Analysis and simulation of the spectra of several brands of aspirin using Raman spectroscopy

Raman spectroscopy is the measurement of the wavelength and intensity of inelastically scattered light from molecules. The Raman scattered light occurs at wavelengths that are shifted from the incident light by the energies of molecular vibrations. The preliminary objective of this research is to define brand names and also to analyse and compare Raman spectral peaks of eight different aspirins from their respective Raman spectra. A software programme called 'PeakFit' was used to analyse one of the spectra and calculate signal to noise ratios for some peaks which are affected by background noise. Raman spectra of eight different aspirins, in solid phase with two of them also conducted in aqueous solution, have been simulated. The Raman spectra of aspirins were measured at room temperature by a specially designed compact system including holographic band pass and notch filters, best from lenses to reduce aberrations, a TE -10 °C cooled CCD and 12,5 cm spectrograph. The spectra were simulated by Gaussian vibrational bands, weighted by Planck distribution function and polynomial and fluorescence background. The contribution of the polarizability changes to the Raman intensity and the degeneracy of the band were taken into account to calculate the molecular parameter of the aromatic ring,n.