Validated green high‐performance liquid chromatographic methods for the determination of coformulated pharmaceuticals: A comparison with reported conventional methods

The introduction of sustainable development concepts to analytical laboratories has recently gained interest, however, most conventional high‐performance liquid chromatography methods do not consider either the effect of the used chemicals or the amount of produced waste on the environment. The aim of this work was to prove that conventional methods can be replaced by greener ones with the same analytical parameters. The suggested methods were designed so that they neither use nor produce harmful chemicals and produce minimum waste to be used in routine analysis without harming the environment. This was achieved by using green mobile phases and short run times. Four mixtures were chosen as models for this study; clidinium bromide/chlordiazepoxide hydrochloride, phenobarbitone/pipenzolate bromide, mebeverine hydrochloride/sulpiride, and chlorphenoxamine hydrochloride/caffeine/8‐chlorotheophylline either in their bulk powder or in their dosage forms. The methods were validated with respect to linearity, precision, accuracy, system suitability, and robustness. The developed methods were compared to the reported conventional high‐performance liquid chromatography methods regarding their greenness profile. The suggested methods were found to be greener and more time‐ and solvent‐saving than the reported ones; hence they can be used for routine analysis of the studied mixtures without harming the environment.     

Synthesis and in vitro behavior of iron-crosslinked N-methyl and N-benzyl hydroxamated derivatives of alginic acid as controlled release carriers

N-methyl and N-benzyl hydroxylamines were synthetically conjugated to alginic acid to produce hydroxamated derivatives with different degrees of substitution. The new polymeric materials were used to form coordinate complexes with iron(III). The hydroxamated derivatives as well as their iron complexes were characterized using infrared spectroscopy and differential scanning calorimetry.Phenobarbitone-loaded and blank beads were prepared utilizing the new iron-crosslinked hydroxamated polymers and evaluated with respect to their ability to control drug release, as well as their iron leaching properties.The iron-crosslinked polymeric composites proved capable of encapsulating the model drug and sustaining its release in the dissolution media, the release profiles were sensitive to the type and degree of substitution.     

Application of packed column supercritical fluid chromatography to the simultaneous determination of seven anticonvulsant drugs

Studies of speed, resolution, and selectivity have shown that packed column supercritical fluid chromatography (PCSFC) is a viable technique for the isocratic, isothermal and isobaric separation of seven anticonvulsants, viz., phenobarbitone, phenytoin sodium, phethenylate sodium, nitrazepam, clonazepam, carbamazepine, and primidone, and their simultaneous estimation. The drugs were eluted from a JASCO, RP-C₁₈ (250×4.6 mm) 10 μ packed column with a binary mobile phase of carbon dioxide and methanol, using ibuprofen as the internal standard. The effect of pressure, temperature, modifier concentration, and the rate of flow of CO₂ on retention and selectivity of all the analytes were studied and the parameters optimised. Without methanol in the mobile phase none of the solutes eluted. Changing modifier concentration was the most effective physical parameter for changing retention and selectivity. The analytes were detected using a UV detector at 215 nm. An arbitrary mixture of eight components was baseline resolved in 7 min. The study includes a successful attempt at quantification of the drugs. Chromatographic and analytical figures of merit have been listed. The present work holds promise for a possible replacement of HPLC with SFC for the separation and assay of drugs of different families.     

Vibrational spectra and normal coordinate analysis of diazepam, phenytoin and phenobarbitone

Vibrational spectroscopy is an important tool for the structural investigation of the organic molecules. In the present investigation, a normal coordinate analysis has been carried out on some anti-epileptic drugs, viz. diazepam, phenytoin and phenobarbitone. Diazepam is a derivative of benzodiazepine, phenytoin is a derivative of hydanation and pheonobarbitone is a barbiturate. The infrared spectra of the compounds are recorded in the region 4000-400 cm(-1) and Raman spectra are recorded in the region 3500-50 cm(-1). From the structural point of view, diazepam, phenytoin and phenobarbitone have been assumed to C(s) point group. A systematic set of symmetry coordinates has been constructed for these compounds and Wilson's FG matrix method has been applied for the normal coordinate analysis using general quadratic valance force field. The potential energy distribution is also calculated to check the vibrational band assignments.