Hydro-organic mobile phase and factorial design application to attain green HPLC method for simultaneous assay of paracetamol and dantrolene sodium in combined capsules.

The greenness of any analytical method has become a very important aspect of a good analytical method. However, most chromatographic methods depend on the usage of relatively large amounts of lethal and un-decaying chemicals and solvents. So, a green approach based on the full factorial design was employed to develop a simple and rapid HPLC technique for concurrent determination of paracetamol and dantrolene sodium in their combined capsules. Both drugs are highly recommended to be administered together in patients with severe musculoskeletal disorders. Avoiding the routine methodology and resorting to the modern technology represented in the usage of experimental design allows rapid determination of the studied drugs using the optimum quantity of chemicals to avoid any waste of resources. Simultaneous separation of a binary mixture of paracetamol and dantrolene sodium was accomplished using a reversed phase Hypersil C18 column using an eco-friendly isocratic eluent. The used mobile phase consisted simply of ethanol: water (40:60, v/v). Orthophosphoric acid was used to adjust the pH of the mobile phase to 4.5. Triethanolamine (0.2%) was added aiming to reduce the peak tailing. The assay was completed within less than 6 min adopting 0.8 mL/min as a flow rate. The detection was carried out using a UV-detector at 290 nm. The suggested technique shows a linear correlation over concentration ranges of 1.0-200 and 1.0-40 µg/mL for paracetamol and dantrolene sodium, respectively. The suggested technique allowed the simultaneous analysis of the two co-formulated drugs in their synthetic mixture and combined capsule. The suggested technique is considered a greener substitute for the other reported HPLC techniques through the usage of safer solvents and chemicals, along with decreasing both waste output and analysis time. The method is accurate with recoveries between 97.85 and 101.27%, precise, as %RSD for the intraday and interday precision were between 0.39 and 1.72% and very sensitive with limits of detection (LOD)'s 0.15 and 0.18 µg/ml and limits of quantification (LOQ)'s 0.48 and 0.61 µg/ml for paracetamol and dantrolene sodium, respectively. The method greenness was ensured through its assessment by four greenness metrics. It is also validated following the International Conference on Harmonization Guidelines. The recommended technique could be a good alternative to traditional methods in the routine quality control analysis of the studied drugs due to its minimum harm to the planet or human beings.