Jan B. Wooten

Characterization of bright tobaccos by multivariate analysis of 13C CPMAS NMR spectra

Univariate and multivariate statistics were applied to characterize cured bright tobacco samples on the basis of their 13C CPMAS NMR spectra and leaf constituent analysis. NMR spectra were obtained for 55 samples selected from a set of 134 samples of graded bright tobacco leaves from crop year 1999. Historical leaf constituent analyses were available for total alkaloids, reducing sugars, total nitrogen, and insoluble ash. In addition, we applied HPLC to quantify the two abundant plant polyphenols, chlorogenic acid, and rutin. Principal component analysis (PCA) and partial least squares (PLS) of the NMR spectra revealed systematic relationships between groups of samples related to these substances and afforded predictive quantitative models for the analyzed constituents. Analysis of the PLS significant variables showed that leaf polysaccharides, alkaloids, and minerals are major determinants influencing the grading of cured bright tobacco leaves.

Functionalized mesoporous SBA-15 silica molecular sieves with mercaptopropyl groups: Preparation, characterization and application as adsorbents

Mesoporous SBA-15 silica molecular sieve has been synthesized, and functionalized with mercaptopropyl groups via incipient-wetness impregnation of (3-mercaptopropyl)-trimethoxysilane. A thorough characterization revealed that the channels of the SBA-15 silica is uniformly lined with mercaptopropyl groups up to a maximum molar percentage loading of ca. 14.8% with respect to the parent SBA-15 silica while retaining the original mesoporosity. The incorporated mercaptopropyl silane groups are chemically bonded to surface silicons associated with the silanol groups of the parent SBA-15 silica and remain intact during various stages of the preparation. The functionalized mesoporous SBA-15 silica materials are hydrophobic, and perform well as adsorbents in removing trace amounts of mercury and cadmium in various gas streams. Adsorption capacity for mercury vapor increases eight-fold from parent SBA-15 silica to the material with 1% molar percentage loading of mercaptopropyl groups, then declines with further increase in the loading of the mercaptopropyl groups. This suggests that the isolated mercaptopropyl groups serve as preferred adsorption sites for mercury vapor.