Multicomponent analysis using a confocal Raman microscope

Abstract

Measuring the concentration of multiple chemical components in a low-volume aqueous mixture by Raman spectroscopy has received significant interest in the literature. All of the contributions to date focus on the design of optical systems that facilitate the recording of spectra with high signal-to-noise ratio by collecting as many Raman scattered photons as possible. In this study, the confocal Raman microscope setup is investigated for multicomponent analysis. Partial least-squares regression is used to quantify physiologically relevant aqueous mixtures of glucose, lactic acid, and urea. The predicted error is 17.81 mg/dL for glucose, 10.6 mg/dL for lactic acid, and 7.6 mg/dL for urea, although this can be improved with increased acquisition times. A theoretical analysis of the method is proposed, which relates the numerical aperture and the magnification of the microscope objective, as well as the confocal pinhole size, to the performance of the technique.

Non-Invasive Blood Glucose Monitoring Technology: A Review

“…Different radicals vibrate in unique ways, generating scattered light at specific frequencies. The types of molecules that make up a substance could be identified by Raman spectroscopy [68].…”

“…R-Square) of 0.91 [71]. Tang et al conducted multi-component analysis with confocal Raman microscope, and quantified physiological glucose concentration by partial least-squares regression method, with the predicted root mean square error (RMSE) of 17.81 mg dL −1 and the linear correlation coefficient of 93% (Figure 5A) [68]. In the latest research, Yang et al proposed that glucose-MPBA (mercaptophenylboronic acid) bonding modifies two of MPBA's Raman modes, resulting in a peak shift whose magnitude can be correlated to the ambient glucose concentration.…”

Improved performance of near infrared excitation Raman spectroscopy using reflective thin-film gold on glass substrates for cytology samples

“…e spreading out of the laser at the gold surface (during recording of a cell spectrum, the laser is focused on the cell nucleus at a point that is at least 1um from gold surface. ), the short penetration depth of light in gold 33 , and the e ect of the confocal aperture 35 all appear to reduce the presence of background spectrum from the gold in the Raman spectrum of the cell.…”