Composition analysis of scattering liquids based on spatially offset visible-near-infrared spectroscopy.

Spatially offset visible-near-infrared (VIS-NIR) spectroscopy was used to analyze of chemical compositions of the scattering liquids in the visible and near-infrared region from 530 to 930 nm. An experimental setup was designed based on a supercontinuum white-light laser source, an electrically controlled translation stage, and a high-performance spectrometer. The spatially offset spectra of the scattering liquids (composed of diluted Intralipid(®) 20% in distilled water) were measured at 24 sequential positions in the radial distribution from the incident light. A partial least squares regression method was applied to obtain the Intralipid(®) concentration from the spatially offset spectra. The results showed that the prediction accuracy of the Intralipid(®) concentration obtained from the spectra collected at multiple sample points was better than that obtained from the spectra collected at a single sample point. The coefficient of determination in the prediction set is 0.9835 at the optimized number of sample points.