Liquid chromatographic method development and validation for the simultaneous determination of phenylephrine hydrochloride, paracetamol, caffeine and diphenhydramine hydrochloride in pure and formulations

The objective of the proposed work was to develop and validate a simple and sensitive RP-HPLC method for the simultaneous determination of four drugs viz., Phenylephrine hydrochloride (PNY), Acetaminophen (ACN) or Paracetamol (PAR), Caffeine (CFN) and Diphenhydramine Hydrochloride (DPH) in cough syrup combination. The Flourishing separation of four analytes were found by using a high performance liquid chromatography (HPLC) Shimadzu LC 2010 CHT and mobile phase consisting of methanol: buffer (0.1% v/v triethylamine pH-3.0 - adjusted with 0.1N Orthophosphoric acid) in the ratio of 45:55, waters sunfire C18 column (250mm, 4.6 mm and 5μ particle size). An isocratic elution with a flow rate was fixed at 1.0mLmin^-1 and ambient temperature. Detection was carried out with wavelength at 220nm. The retention times of all analytes were stable at 2.2, 3.6, 4.5 and 6.42 minutes for PNY, ACN, CFN and DPH respectively. For these four drugs, the lower limit of detection (LOD) was 1.0, 0.5, 1.5 and 2.5μgmL^-1 and the lower limit of quantification (LOQ) was 3.3, 1.7, 5.0 and 8.3μgmL^-1, respectively. The calibration curves for PNY, ACN, CFN and DPH were found linear over the concentrations of 2.0-7.0, 1.5-7.5, 3.0-9.0 and 6.0-16.0μgmL^-1 respectively. The inter- and intra-day of Relative Standard Deviation (RSD) were less than 2.0%. The developed method is hasty and stable for a combination of drugs, PNY, ACN/PAR, CFN and DPH. The proposed method was applicable for routine analysis of PNY, ACN, CFN and DPH quantification of these selected drugs for their assay in pure and wet cough syrup formulation.