CONSTRUCTION AND EVALUATION OF ATROPINE SELECTIVE ELECTRODES - THEIR APPLICATION TO OPHTHALMIC FORMULATIONS

Atropine selective electrodes with PVC membranes and without inner ref erence solutions were prepared, characterized and used in the analysis of pharmaceutical products. Their sensor system incorporates atropine -tetrakis(4-chlorophenyl)borate as an ionic exchanger and 2-nitropheny loctylether (Type I) or dibutylphthalate (Type II) as solvent mediator . The electrodes showed stable and rapid responses (about 6 s) for 1.2 X10(-5)-10(-1) M (Type I) and 1.4X10(-4)-10(-1) M (Type II) atropine ( ATR). A slope of about 58 mV/log[ATR] was obtained in a 2.5-9.0 pH ran ge. Both type of electrodes showed good selectivity. Their reproducibi lity was +/-1.5 mV throughout the working day. Electrodes with 2-nitro phenyloctylether as solvent mediator showed both wider linear response zone and better selectivity to sodium. Therefore they were used in di rect potentiometric determinations of atropine in ophthalmic products. The results obtained showed an average recovery of 102% and a relativ e standard deviation of +/-3%.