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 salts (AgI, Ag2S) and powdered Teflon. This membrane was incorporated in a multipurpose electrode body for batch measurements, and in a tubular flow-through sensor body for FIA measurements. For batch measurements, the equilibrium potentials recorded with continuous addition of standard penicillamine solution were considered in relation to lg (cpen / mol L-1). Linear response with slope of 60 mV was obtained in the concentration range from 2.5 × 10-5 mol L-1 to 1.8 × 10-2 mol L-1. In using the tubular sensor with a membrane of the same composi-tion 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 × 10-1 mol L-1. The response of the applied Chemical sensor to penicillamine (designated also as RSH) is explained by the formation of sparingly soluble RSAg in the reaction solution and/or on the exposed surface of the sensor. The solubility product Ks(RSAg) was determined using experimental values recorded both by batch measurements and by the continuous-flow experiment. The mean value obtained by different measurements and using a membrane of the same composition is Ks(RSAg) = (1.4 ± 0.1) x 10-20 mol2 L-2