Derivative spectrophotometry in the visible region using absorbance versus log wavelength or wavenumber determination of cyanocobalamin in injection solutions.
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).
Wahbi
Abdel Aziz
AA
Pharmaceutical Analytical Chemistry Department, Faculty of Pharmacy, University of Alexandria, Alexandria 21521, Egypt. Abdel_azizwahbi@yahoo.com
Hassan
Ekram
E
Barary
Magda
M
Khamis
Essam
E
Hamdi
Dalia
D
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*
D019999:Pharmaceutical Solutions; D014803:Vitamin B Complex; D014805:Vitamin B 12