An RP-HPLC method with a UV detector was developed for the simultaneous quantification of diclofenac diethylamine, methyl salicylate, and capsaicin in a pharmaceutical formulation and rabbit skin samples. The separation was achieved using a Thermo Scientific ACCLAIM^TM 120 C₁₈ column (Waltham, MA, USA, 4.6 mm × 150 mm, 5 µm). The optimized elution phase consisted of deionized water adjusted to pH = 3 using phosphoric acid mixed with acetonitrile in a 35:65% (v/v) ratio with isocratic elution. The flow rate was set at 0.7 mL/min, and the detection was performed at 205 nm and 25 °C. The method exhibits good linearity for capsaicin (0.05–70.0 µg/mL), methyl salicylate (0.05–100.0 µg/mL), and diclofenac diethylamine (0.05–100.0 µg/mL), with low LOD values (0.0249, 0.0271, and 0.0038 for capsaicin, methyl salicylate, and diclofenac diethylamine, respectively). The RSD% values were below 3.0%, indicating good precision. The overall greenness score of the method was 0.61, reflecting its environmentally friendly nature. The developed RP-HPLC method was successfully applied to analyze Omni Hot Gel^® pharmaceutical formulation and rabbit skin permeation samples.

Clopidogrel is an oral, thienopyridine class antiplatelet agent used to inhibit blood clots in coronary arteries, peripheral vascular and cerebrovascular diseases. A spectrophotometric method was developed for clopidogrel bisulfate (CLOP·H₂SO₄) determination using bromocresol green (BCG) as an ion-pairing agent. To explore the binding nature of CLOP·H₂SO₄ with BCG at a molecular level, quantum chemical calculations have been performed. DFT based full geometry optimization has been carried out for BCG and clopidogrel in basic (CLOP) and protonated (CLOP⁺) forms as well as for BCG ion-pairs with CLOP and CLOP·H₂SO₄. The DFT calculations referred to the stability of the BCG–CLOP⁺ ion-pair and its spontaneous formation reaction from BCG and CLOP·H₂SO₄ compared to the BCG–CLOP-ion-pair. Furthermore, the UV-visible spectra and their corresponding excited states and electronic transitions for BCG, BCG–CLOP⁺ ion-pair, and BCG–CLOP ion-pair have been investigated. These spectra provided a molecular level understanding of the nature of the different intra-molecular and intermolecular electronic transitions in the BCG ion-pairs with CLOP⁺. Moreover, the quantitative analysis based on extracting a yellow-formed ion-pair into chloroform from aqueous medium was carried out. The ion-pair exhibits an absorption maximum at 413 nm. The optimum conditions of the reactions were studied experimentally and optimized. The calibration graph shows that CLOP·H₂SO₄ can be determined up to 100.0 μg mL⁻¹ with detection limit (LOD) of 0.57 μg mL⁻¹ and quantification limit (LOQ) of 1.86 μg mL⁻¹. The low relative standard deviation values, 0.16–1.16, indicate good precision. The results were compared to other published data and were treated statistically using F and t-tests.

The FDA-approved antiviral drug molnupiravir (MPV) was investigated using a green spectrophotometric approach. With the help of mass spectrometry, UV-visible spectroscopy, and Infrared Fourier transform spectroscopy, this drug was characterized and elucidated structurally. This approach depends on measuring the absorbance in doubly distilled water as a solvent at 240 and 285 nm. Variable parameters were estimated and optimized. Beer's law is up to 35.0 µg/mL under optimal conditions with a correlation coefficient (r2)>0.99. Based on this evaluation, the new method was found to be highly sensitive with a LOD and LOQ of 0.34-0.78 and 1.13-2.59 µg/mL, respectively. Analyses provided reproducible results with a 2.0% relative standard deviation (RSD). As a result of the application of the proposed method, MPV levels were successfully achieved in raw materials, pharmaceutical formulations, and biological fluids. The geometry and energy quantum mechanical calculations were also performed using Becke's three-parameter exchange functional method. Using water as a solvent, Lee-Yang-Parr correlation functional analysis (B3LYP/DFT) confirmed the measured results.

This study focuses on the analysis of hepatitis C drugs, specifically sofosbuvir (SOF) and daclatasvir (DCL), and their oxidative products. The drugs were isolated and characterized using FTIR, 1HNMR, and Mass Spectrometry techniques. Additionally, the drugs were oxidized using cerium (IV) in the presence of sulfuric acid at 100ºC. A spectrophotometric method was developed for the quantitative analysis of SOF and DCL in pure and pharmaceutical forms. The oxidation of the drugs was monitored by back determination of residual Ce(IV) using Fe(II) with ferroin as an indicator at 510 nm. The method demonstrated good sensitivity with RSD%<1.0, and the data were statistically analyzed using t- and F-tests.