Liquid chromatographic and potentiometric methods for determinations of clopidogrel

Two different techniques are developed for the determination of clopidogrel in pharmaceutical preparations. HPLC method has been developed where chromatographic analysis is performed on Nova-Pak (R) C(18) column (3.9 mm x 150 mm, 5 mm) with an ammonium formate buffer adjusted with formic acid to pH 4.0, acetonitrile (40:60, v/v) as mobile phase, and detection at 225 rim. Good linearity (0.9993, r), accuracy (>= 99.20 \%), and precision ( <= 0.6 RSD) were obtained. Potentiometric measurments are based on tetrakis (p-chlorophenyl) borate-clopidogrel ion-pair as an electroactive material incorporating a plasticized PVC membrane with o-nitrophenyl octyl ether or dioctyl phthalate. The sensor is conditioned for at least two days in 0.1 M drug solution before use. It exhibits fast and stable Nernstian response for clopidogrel over the concentration range of 1.0 x 10(-5) similar to 1.0 X 10(-2) M and pH range of 1.5 - 4.0. Results with an average recovery of 100.6\% and a mean standard deviation of 0.86\% of the nominal were obtained. The sensor shows reasonable selectivity towards clopidogrel hydrogen sulphate in presence of many cations. No significant interferences are caused by drug excipients and diluents.