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Zidvovudine (AZT) is a nucleoside analogue reverse transcriptase inhibitor (NRTI), a class of anti-retroviral drug. A stability-indicating assay method for AZT was developed in line with ICH guideline. Successful separation of AZT and its degradation products was achieved by gradient elution mode on reverse phase C18 column using 10 mM ammonium acetate: acetonitrile as the mobile phase at 0.8 mL/min flow rate, 25 µL injection volume, 30 °C column temperature and 285 nm detection wavelength. Two major acid degradation products were identified and characterized by liquid chromatography–electrospray ionization mass spectrometry (LC–ESI/MS/MS) and accurate mass measurements. The probable mechanisms for the formation of degradation products were identified based on a comparison of the fragmentation pattern of the [M + H] + ions of AZT and its degradation products. One of the degradation products, DP-1, was isolated by semi-preparative high performance liquid chromatography (HPLC) using Waters XBridge Prep C18 (250 mm×10 mm, 5 µm). Degradation products showed higher toxicity compared to the drug in some models assessed by TOPKAT software. The method validation was performed with respect to robustness, specificity, linearity, precision and accuracy as per ICH guideline Q2 (R1).

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An efficient method for the computation of current density and surface concentration distributions in electrochemical processes is analyzed using the commercial mathematical software FEMLAB. To illustrate the utility of the software, the procedure is applied to some realistic problems encountered in electrochemical engineering, such as current distribution in a continuous moving electrode, parallel plate electrode, hull cell, curvilinear hull cell, thin layer galvanic cell, through-hole plating, and a recessed disc electrode. The model equations of the above cases are considered and their implementations into the software, FEM-LAB, are analyzed. The technique is attractive because it involves a systematic way of coupling equations to perform case studies.

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