Applications of multivariate chemometric methods to spectroscopic problems.

摘要

Multivariate chemometric methods, like partial least squares (PLS) and classical least squares (CLS), offer advantages in accuracy, precision and outlier analysis over classic techniques of spectroscopic analysis. Experimental design is critical to developing quantitative models that have long-term stability.;PLS models to predict borophosphosilicate glass (BPSG) film properties built on one integrated circuit device are not directly applicable to new devices because the underlying device structure alters the reflectance spectrum. The ability of piecewise direct standardization (PDS), subset recalibration and slope and bias correction to produce accurate and precise predictions of boron and phosphorous concentrations and thickness on new devices structures was investigated with different calibration transfer set sizes.;Surface plasmon resonance (SPR) is an extremely sensitive method for observing changes in refractive index. The observed resonance curves can reflect changes in the real refractive index, absorption, film thickness and a superposition of resonances. PLS models were investigated for their ability to predict refractive index due to thermal variation in water and for interpretation of the dynamics of protein adsorption on a hexadecanethiol-gold surface. The response to protein adsorption is more complex than a simple shift, which could lead to errors in determining kinetics with standard resonance angle measurements.;Confocal Raman spectroscopy offers a rapid method of determining the acetaminophen content of uncoated tablets. The stability, accuracy and detection limit of a PLS models built using different sampling techniques was investigated. The PLS models were determined to be limited by reference error.;Attenuated total internal reflection (ATR) waveguides coated with thin films and infrared spectroscopy can be used to detect ppm and ppb levels of organics in infrared absorbing solutions. Molecularly imprinted titanium dioxide was investigated as an analyte selective film for 3-cyanobenzoic acid and 3-hydroxy-2-napthoic acid.;Silica sol-gel films modified with trimethylchlorosilane are selective for non-polar organics dissolved in water. The response of these films to aqueous mixtures of monosubstituted benzenes was investigated. A method of permanently attaching silica sol-gel films to germanium substrates with epitaxial silicon is presented. The germanium waveguide offers improvement in the number of analytes that are detectable.