The simultaneous measurement of quaternary mixture in over-the-counter cold medications using sequential spectrophotometric resolution approach enhanced with in-lab sample enrichment

Advanced chemometric methods for simultaneous quantitation of caffeine, codeine, paracetamol, and p-aminophenol in their quaternary mixture

Two different multivariate techniques have been applied for the quantitative analysis of caffeine, codeine, paracetamol and p-aminophenol (PAP) in quaternary mixture, namely, Partial Least Squares (PLS-1) and Artificial Neural Networks (ANN). For suitable analysis, a calibration set of 25 mixtures with various ratios of the drugs and PAP impurity were established using a 4-factor 5-level experimental design. The most meaningful wavelengths for the chemometric models were chosen using Genetic Algorithm (GA) as a variable selection technique. By using an independent validation set, the validity of the proposed methods was evaluated. A comparative study was established between the three multivariate models (PLS-1, GA-PLS and GA-ANN). The comparison between the various models revealed that the GA-ANN model was superior at resolving the highly overlapped spectra of this quaternary combination. The drugs were successfully quantified in their pharmaceutical dosage form utilizing the GA-ANN models.

Continuous wavelet transform for solving the problem of minor components in quantitation of pharmaceuticals: a case study on the mixture of ibuprofen and phenylephrine with its degradation products

The presence of minor components represents a challenging problem in spectrophotometric analysis of pharmaceuticals. If one component has a low absorptivity or present in a low concentration compared to the other components, this will hinder its quantitation by spectrophotometric methods. Continuous Wavelet Transform (CWT) as a signal processing technique was utilized to figure out a solution to such a problem. A comparative study was established between traditional derivative spectrophotometry (Numerical Differentiation, ND) and CWT to indicate the advantages and limitations of each technique and possibility of solving the problem of minor components. A mixture of ibuprofen (IBU) and phenylephrine (PHE) with its degradation products forming a ternary mixture was used for comparing the two techniques. The two techniques were applied on raw spectral data and on ratio spectra data resulting in four methods, namely ND, CWT, Derivative Ratio-Zero Crossing (DRZC) and Continuous Wavelet Transform Ratio-Zero Crossing (CWTR-ZC) methods. By comparing the results in laboratory prepared mixtures, CWT technique showed advantages in analysis of mixtures with minor components than ND. The proposed methods were validated according to the ICH guideline Q2(R1), where their linearity was established with correlation coefficient ranging from 0.9995 to 0.9999. The linearity was in the range 3-40 μg/mL for PHE in all methods, while for IBU it was 20-180 and 30-180 μg/mL in CWT and ND methods, respectively. The CWT methods were applied for quantitative determination of the drugs in their dosage form showing the ability of the methods to quantitate minor components in pharmaceutical formulations.

Chromatographic reversed HPLC and TLC-densitometry methods for simultaneous determination of serdexmethylphenidate and dexmethylphenidate in presence of their degradation products-with computational assessment

Two Chromatographic methods have been established and optimized for simultaneous determination of serdexmethylphenidate (SER.DMP) and dexmethylphenidate (DMP) in the presence of their degradation products. The first method is a reversed phase high performance liquid chromatography with diode array detection (HPLC-DAD). Isocratic separation was carried out on Waters X-bridge Shield RP₁₈ column (150×3.9×5 μm particle size) using a mixture of 5 mM phosphate buffer (pH 5.5): acetonitrile (40:60, v/v) as a mobile phase, flow rate 1 mL/min and detection at 220 nm. The second method is a thin-layer chromatography (TLC)-densitometry method using methanol: chloroform (70:30, v/v) as a mobile phase and UV scanning at 220 nm. In HPLC method, the linearity range of SER.DMP was (2.5-25 μg/mL); with LOD (0.051 μg/mL) and LOQ (0.165 μg/mL) while for DMP was (2.5-25 μg/mL); with LOD and LOQ of (0.098 μg/mL) and (0.186 μg/mL), respectively. For TLC method the sensitivity range of SER.DMP was (5-25 μg/mL), LOD was (0.184 μg/spot), while LOQ was (0.202 μg/ spot) whereas for DMP the sensitivity range was (5-25 μg/mL) with LOD of (0.115 μg/ spot) and LOQ of (0.237 μg/ spot), respectively. SER.DMP was found to be equally labile to acidic and alkaline hydrolysis, whereas DMP was sensitive to acidic hydrolysis only. Both drugs were successfully determined in presence of acidic and basic degradants by the two developed methods (stability indicating assay method). Chromatographic separation of the degradation products was carried out on TLC aluminum silica plates 60 F254, as a stationary phase, using methanol: dichloroethane: acetonitrile (60:20:20 v/v), as a mobile phase. The degradation pathway was confirmed using TLC, IR, ¹H-NMR and mass spectroscopy; moreover, the separation power was correlated to the computational results by applying molecular dynamic simulation. The developed methods were validated according to the International Conference on Harmonization (ICH) guidelines demonstrating good accuracy and precision. They were successfully applied for quantitation of SER.DMP and DMP in pure and capsule forms. The results were statistically compared with those obtained by the reported method in terms of accuracy, precision and robustness, and no significant difference was found.