The work contained within this dissertation focuses on the use of supercritical carbon dioxide (CO2) in the field of separation science, particularly with regards to the preparation of materials for sample preparation and greenness of supercritical fluid chromatography (SFC) as a separation technique. Supercritical CO2 was utilized in supercritical antisolvent (SAS) precipitation to fabricate a carbon sorbent from micronized polyacrylonitrile (PAN) for use in solid phase extraction (SPE). Additionally, improvements were suggested for the Analytical Method Greenness Score (AMGS) calculator so that the greenness of CO2-containing mobile phases could be assessed more accurately. Furthermore, an additional safety metric was developed to account for solvent release in the event of a leak during SFC analysis. Finally, recommendations for improving the greenness of SFC methods are outlined. The potential of using supercritical antisolvent precipitation for the fabrication of a carbon sample preparation sorbent was explored. Operating conditions, such as pressure, temperature, solution concentration, and CO2 mole ratio, for SAS precipitation were varied to study their effect on the morphology of micronized PAN. Stabilization and carbonization methods were examined to ensure that the morphology of the product was maintained, while maximizing the surface area. The performance of the PAN-based carbon material as an SPE sorbent was studied using a mixture of atrazine, an herbicide, and its degradation products. The solvents needed to effectively condition the sorbent and elute the desired analytes were studied and compared to a commercial carbon sorbent, allowing insight into the interactions available on the PAN-based sorbent. In addition, the greenness of CO2 in separation processes was studied. The AMGS calculator attempts to account for CO2-containing mobile phases, however, several improvements are needed to assess greenness more accurately. Here, EHS scores are al (open full item for complete abstract)

Part I Dibenzotetraaza (DBTA) crown ethers were prepared from benzimidazole. They are tetraaza analogues of dibenzo crown ethers, containing o-phenylenediamine moieties. Overall yields were generally high. No high-dilution conditions were required for the ring-closing step. Unsubstituted crown ethers ranging from 18-crown-6 to 42-crown-14 were prepared and characterized. They are stable under ambient conditions. The synthesis was extended to include crown ethers with modified ether bridges (i.e.; bridges containing sulfur, and catechol-, and 2,3-naphtalenediol-moieties). Crown ethers with substituents at the aromatic rings were prepared. Compounds with electron-donating substituents were obtained as stable solids. Compounds with strongly electron-withdrawing substituents are prone to oxidation, especially in solution. Several benzimidazolidine crown ethers were synthesized. They are DBTA crown ether analogues with methylene-bridges between neighboring nitrogen atoms. The N-alkylation of unsubstituted DBTA crown ethers was investigated. Direct alkylation with alkyl iodides proceeded smoothly in the presence of K2CO3. Tetra(N-organyl) crown ethers are stable under ambient conditions. X-ray crystal structures were obtained for three macrocycles. The general synthesis was also applied to the formation of N, N'-diorganyl-o-phenylenediamines. They were sensitive towards oxidation. Unsubstituted and tetra(N-alkyl) DBTA crown ethers were included in corrosion protection studies of certain steels and aluminum alloys. They were not as effective as commercially available crown ethers. Picrate extraction studies were performed to determine the complexation ability of some representative benzoaza crown ethers. Within the group of metals tested, tetra(N-methyl)DBTA-18-crown-6 extracted moderate to high amounts of all alkaline earth-, transition-, and lanthanide- metal ions. The N-H crown ethers tested showed good selectivity, with high extraction values for Pb2+, and somewhat sma (open full item for complete abstract)