-3-7.9 x 10^-6 M DAH⁺ within a pH value 3.5-8.3 for both electrodes. Selectivity coefficients of the studied electrodes were calculated towards several inorganic cations, aminoacids, and pharmaceutical compounds The Relative Selectivity Coefficient (RSC) was introduced and was applied for evaluating the selectivity properties of dopamine electrode using mathematical equation. Average Relative Selectivity Coefficient (ARSC) and Total Average Relative Selectivity Coefficient (TARSC) were defined and calculated as new parameters for each electrode. An improvement of the selectivity coefficient values was observed when DZCE was added as neutral carrier to the membrane constituents. The electrode was applied for the determination of dopamine in its pharmaceutical preparations and in banana pulp. The obtained results were compared with those obtained by a previously reported spectrophotometric method.