Marwa S. Elazazy

Determination of midodrine hydrochloride via Hantzsch condensation reaction: a factorial design based spectrophotometric approach

Correction for ‘Determination of midodrine hydrochloride via Hantzsch condensation reaction: a factorial design based spectrophotometric approach’ by Marwa S. Elazazy et al., RSC Adv., 2015, 5, 48474–48483.

Multivariate analysis of tioconazole — TCNQ charge transfer interaction: Kinetics, thermodynamics and twofold response optimization

Charge-transfer complex (CTC) formation between tioconazole (TCZ) as an n-electron donor and 7, 7, 8, 8-tetracyanoquinodimethane (TCNQ) as a π-acceptor was studied spectrophotometrically with an accompanying kinetic and thermodynamic investigation. Multivariate data analysis via a set of experimental designs was executed for this purpose. A 23 - two-level full factorial design (FFD) was used for inspecting the proposed variables while a face-centered central composite design (FCCCD) was used to adjust the levels of variables proved to be significant. Two responses were quantified as a result of this interaction; complex I (Y1, measured at 743 nm) and complex II (Y2, measured at 842 nm). Derringers function and overlaid contour plots were used to concurrently optimize both responses. Benesi-Hildebrand equation was applied to determine of formation constant (K), and the molar absorptivity (Ɛ) of the formed complex. Different thermodynamic parameters; the standard Gibbs free energy change (∆G°), the standard enthalpy of formation (∆H°) and the standard entropy change (∆S°) were determined for the reaction product. The proposed method was validated regarding the linearity, intra-, and inter-day precision and accuracy, limit of detection, limit of quantification and following the ICH standards. The proposed method was also applied for the determination of TCZ in its pharmaceutical preparations. Having a higher molar absorptivity and higher formation constant, complex II was of choice for all subsequent measurements. Application of Benesi-Hildebrand equation supported the formation of 1: 1 CTC. Thermodynamic study revealed the endothermic characters and the spontaneity of formation of the CTC at high temperature.

Application of Cobalt (II)-EDTA Complex as a Reductant for Molybdophosphoric Acid Used for the Spectrophotometric Assay of Aciclovir, Fluconazole, Ramipril and Secnidazole

A new spectrophotometric method has been described for the assay of aciclovir, fluconazole, ramipril and secnidazole based on formation of insoluble molecular complexes with molybdophosphoric acid (MPA) under acidic conditions. As a second step, a colour reaction has been combined to determine MI’A, released from the complex (and the studied drugs in turn), using a chromogenic reductant; cobalt (Ⅱ)-EDTA complex to produce molybdenum blue Mo(subscript 5+). The colour of the produced Mo(subscript 5+) is measured at 700-710 nm. Appropriate conditions were established for the precipitation and the colour reactions to obtain maximum sensitivity. Under the proposed conditions, this method is applicable over concentration range of 40-580μg ML^(-1). The results demonstrated that the proposed method is equally accurate, precise and reproducible as the official or reported methods thus it is recommended for quality control and routine analysis where time, cost effectiveness and high specificity of analytical techniques are of great importance.