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Abstract: The electrochemical behavior of glipizide at the hanging mercury drop electrode (HMDE) was studied in B–R universal buffers of pH 1.7–11. The voltammograms exhibited a well-defined 4-electron irreversible cathodic peak which attributed to reduction of the two Cbonds of the pyrazine ring of glipizide molecule. Glipizide was found to has an interfacial adsorptive character onto the mercury electrode surface. A monolayer surface coverage of 1.02×10−10 molcm−2 was estimated and hence each adsorbed glipizide molecule occupied an area of 1.63nm2 onto the mercury electrode surface. A simple and precise square-wave adsorptive cathodic stripping (SWAdCS) voltammetric procedure was described for quantification of bulk glipizide with a limit of detection of 1.5×10−10 M and a limit of quantitation of 5×10−10 M. The proposed procedure was successfully applied for quantitation of glipizide in its pharmaceutical formulation (Minidiab tablets) without interference from excipients. [Copyright &y& Elsevier]

Abstract: The electroreduction of ethinylestradiol at the hanging mercury drop electrode in the Britton–Robinson universal buffer of pH 2–11 was studied and its interfacial adsorptive character onto the mercury electrode surface was identified. A validated simple, rapid, sensitive, specific, precise and inexpensive square-wave voltammetric procedure is described for the determination of ethinylestradiol following its accumulation onto a hanging mercury drop electrode in a Britton–Robinson universal buffer of pH 7. The optimal procedural conditions were: accumulation potential E acc =−0.7V versus Ag/AgCl/KCls, accumulation duration=60s, pulse-amplitude=70mV, scan increment=10mV and frequency=120Hz. Limits of detection (LOD) and quantification (LOQ) of 5.9×10−10 M and 1.9×10−9 M bulk ethinylestradiol, respectively, were achieved. The proposed procedure was successfully applied to the quantification of ethinylestradiol in pharmaceutical formulation (Ethinyl-oestradiol® tablets) and in human serum and plasma without the necessity for sample pretreatments and/or time-consuming extraction or evaporation steps prior to the analysis. LOD of 8.7×10−10 M and 3×10−9 M and LOQ of 2.9×10−9 M and 1×10−8 M of ethinylestradiol were achieved in human serum and plasma, respectively. [Copyright &y& Elsevier]

Abstract: The electrochemical behavior of the antibiotic drug cefazolin sodium (CFZ) in Britton–Robinson buffers (pH 2–11) at the mercury electrode was studied by means of dc-polarography, cyclic voltammetry, controlled-potential coulometry and square-wave adsorptive stripping voltammetry techniques. A validated square-wave adsorptive cathodic stripping voltammetric procedure was described for the trace determination of cefazolin in bulk form up to limits of detection and quantitation of 2.6×10−10 M and 8.6×10−10 M, respectively. The method was successfully applied for determination of cefazolin in pharmaceutical preparation without the necessity for samples pretreatment or any time-consuming extraction or evaporation steps prior to the analysis. [Copyright &y& Elsevier]

The polarographic behavior of amiloride hydrochloride has been studied in Britton–Robinson buffers of pH 1.9–11. In acidic medium at pH≤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 &z.sbnd;CH&z.dbnd6;NH of the imidino amide group with the release of NH3. While the second wave may be due to the saturation of the C&z.dbnd6;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 2.5×10−5 to 2.5×10−4 M amiloride. The limits of detection (LOD) and quantitation (LOQ) of the procedure were 1×10−5 and 3.3×10−4 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: Eacc=−0.9 V, tacc=30 s, scan rate=20 mV, pulse-height=90 mV and Britton–Robinson buffer of pH 8. The calibration graph was obtained over the concentration range 2×10−8 to 1×10−6 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. [Copyright &y& Elsevier]

Chlordiazepoxide is a sedative-hypnotic drug widely employed as a transquilizer and anti-depressant. Its electrochemical behavior in Britton–Robinson (B–R) buffers of pH 2–11 at a mercury electrode has been investigated using dc-polarography, cyclic voltammetry and controlled-potential coulometry. Polarograms of the drug in B–R buffers of pH 2–10 exhibited three 2-electron waves, while at pH>10, only a single 4-electron wave was observed. The first, second, and third waves in buffers of pH≤10 may be attributed to the reduction of N-oxide, C&z.dbnd6;N and C&z.sbnd;N centers, respectively. The single wave (pH>10) may be due to the reduction of both the N-oxide and C&z.dbnd6;N centers in a one step. The shift of the E1/2, values to more negative potentials upon the increase of pH indicated the involvement of protons in the electrode reaction and that the proton-transfer reaction precedes the electrode process proper. The estimated data indicated that, one proton and two electrons are participated in the rate-determining step of each of the reduced centers. The general sequence of chlordiazepoxide reduction processes via each of its reactant centers may be expressed as: H+, e, e, H+(fast).Based on the interfacial adsorptive character of the drug onto the mercury electrode, a validated direct square-wave adsorptive cathodic stripping (SWAdCS) voltammetric procedure has been described for the trace determination of the drug in bulk form, tablets and human serum. The procedure did not require sample pretreatment or time-consuming extraction or evaporation steps prior to the assay of the drug. The optimized operational conditions of the proposed procedure have been found to be: accumulation potential Eacc.=−0.9 V, accumulation time tacc.=30 s, pulse-amplitude=50 mV, scan increment=10 mV and frequency=120 Hz. The proposed procedure is much more simple, fast, sensitive, costly low and achieved much more lower limits of detection (LOD) (4.4×10−10 M and 6.6×10−10 M) and limits of quantitation (LOQ) (1.5×10−9 M and 2.2×10−9 M), respectively in pharmaceutical formulation and spiked human serum, compared to previously reported methods. [Copyright &y& Elsevier]