LIQUID MEMBRANE-ELECTRODE FOR DIRECT POTENTIOMETRY AND POTENTIOMETRIC TITRATION OF STRYCHNINE

A new electrode sensitive and reasonably selective for strychnine is developed. It is based on the use of strychnine-picrolonate ion-pair complex in nitrobenzene as a liquid membrane. The electrode shows Nernstian response down to 10-5 M strychnine solutions over a pH range of 2-7 with a cationic slope of 57 mV/concentration decade. Direct potentiometric determination of samples down to 5 ppm shows an average recovery of 101.3% and a mean standard deviation of 2.4 %. Potentiometric titration with either picrolonic acid or sodium tetraphenylboron shows an average recovery of 99.1% and a mean standard deviation of 1.2%. No interferences are caused by some of the other alkaloids, and many of the substances normally occuring as natural contaminants with strychnine. © 1979, American Chemical Society. All rights reserved.