분석 정확도를 높이기 위한 광역조사 라만 및 근적외선 측정 시스템 개발

Abstract

The importance of wide area coverage in the spectral collection of Raman and near-infrared (NIR) spectra for reliable sample representation has been presented in this thesis. In the case of Raman measurement, unsuccessful sample representation might occur due to the fact that the laser illuminates only on tiny spot rather than large sampling area. To solve the issue of sub-sampling problem, a wide area illumination (WAI) scheme capable of illuminating a laser beam to a circular fashion with a 6 mm diameter (coverage area: 28.3 mm2) has been utilized. In addition, the focal length of the WAI scheme is very long (25 cm), so the reproducibility of measurement could be improved due to less sensitivity of placement of the sample with regard to the focal plane. Analytical performance of the WAI scheme was investigated for diverse application areas: a) compositional analysis of naphtha, b) direct composition analysis of active pharmaceutical ingredient (API) in a capsule, c) on-line compositional analysis of etchant solution, d) on-line analysis flying polyethylene (PE) pellets and e) determination of urea concentration in dialysate solutions. When near-infrared (NIR) spectroscopy is intended to analyze solid samples, diffuse reflectance scheme is mostly adopted for spectral collection, despite of potential advantages of transmission NIR measurement. A novel spectral collection strategy, so call wide area transmission (WAT) NIR scheme, has been also proposed in this thesis. It can circularly illuminate a sample area of 29.5 cm2 (diameter: 5 cm) and measure large amount of samples simultaneously by transmission mode. The WAT NIR scheme was used to determine the density of polyethylene (PE) pellets. To substantially improve the reproducibility, a polytetrafluoroethylene (PTFE) disk capable of diffusing a transmitting light nearly perfectly was placed just in front of pellet packing. The resulting prediction error was improved to 0.0009 g/cm3, better than that from diffuse reflectance measurement (0.0011 g/cm3). Diffuser-incorporated WAT scheme has wide applicability for non-destructive analysis of diverse solid samples such as granules and grains.