Selective membrane electrode potentiometry and spectrophotometry of a photochemical reaction of thioredazine hydrochloride.

A PVC membrane electrode of the coated wire type was prepared which is selective for thioredazine. It showed a Nernstian response over a thioredazine concentration range 6.3 x 10(-6) to 2.5 x 10(-3) M, at 25 degrees C, and was selective, precise, and usable within the pH range 2.1-7.0. The standard electrode potentials, E degrees, were determined at different temperatures and used to calculate the isothermal temperature coefficient of the electrode. The photoreaction occurring in thioredazine solution exposed to daylight did not affect the electrode performance. This reaction was investigated kinetically to determine its rate constant and half-life at different temperatures.

Hydralazine-selective PVC membrane electrode based on hydralazinium tetraphenylborate.

A hydralazine ion-selective PVC membrane electrode based on hydralazinium tetraphenylborate has been prepared with dioctyl phthalate as plasticizer. The electrode showed linear response with a slope factor of 57.5 mV/concentration decade at 20 degrees over the concentration range from 4 x 10(-4) to 10(-1)M hydralazine. The effects, on the electrode performance, of membrane composition, pH of the test solution and the time of soaking were studied. The electrode exhibited good selectivity for hydralazine with respect to a large number of inorganic cations and organic substances of biological importance. The standard-addition method and potentiometric titrations were used to determine hydralazine concentrations in pure solutions and in a pharmaceutical preparation, with satisfactory results.