RESUMEN

An electroanalytical methodology was developed by direct differential pulse voltammetric (DPV) measurement of Levodopa (LD), Carbidopa (CD) and Entacapone (ENT) mixture using bare glassy carbon electrode (GCE) in Britton Robinson (BR) buffer (pH = 2.0). A multivariate calibration model was then applied to the exported preprocessed voltammetric data using partial least square (PLS) as a chemometric tool. Additionally, the model was cross-validated and the number of latent variables (LVs) were determined to produce a reliable model for simultaneous quantitation of the three drugs either in their synthetic mixtures or in their marketed pharmaceutical formulation with high accuracy and precision. Data preprocessing was used to tackle the problem of lacking bi-linearity which is commonly found in electrochemical data. The proposed chemometric model was able to provide fast and reliable technique for quantitative determination of antiparkinson drugs in their dosage forms. This was successfully achieved by utilizing sixteen mixtures as calibration set and nine mixtures as validation set. The percent recoveries for LD, CD and ENT were found to be 100.05% ± 1.28%, 100.04% ± 0.53% and 99.99% ± 1.25%, respectively. The obtained results of the proposed method were statistically compared to those of a previously reported High Performance Liquid Chromatography (HPLC) methodology. Finally, the presented analytical method strongly supports green analytical chemistry regarding the minimization of potentially dangerous chemicals and solvents, as well as reducing energy utilization and waste generation.

RESUMEN

In this work, two chromatographic methods are developed and validated for the determination of enrofloxacin and bromhexine (BRM) HCl in the presence of two of their specified impurities, ciprofloxacin and BRM impurity C. The suggested chromatographic methods included the use of thin layer chromatography (TLC-densitometry) and high-performance liquid chromatography (HPLC). In case of TLC-densitometry, good separation was achieved by using mobile phase of n.butanol:acetone:water:glacial acetic acid:triethylamine (10:3:1:0.5:0.5, by volume) on silica gel stationary phase at 254-nm detection. The developed HPLC method used BDS HYPERSIL C18 column with a mobile phase of water:acetonitrile:methanol:triflouroacetic acid. A linear gradient elution of 75-10%, 20-50% and 5-40% for water, acetonitrile and methanol, respectively, was applied in 13 min at a flow rate of 1.5 mL min-1. These methods were sufficient to separate the four substances simultaneously, and they are validated as per International Conference on Harmonization guidelines.

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RESUMEN

Different innovative spectrophotometric methods were introduced for the first time for simultaneous quantification of sacubitril/valsartan in their binary mixture and in their combined dosage form without prior separation through two manipulation approaches. These approaches were developed and based either on two wavelength selection in zero-order absorption spectra namely; dual wavelength method (DWL) at 226nm and 275nm for valsartan, induced dual wavelength method (IDW) at 226nm and 254nm for sacubitril and advanced absorbance subtraction (AAS) based on their iso-absorptive point at 246nm (λiso) and 261nm (sacubitril shows equal absorbance values at the two selected wavelengths) or on ratio spectra using their normalized spectra namely; ratio difference spectrophotometric method (RD) at 225nm and 264nm for both of them in their ratio spectra, first derivative of ratio spectra (DR1) at 232nm for valsartan and 239nm for sacubitril and mean centering of ratio spectra (MCR) at 260nm for both of them. Both sacubitril and valsartan showed linearity upon application of these methods in the range of 2.5-25.0µg/mL. The developed spectrophotmetric methods were successfully applied to the analysis of their combined tablet dosage form ENTRESTO™. The adopted spectrophotometric methods were also validated according to ICH guidelines. The results obtained from the proposed methods were statistically compared to a reported HPLC method using Student t-test, F-test and a comparative study was also developed with one-way ANOVA, showing no statistical difference in accordance to precision and accuracy.

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