A simple method for determination of D-penicillamine on the carbon paste electrode using cupric ions

The interaction of D-penicillamine (PA) with copper at the carbon paste electrode (CPE) in the presence of cupric ions (Cu(2+)) was used for the determination of PA at very low potential (0.1 V vs. Ag/AgCl) without applying of any modifier. The electrochemical response of copper is changed considerably in the presence of negligible amount of PA. In this report some important parameters, such as pH effect, Cu(2+) concentration and scan rate are studied, which the selected conditions were acetate buffer (pH=6) and 1 mM Cu(2+). The linear range for PA was from 1.0×10(-6) to 1.0×10(-4) M with an experimental detection limit of 1.0×10(-7) M. The relative standard deviation for 6 measurements was 3.8%. The interfering effects of some important inorganic ions were investigated, which there was no significant effect on the PA measurements. Also three organic interferences including ascorbic acid (AA), uric acid (UA) and l-cysteine (Cys) were examined, which the effect of AA was not notable, the interference of UA was moderate and for Cys was significant, but moderate at the levels which fined in the urine samples. This method was applied successfully for the determination of PA in urine sample.