Assay of terfenadine in pharmaceutical formulation and human plasma by adsorptive stripping voltammetry

The controlled adsorptive accumulation of Zn(II)-terfenadine complex (1:1) onto a hanging mercury drop electrode (HMDE) provides the basis for determination of the antihistamine drug terfenadine by differential pulse cathodic adsorptive stripping voltammetry. The adsorbed Zn(II)-terfenadine complex (1:1) at the HMDE developed a stripping voltammetry peak at more negative potential than that of the free Zn(II) ions. The peak current was used for the determination of terfenadine in pharmaceutical formulation and human plasma in 0.1 mol l(-1) sodium perchlorate solution under the optimized conditions (E(acc), -0.5 V; t(acc) 360 s; scan rate, 5 mV s(-1) and pulse height 100 mV). The developed peak current (i(p)) showed a linear dependence with terfenadine concentration within the range of 6 x 10(-8) - 9 x 10(-7) mol l(-1). The recoveries were found 98.97-99.35%, 99.72-99.02% and 100.58-101.08% with the R.S.D. 0.16-0.27%, 0.25-0.82% and 0.44-1.14% in authentic form, pharmaceutical formulations and human plasma, respectively. The detection limits were 0.4505 and 0.6115 ng ml(-1) terfenadine in pharmaceutical formulations and human plasma, respectively.