Simultaneous determination of a quaternary mixture of oxomemazine, sodium benzoate, guaifenesin and paracetamol by chromatographic methods

Method development for simultaneous determination of active ingredients in cough and cold pharmaceuticals by high performance liquid chromatography

A rapid, simple and efficient liquid chromatographic method was developed for simultaneous determination of three active ingredients namely, chlorpheniramine maleate, phenylephrine hydrochloride and guaifenesin along with sodium benzoate preservative common cold medications (syrups) and the method was validated based on the International Conference on Harmonization (ICH) and United State Pharmacopeia (USP) guidelines. Separation of the analytes was achieved within 15 min on a nucleosil gravity phenyl column in a single run with a mobile phase consisting of methanol: buffer mixture (15:85 v/v) at room temperature, in isocratic mode with flow rate of 0.8 mL min-1. A comprehensive study on specificity, range, accuracy (recovery), intraday and interday precisions, limit of detection, limit of quantitation, robustness, ruggedness, system suitability and specification was performed as a part of method validation. The linearity was obtained in the range of 7.1-12.2 μg mL-1 (r2 = 0.9984), 17.6-30.1 μg mL-1 (r2 = 0.9995), 39.6-67.8 μg mL-1 (r2 = 0.9995) and 351.1-601.8 μg mL-1 (r2 = 0.9996) for chlorpheniramine maleate, phenylephrine hydrochloride, sodium benzoate and guaifenesin, respectively. The proposed liquid chromatographic method was successfully applied for the routine analysis of these compounds in different commercial cough and cold pharmaceutical preparations including syrups with no interference from the excipients.

Selective Determination of Levodopa in the Presence of Vitamin B6, Theophylline and Guaifenesin Using a Glassy Carbon Electrode Modified with a Composite of Hematoxylin and Graphene/ZnO

An electrode has been developed based on using a composite of hematoxylin/graphene/ZnO nanocomposite to modify a glassy carbon electrode (GCE). The electrode (HGGCE) was tested and found to be applicable for the voltammetric analysis of levodopa in the presence of vitamin B₆, theophylline and guaifenesin using a 0.1 M phosphate buffer solution (PBS) pH 7 as the solvent. The HGGCE was used as the working electrode in cyclic voltammetry (CV) and square wave voltammetry (SWV) studies on the electrochemical behavior of levodopa at its surface. The results showed a dramatic enhancement in the oxidation current of levodopa and a shift in its oxidation potential towards more negative potentials as opposed to identical tests using bare GCE as the working electrode. The studies showed that the increase in the oxidation current has two linear profiles in two concentration ranges of 0.05 - 90.0 and 90.0 - 1000.0 μM. The detection limit of SWV analysis using the modified electrode was determined to be 0.03 μM (S/N = 3). Further advantages of the methods based on HGGCE include the simple modification procedure of the electrode, as well as its excellent sensitivity and reproducibility. The modified electrode was eventually found to be applicable to the determination of mixtures of levodopa, vitamin B₆, theophylline and guaifenesin in real samples.