Using scattered light to amplify the photoacoustic spectroscopic signatures of the main absorbing material in a weakly light-absorbing solid mixture

Abstract

Scattered light by the sample is usually one of the main error source in conventional transmission spectroscopy and diffuse reflection spectroscopy. However, scattered light may be useful for photoacoustic spectroscopy measurement. In the present experiment, the photoacoustic spectra of an olanzapine drug tablet and its powder are studied. The olanzapine tablet is a weakly light-absorbing solid mixture and its main constituent is olanzapine. In order to eliminate the background signal produced by the photoacoustic cell wall due to absorbing the scattered light by the sample, the difference between the photoacoustic spectrum of the sample and that of its base is taken and normalized with the photoacoustic spectrum of carbon black. It is found that the photoacoustic spectroscopic signatures of olanzapine in the olanzapine table become obvious when the olanzapine table is powdered. This is the result of the internal light scattering effect in the sample. The scattered light which serves as an obstacle in conventional optical spectroscopy techniques, however, facilitates the photoacoustic spectroscopy measurement. This indicates the particular advantage of photoacoustic spectroscopy. A new method to preliminarily fast identify the main absorbing component in a weakly light-absorbing solid mixture is proposed based on the above experiment. This method can be applied to the field of solid drug and mineral and soil and so on.