Influence of absorption on quantitative analysis in Raman spectroscopy

Absorption of both the excitation and Raman scattered light by the sample (self-absorption) is common in UV Raman spectroscopy and sometimes in visible and FT-Raman spectroscopy due to electronic or vibrational excitation. Self-absorption affects Raman bands and usually results in a non-linear relationship between the Raman intensity and sample concentration. This paper compares quantitative analysis methods for Raman measurements of absorbing liquid and solid samples. Methods based on both internal and external standards can be used to correct for self-absorption. Examples including both liquid (1-methylnaphthalene/isooctane) and solid (V/δ-Al2O3) systems were used to compare the effectiveness of these methods. The results show that as long as certain restrictions on the use of these analysis methods are satisfied, the self-absorption problem in Raman spectroscopy can be accurately corrected.