ABSTRACT
FT-IR and Raman techniques were employed for the vibrational characterization of the food additive Carmoisine (E122). The equilibrium geometry, various bonding features, and harmonic vibrational wavenumbers have been investigated with the help of density functional theory (DFT) calculations. A good correlation was found between the computed and experimental wavenumbers. Azo stretching wavenumbers have been lowered due to conjugation and pi-electron delocalization. Predicted electronic absorption spectra from TD-DFT calculation have been analysed comparing with the UV-vis spectrum. The first hyperpolarizability of the molecule is calculated. Intramolecular charge transfer (ICT) responsible for the optical nonlinearity of the dye molecule has been discussed theoretically and experimentally. Stability of the molecule arising from hyperconjugative interactions, charge delocalization and C-H ...O, improper, blue shifted hydrogen bonds have been analysed using natural bond orbital (NBO) analysis.
Subject(s)
Food Additives/analysis , Naphthalenesulfonates/analysis , Spectrum Analysis/methods , Absorption , Drug Stability , Food Additives/chemistry , Hydrogen Bonding , Molecular Structure , Naphthalenesulfonates/chemistry , Spectrophotometry, Infrared , Spectrophotometry, Ultraviolet , Spectroscopy, Fourier Transform Infrared/methods , Spectrum Analysis, Raman/methods , VibrationABSTRACT
Fourier transform infrared (FTIR) spectrum of a well-known food dye sunset yellow FCF (E110) has been recorded and analysed. Assignments of the vibrational spectrum has been facilitated by density functional theory (DFT) calculations. The results of the optimized molecular structure obtained on the basis of B3LYP with 6-31G(d) along with the 'LANL2DZ' basis sets give clear evidence for the intramolecular charge transfer (ICT) and strong hydrogen bonding enhancing the optical nonlinearity of the molecule. The first hyperpolarizability of the acidic monoazo dye 'E110' is computed. Azo stretching frequencies have been lowered due to conjugation and pi-electron delocalization. Hydroxyl vibrations with intramolecular H-bonding are analyzed, supported by the computed results. The natural bond orbitals (NBO) analysis confirms this strong hydrogen bond between the hydrogen of the hydroxyl group and nitrogen of the azo group of the molecule. Assignments of benzene and naphthalene ring vibrations are found to agree well with the theoretical wave numbers.
Subject(s)
Azo Compounds/chemistry , Models, Chemical , Quantum Theory , Benzene , Hydrogen Bonding , Molecular Conformation , Naphthalenes/chemistry , Spectroscopy, Fourier Transform Infrared , VibrationABSTRACT
A new, simple and sensitive spectrofluorimetric method was developed for the routine estimation of etoposide, an anticancer drug, in bulk and in pharmaceutical formulations. The medium selected for the estimation of etoposide was methanol : phosphate buffer (pH 7.4) in a ratio of 70 : 30 v/v. Excitation and emission wavelengths used were 240 and 324 nm respectively. The method was validated according to ICH and U.S.P guidelines. Linearity range was 200-1000 ng/ml with detection and quantitation limits of 23 ng/ml and 72 ng/ml respectively. Regression equation obtained was Fluorescence Intensity = 6.704 (Concentration in ng/ml) + 115.4. The drug was found to be stable and there was no interference from the excipients present in different formulations of etoposide.
