The Raman Shift Wavenumber Measure and the Possibilities of its Application for Quantitative Analysis

Raman spectroscopy is mainly used for qualitative analysis, since the intensity of Raman lines is instrument dependent. At the same time, the high selectivity of Raman spectra stimulates interest in finding ways to use them for quantitative analysis as well, and the development of methods to effectively apply Raman spectroscopy for quantitative analysis is quite relevant. The aim of the study was to investigate the possibilities of using the measure developed at the All-Russian Scientific Research Institute for Optical and Physical Measurements and designed for calibration of Raman instruments on the Raman shift wavenumber scale for quantitative analysis from Raman spectra. The developed measure (registration number in the Federal Information Fund for Ensuring Uniformity of Measurements 93847-24) is a polymer film made of polystyrene with sulfur addition and allows storing and transmitting a unit of Raman shift wavenumber for Raman scattering excitation wavelengths of 532, 633 and 785 nm. The possibility of using this measure for quantitative analysis of substances by measuring the intensity of Raman lines in instrument-independent units is considered. It was found that the use of the measure allows to determine the volume fraction of individual substances (ethanol) with relative random error less than 3 % and relative systematic error less than 6 %. To analyze multicomponent mixtures (alcohols, sugars) with the help of the measure, a multivariate calibration was constructed using the Partial Least Squares method. In this case, the volume fraction of components in an unknown sample was determined with a relative error not exceeding 15 %. The practical significance of the obtained study results allows to calibrate Raman microscopes and spectrometers on the Raman shift wavenumber scale, as well as to carry out quantitative analysis of individual substances and multicomponent systems using Raman spectroscopy.