Determination of losartan and triamterene in pharmaceutical compounds and urine using cathodic adsorptive stripping voltammetry.
A square-wave voltammetric procedure for the electroanalytical determination of losartan and triamterene in Britton-Robinson buffer (pH 3.0, 0.1 mol L(-1)) as a supporting electrolyte containing 30 ng mL(-1) of copper ions was developed. Opposite to the case of triamterene, losartan can not be reduced at a mercury electrode alone, but a new peak appears at -0.25 V in the presence of copper due to the formation of a complex between copper(II) and losartan. An accumulation potential of -0.30 V during 80 s for the prior adsorption of losartan-copper(II) and triamterene on the electrode surface was used. The response of the system was found to be linear in the range of 30.0 - 270.0 nmol L(-1) for losartan and two linear dynamic ranges containing 0.5-200.0 and 200.0-400.0 nmol L(-1) of triamterene. The limits of detections were 9.7 and 0.3 nmol L(-1) for losartan and triamterene, respectively. The relative standard deviations for five replicate analyses of 100.0 and 10.0 nmol L(-1) losartan and triamterene were 5.5%. Applicability to assay the drugs in urine and pharmaceutical formulations was illustrated with satisfactory results. The direct-current polarography of triamterene indicates that the reduction of a related drug is strongly dependent on the pH of the solution. A linear segment was found with slope value of -63.6 mV pH(-1) in the pH range of 2.0 - 6.0. The stoichiometry and complex formation constant (beta) for losartan-Cu(II), number of transfer electrons (n), transfer coefficients (alpha) and number of proton transfers were also estimated.
Ensafi
Ali Asghar
AA
Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111, Iran. Ensafi@cc.iut.ac.ir
Hajian
Reza
R
D002626:Chemistry, Pharmaceutical; D003300:Copper / Q000737:chemistry; D004566:Electrodes; D006863:Hydrogen-Ion Concentration; D019808:Losartan / Q000032:analysis* / Q000652:urine; D004364:Pharmaceutical Preparations / Q000737:chemistry*; D011199:Potentiometry / Q000379:methods*; D014223:Triamterene / Q000032:analysis* / Q000652:urine
D004364:Pharmaceutical Preparations; D003300:Copper; D019808:Losartan; D014223:Triamterene