title: Derivative spectrophotometry in the visible region using absorbance versus log wavelength or wavenumber determination of cyanocobalamin in injection solutions.
abstract: Two approaches have been adopted to increase the steepness of the slopes and the sharpness of the curvature of an absorption curve in the visible region. These are recording (i) A (1cm) versus log wavelength or (ii) A (1cm) versus wavenumber. The computer program was tested by calculating the ratios of the first derivative optima for a Gaussian band, and proved that changing wavelength into log wavelength or wavenumber is effective to squeeze an absorption curve non-linearly. Spectrophotometric identification of cyanocobalamin in the visible region was carried out using the ratios (Delta D1/D2) calculated for lambda, log lambda and nu scales. The ratios were highly reproducible and independent of concentration. First, second and fourth-order derivative determination of cyanocobalamin in injection solutions was performed in the visible region at 20040.08, 17452.01, (20040.08 - 17452.01) cm(-1) for D11(nu), D12(nu) Delta D1 (D11-D12) (nu), respectively, and at 18018.02 cm(-1) for D2(nu) and D4(nu).
authors.affiliation: Pharmaceutical Analytical Chemistry Department, Faculty of Pharmacy, University of Alexandria, Alexandria 21521, Egypt. Abdel_azizwahbi@yahoo.com
authors.forename: Abdel Aziz
authors.initials: AA
authors.lastname: Wahbi
authors.forename: Ekram
authors.initials: E
authors.lastname: Hassan
authors.forename: Magda
authors.initials: M
authors.lastname: Barary
authors.forename: Essam
authors.initials: E
authors.lastname: Khamis
authors.forename: Dalia
authors.initials: D
authors.lastname: Hamdi
mesh_terms: D007267:Injections; D019999:Pharmaceutical Solutions / Q000737:chemistry*; D015203:Reproducibility of Results; D012984:Software; D013053:Spectrophotometry / Q000379:methods*; D014805:Vitamin B 12 / Q000032:analysis*; D014803:Vitamin B Complex / Q000032:analysis*
chemical_list: D019999:Pharmaceutical Solutions; D014803:Vitamin B Complex; D014805:Vitamin B 12