Electrochemical behavior and determination of amiloride drug in bulk form and pharmaceutical formulation at mercury electrodes.

The polarographic behavior of amiloride hydrochloride has been studied in Britton-Robinson buffers of pH 1.9-11. In acidic medium at Ph< or =2, the dc-polarograms exhibited a single 4-electron cathodic irreversible wave, while at pH values >2, a second two-electron irreversible cathodic wave appeared at a more negative potential. The single or first wave may be attributed to the cleavage of the double bond of the -CH=NH of the imidino amide group with the release of NH(3). While the second wave may be due to the saturation of the C=O of the carboxamide moiety. A polarographic procedure of suffocate sensitivity for the determination of bulk amiloride drug in Britton-Robinson buffer at pH 2 is described. The calibration graph was obtained over the concentration range 2.5 x 10(-5) to 2.5 x 10(-4) M amiloride. The limits of detection (LOD) and quantitation (LOQ) of the procedure were 1 x 10(-5) and 3.3 x 10(-4) M bulk amiloride, respectively. Moreover, a differential-pulse adsorptive cathodic stripping voltammetric procedure has been described to assay of the drug at lower concentration levels. The optimal conditions were: E(acc) = -0.9V, t(acc)=30 s, scan rate=20mV, pulse-height=90 mV and Britton-Robinson buffer of pH 8. The calibration graph was obtained over the concentration range 2 x 10(-8) to 1 x 10(-6) M for bulk amiloride. Both procedures were successfully applied to the determination of amiloride in tablets without the necessity for sample pretreatment or any time-consuming extraction or evaporation steps prior to the drug analysis.

Square-wave adsorptive cathodic stripping voltammetric determination of anti-inflammatory indomethacin drug in tablets and human serum at a mercury electrode.

Indomethacin is a non-steroidal anti-inflammatory drug possessing anti-pyretic and analgesic properties. A fully validated square-wave adsorptive cathodic stripping voltammetric procedure is described for determination of indomethacin. The procedure was based on the reduction of the C=O double bond of the drug molecule in Britton-Robinson buffer (pH 4) after its preconcentration onto the mercury electrode surface. The optimized conditions of the procedure were: frequency 120 Hz, scan increment 10 mV, pulse amplitude 50 mV, preconcentration potential -0.9 V (vs. Ag/AgCl/KCl(s)) and preconcentration time 90 s. The proposed procedure was successfully applied for determination of the drug in tablets and human serum with good recoveries. The limits of detection in bulk form and human serum were 6.7 x 10(-10) mol L(-1) and 8.1 x 10(-10) mol L(-1), respectively.

Charge transfer complexes of methylnaphthalene derivatives with TCNE in CCl4.

The spectrophotometric and thermodynamic properties of different substituted methylnaphthalenes charge transfer (CT) complexes with tetracyanoethylene have been studied in carbon tetrachloride. The spectral characteristics of the CT bands have also been discussed in relation to the positions of methyl groups. The formation constants and the spectral properties of the complexes are markedly affected with the substitution position of the methyl groups. The ionization potentials of the donors are determined.