An optimization approach based on full factorial design was employed for developing an HPLC–UV method for simultaneous determination of a quaternary mixture used for the treatment of symptoms related to common cold and COVID-19. The quaternary mixture is composed of paracetamol, levocetirizine dihydrochloride, phenylephrine hydrochloride and ambroxol hydrochloride. The developed technique is a green, fast and simple method that uses isocratic elution of mobile phase consisting of 20:5:75 (v/v) of ethanol: acetonitrile: 2.5 mM heptane-1-sulphonic acid sodium salt at pH 6.5 $$\pm$$ ± 0.02. The chromatographic separation was carried out using Hypersil BDS Cyano LC Column (250 × 4.6 mm, 5 μm) with 230 nm UV detection and 1.0 mL/min. flow rate. Avoiding the routine methodology and resorting to the modern technology—represented in the usage of experimental design—allows rapid determination of the four drugs using the optimum quantity of chemicals to avoid any waste of resources. The quaternary mixture was eluted in less than 9 min., where retention times of paracetamol, levocetirizine dihydrochloride, phenylephrine hydrochloride and ambroxol hydrochloride were found to be 2.2, 3.8, 6.6 and 8.8 min., respectively. The calibration graphs of the four drugs were linear over concentration ranges of 50.0–500.0, 0.5–20.0, 0.5–20.0 and 0.5–100.0 µg/mL for paracetamol, levocetirizine dihydrochloride, phenylephrine hydrochloride and ambroxol hydrochloride, respectively with correlation coefficients higher than 0.999. The method is accurate with mean recoveries between 99.87 and 100.04%, precise, as %RSD for the intraday and interday precision were between 0.61 and 1.64% and very sensitive with limit of detections (LOD)’s between 29 and 147 ng/mL and limit of quantification (LOQ)’s between 95 and 485 ng/mL. The proposed method was successfully applied for the analysis of the four drugs either in raw materials or in prepared tablet with the least amount of chemicals within short time. It is also validated following International Conference on Harmonization Guidelines. The proposed method was found to be green according to the most common greenness assessment tools; NEMI, GAPI, Analytical Eco-Scale and AGREE methods. The advantages of the proposed method qualify it for routine analysis of the studied drugs either in single or co-formulated dosage form in quality control labs.

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A simple, sensitive, and economic quantitation of two co-formulated antihypertensive drugs, valsartan and amlodipine besylate was carried out in less than 4 minutes.

A green, quick and sensitive spectrofluorimetric technique was investigated and validated for the assay of three different drugs namely, ketoprofen (KPN), paracetamol (PAR), and chlorzoxazone (CLX).

The native fluorescence of sotalol hydrochloride (SOT) was used as a basis for establishing a new method of analysis for SOT in tablets and spiked human plasma. The fluorescence of SOT in water was measured at 310 nm when excited at 235 nm. The detection limit (LOD) was 0.37 ng/mL and the quantification limit (LOQ) was 1.08 ng/mL. The proposed method offers high sensitivity which permits determination of SOT, even if present in a very small amount, in human plasma. The obtained results were successfully compared to that of a reference pharmacopeial method and statistical analysis proved a good agreement between the results of both methods. Further investigation of the SOT stability upon exposure to various stress conditions, such as acidic, alkaline, oxidative and photolytic degradation conditions was also performed. The kinetics of acidic, alkaline and oxidative degradation of the drug showed a pseudo first order degradation reaction. A proposal of the degradation pathway was suggested and confirmed by developing a thin layer chromatographic method used for separation of SOT and its acidic and alkaline degradation products.