Lotfy H.M.Mohamed D.Mowaka S.Analytical Chemistry DepartmentFaculty of PharmacyCairo UniversityKasr-El Aini StreetCairo11562Egypt; Pharmaceutical Chemistry DepartmentFaculty of Pharmaceutical Sciences and Pharmaceutical IndustriesFuture UniversityCairo12311Egypt; Analytical Chemistry DepartmentFaculty of PharmacyHelwan UniversityEin HelwanCairo11795Egypt; Pharmaceutical Analytical Chemistry DepartmentFaculty of PharmacyOctober University for Modern Sciences and ArtsOctober City117876Egypt; Department of Analytical ChemistryFaculty of PharmacyBritish University in EgyptEl-Sherouk City11837Egypt2020-01-092020-01-09201513861425https://doi.org/10.1016/j.saa.2015.04.076PubMed ID 25978011https://t.ly/3GXOwScopusSimple, specific, accurate and precise spectrophotometric methods were developed and validated for the simultaneous determination of the oral antidiabetic drugs; sitagliptin phosphate (STG) and metformin hydrochloride (MET) in combined pharmaceutical formulations. Three methods were manipulating ratio spectra namely; ratio difference (RD), ratio subtraction (RS) and a novel approach of induced amplitude modulation (IAM) methods. The first two methods were used for determination of STG, while MET was directly determined by measuring its absorbance at ?<inf>max</inf> 232 nm. However, (IAM) was used for the simultaneous determination of both drugs. Moreover, another three methods were developed based on derivative spectroscopy followed by mathematical manipulation steps namely; amplitude factor (P-factor), amplitude subtraction (AS) and modified amplitude subtraction (MAS). In addition, in this work the novel sample enrichment technique named spectrum addition was adopted. The proposed spectrophotometric methods did 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 pharmaceutical formulations. Standard deviation values were less than 1.5 in the assay of raw materials and tablets. The obtained results were statistically compared to that of a reported spectrophotometric method. The statistical comparison showed that there was no significant difference between the proposed methods and the reported one regarding both accuracy and precision. � 2015 Elsevier B.V. All rights reserved.Englishجامعة أكتوبر للعلوم الحديثة والآدابMSA UniversityUniversity for Modern Sciences and ArtsOctober University for Modern Sciences and ArtsAmplitude subtraction methodInduced amplitude modulation methodMetformin hydrochlorideModified amplitude subtraction methodSitagliptin phosphateAmplitude modulationBinary mixturesMixturesModulationSpectrophotometersSpectrophotometryInduced amplitude modulation methodMetformin hydrochloridesPharmaceutical formulationSimultaneous determinationsSitagliptinSpectro-photometric methodStatistical comparisonsSubtraction methodDrug productsantidiabetic agentdrug combinationmetforminsitagliptintabletcomparative studydrug combinationlimit of detectionproceduresspectrophotometrytabletvalidation studyDrug CombinationsHypoglycemic AgentsLimit of DetectionMetforminSitagliptin PhosphateSpectrophotometryTabletsArticlehttps://doi.org/10.1016/j.saa.2015.04.076PubMed ID 25978011