UBC Theses and Dissertations
Challenges in the spectrochemical analysis of complex materials Chen, Zhiwen
Raman and infrared spectroscopy offer characteristic molecular vibrational information that enables a rapid quantitative and qualitative analysis of many types of samples. Easy to operate and requiring little sample preparation, these techniques offer great potential for the classification and quantification of complex materials. The research described in this thesis has sought to apply vibrational spectroscopy and multivariate data analysis to tackle a variety of challenging analytical problems. In vitro fertilization has relied purely on embryo morphological appearance to select viable embryos. We explore the potential of Raman spectroscopy to profile embryo metabolism. By analyzing blank culture media, patient samples and bacteria spent media, we establish that Raman spectroscopy does not offer sufficient sensitivity to differentiate used culture media from control. Even using liquid core Teflon-AF 2400 fibre to enhance the Raman signal of aqueous solution, analytical information still lies beneath the sensitivity limit. Turning to a classification problem relative to variance on a larger scale, we investigate olive oil as a complex biomaterial. The adulteration of extra virgin olive oil with cheaper vegetable oils presents a serious food integrity problem. We demonstrate Raman spectroscopy can detect corn, canola, grape seed and walnut oil in extra virgin olive oils from various countries and cultivars, but only at levels greater than 20%. This contrasts with conclusions of many limited studies, suggesting Raman spectroscopy reliably detects a 5% adulterant. Our analysis shows that such high sensitivity relies on olive oils limited to a specific geographic region or cultivar. Bleached kraft pulps represent important economic resources. By referring to wet chemistry, we apply infrared spectroscopy to study alkaline treated bleached eucalyptus kraft pulp. Infrared spectroscopy shows how alkaline treatment modifies hardwood pulp structure. It also classifies bleached hardwood pulps based on species. Despite the natural biological variance presented by this material, we establish that spectroscopic analysis can accurately quantify the contents of hemicelluloses in a large variety of bleached kraft pulps (softwood, hardwood and their mixture) in industry.
Item Citations and Data
Attribution-NonCommercial-NoDerivs 2.5 Canada