Gallamine-tetraphenylborate-modified carbon paste electrode for the potentiometric determination of gallamine triethiodide (flaxedil).

The construction and general performance of a novel modified carbon paste electrode for the determination of gallamine triethiodide have been developed. The electrode shows a stable, potentiometric response for gallamine in the concentration range 1 x 10(-3)-2 x 10(-6) M at 25 degrees C independent of pH in the range 5-8. The electrode passes a near-Nernstian cationic slope of 17.0+/-0.7 mV and lower detection limit of 1 x 10(-6) M with a fast response time of 20-45 s. Selectivity coefficients for gallamine relative to a number of interfering substances were investigated. There is a negligible interference from the studied cations, anions, and pharmaceutical excipients. The determination of gallamine in aqueous solution shows an average recovery of 99.5% and a mean relative standard deviation (RSD) of 1.4% at 100 microg/ml. The direct determination of gallamine in injection solution gave results that compare favorably with those obtained by the British pharmacopoeia method. Potentiometric titration of gallamine with sodium tetraphenylborate and phosphotungstic acid as a titrant has been monitored with the modified carbon paste electrode as an end-point indicator electrode.