Validation of Intersection Absorption Spectrum for Simultaneous Determination of Betamethasone Valerate and Neomycin Sulfate in Cream

Betamethasone valerate and neomycin sulfate are combinations of anti-infection in skin cream. The purpose of this study was to validate intersection absorption spectrum methods and simultaneous determination of betamethasone valerate and neomycin sulfate in the skin cream using 70% ethanol as solvent. The simultaneous determination of a sample was performed with the intersection point spectrophotometric methods when betamethasone valerate and neomycin sulfate absorption spectrum were overlapped and the intersection points were obtained at wavelength 245.4 nm. Each level of betamethasone valerate and neomycin sulfate were calculated using the regression equation. The simultaneous determination of betamethasone valerate and neomycin sulfate in cream supply obtained levels of (107,98 1.6491)% betamethasone valerate and (94.81 2.6958)% neomycin sulfate. The validation test for betamethasone valerate were as follows accuracy was 99.90%, precision was 1.09%, LOD was 0.645 g/mL, and LOQ was 2.15 g/mL whereas neomycin sulfate was as follows accuracy was 99.67%, precision was 1.46%, LOD was 2.215 g/mL, and LOQ was 7.385 g/mL. The mixture of betamethasone valerate and neomycin sulfate used a wavelength of 245.4 nm as the point of intersection of the absorption spectrum and the results met Indonesian pharmacopeia requirements and this method satisfied the validation requirements.