QUANTITATIVE-ANALYSIS OF ZOPICLONE IN TABLETS USING ION-SELECTIVE ELECTRODE AND POLAROGRAPHIC METHODS

Different types of PVC-matrix ion-selective electrodes (ISEs) that respond to the cationic form of zopiclone are described. Four ion-pairing agents, namely tetraphenylborate (TPB), reineckate (RN), phosphotungstate (PT) and silicotungstate (ST), and different plasticizers are investigated. The best PVC polymeric membrane contains nitrophenyloctylether (NPOE) as plasticizer and zopiclone-TPB as active material. This electrode exhibits a Nernstian response (60 mV per decade) in the range 1 x 10(-2) to 1 x 10(-5) M and a fast dynamic response time, this response being not affected by pH between 1.9 and 5.5. Direct potentiometry was used to determine zopiclone in drug formulations using this new zopiclone-selective electrode. The results are comparable to those obtained by differential pulse (DP)and square-wave (SW) polarographic techniques using both direct and standard addition methods.