Determination of penicillamine by batch and flow-injection potentiometry with AgI-based sensor

Potentiometric determination of penicillamine (pen) is described based on a batch experiment and flow-injection analysis (FIA) using a chemical sensor with AgI-based membrane. The membrane was prepared by pressing silver salt s (AgI, Ag2S) and powdered Teflon. This membrane was incorporated in a mult ipurpose electrode body for batch measurements, and in a tubular flow-throu gh sensor body for FIA measurements. For batch measurements, the equilibriu m potentials recorded with continuous addition of standard penicillamine so lution were considered in relation to lg (c(pen)/mol L-1). Linear response with slope of 60 mV was obtained in the concentration range from 2.5 x 10(- 5) mol L-1 to 1.8 x 10(-2) mol L-1. In using the tubular sensor with a memb rane of the same composition for FIA measurements, the linear response with slope of 59 mV was recorded in the concentration range from 1 x 10(-4) mol L-1 to 1 x 10(-1) mol L-1. The response of the applied chemical sensor to penicillamine (designated also as RSH) is explained by the formation of spa ringly soluble RSAg in the reaction solution and/or on the exposed surface of the sensor. The solubility product K-s(RSAg) was determined using experi mental values recorded both by batch measurements and by the continuous-flo w experiment. The mean value obtained by different measurements and using a membrane of the same composition is K-s(RSAg) = (1.4 +/- 0.1) x 10(-20) mo l(2) L-2.