Salem H.Mohamed D.Pharmaceutical Analytical Chemistry DepartmentFaculty of PharmacyOctober University for Modern Sciences and ArtsOctober City11787 6Egypt; Analytical Chemistry DepartmentFaculty of PharmacyHelwan UniversityEin HelwanCairo11795Egypt; Analytical Chemistry DepartmentFaculty of PharmacyDeraya UniversityCairo14511Egypt2020-01-092020-01-09201513861425https://doi.org/10.1016/j.saa.2014.12.099PubMed ID 25594211https://t.ly/ve8mqScopusSix simple, specific, accurate and precise spectrophotometric methods were developed and validated for the simultaneous determination of the analgesic drug; paracetamol (PARA) and the skeletal muscle relaxant; dantrolene sodium (DANT). Three methods are manipulating ratio spectra namely; ratio difference (RD), ratio subtraction (RS) and mean centering (MC). The other three methods are utilizing the isoabsorptive point either at zero order namely; absorbance ratio (AR) and absorbance subtraction (AS) or at ratio spectrum namely; amplitude modulation (AM). The proposed spectrophotometric procedures do not require any preliminary separation step. The accuracy, precision and linearity ranges of the proposed methods were determined. The selectivity of the developed methods was investigated by analyzing laboratory prepared mixtures of the drugs and their combined dosage form. Standard deviation values are less than 1.5 in the assay of raw materials and capsules. The obtained results were statistically compared with each other and with those of reported spectrophotometric ones. The comparison showed that there is no significant difference between the proposed methods and the reported methods regarding both accuracy and precision. � 2015 Elsevier B.V. All rights reserved.EnglishAbsorbance subtraction methodAmplitude modulation methodDantrelax compound� capsulesDantrolene sodiumParacetamolAmplitude modulationDrug dosageDrug productsModulationMuscleSodiumSpectrophotometersAccuracy and precisionCombined dosage formsComparative studiesParacetamolSimultaneous determinationsSpectro-photometric methodStandard deviationSubtraction methodSpectrophotometryanalgesic agentdantrolenedrug combinationmuscle relaxant agentparacetamolcomparative studydrug combinationevaluation studylimit of detectionproceduresspectrophotometryAcetaminophenAnalgesicsDantroleneDrug CombinationsLimit of DetectionNeuromuscular AgentsSpectrophotometryArticlehttps://doi.org/10.1016/j.saa.2014.12.099PubMed ID 25594211