Applications of supercritical fluid and pressurized water extraction in herbal and environmental sample studies

As a promising extraction technique, Supercritical fluid extraction (SFE) has been widely applied in natural product and environmental sample studies, while pressurized water extraction (PWE) as a very effective, selective and economical extraction technique in herbal studies was first developed in this dissertation.; In herbal studies, we used SFE and PWE techniques to extract the pharmacologically active terpene trilactones from the leaves of ginkgo biloba L. (maidenhair tree). Ethanol-modified CO2 at 350 atm. and 100°C can complete the extraction in 15 minutes. PWE at room temperature can remove all the terpenoids including bilobalide more effectively and selectively. Leaf samples collected from different locations and at different times were analyzed, and significant variations were observed.; For quick detection of the terpenoids, two simple analytical procedures were developed. One of them is particularly suitable for analyzing commercial ginkgo products, because no boiling, filtration, pH and volume adjustment operations were required. In a dozen commercial ginkgo products, the terpenoids per dose varied dramatically from brand to brand. One liquid product only contained trace amounts of terpenoids.; In environmental sample studies, toluene-modified CO2 was successfully used to extract polycyclic aromatic hydrocarbons (PAHs) from white pine (Pinus strobus) needles. By using an in-cell silica gel plug and a post-oven silica gel column in an innovated SFE procedure, the extraction and primary separation could be accomplished simultaneously. Samples could be directly injected into GC-MS for quantification. To better understand vegetation as an indicator and a sink in atmospheric pollution processes, pine needles from urban and mountain sites, near streets and on campus, fresh and dry fallen, and whole and pulverized were investigated. PAHs accumulated on street-side needles in an urban site showed obvious seasonal variations, and were significantly more abundant than those in mountain samples. Dry and fallen needles were found to be a very important pathway to remove PAHs from the atmosphere. Ambient temperature was found to be the only significant factor affecting the PAH levels, and surrounding conditions and space are likely the most important controlling factors for the accumulation of PAHs on pine needles.