We describe a new technique for sample preparation, accelerated solvent extraction (ASE), that combines elevated temperatures and pressures with liquid solvents. The effects of various operational parameters (i.e., temperature, pressure, and volume of solvent used) on the performance of ASE were investigated. The solvents used are those normally used for standard liquid extraction techniques like Soxhlet or sonication. We found the recoveries of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and total petroleum hydrocarbons from reference materials using ASE to be quantitative. The extraction time for 1-30-g samples is less than 15 min, and the volume of solvent is 1.2-1.5 times that of the extraction cell containing the sample. No evidence was seen for thermal degradation during the extraction of temperature-sensitive compounds.

The portable GC-MS system distinguished the treatments based on their detected volatile profiles. Additional statistical analysis identified five possible biomarker volatiles for the treatments, among them cyclosativene and copaene, which indicated damaged flower heads.

This paper compares static (i.e., temporally unchanging) thermal gradient gas chromatography (GC) to isothermal GC using a stochastic transport model to simulate peak characteristics for the separation of C12–C14 hydrocarbons resulting from variations in injection bandwidth. All comparisons are made using chromatographic conditions that give approximately equal analyte retention times so that the resolution and number of theoretical plates can be clearly compared between simulations. Simulations show that resolution can be significantly improved using a linear thermal gradient along the entire column length. This is mainly achieved by partially compensating for loss in resolution from the increase in mobile phase velocity, which approximates an ideal, basic separation. The slope of the linear thermal gradient required to maximize resolution is a function of the retention parameters, which are specific to each analyte pair; a single static, thermal gradient will not affect all analytes equally. A static, non-linear thermal gradient that creates constant analyte velocities at all column locations provides the largest observed gains in resolution. From the simulations performed in this study, optimized linear thermal gradient conditions are shown to improve the resolution by as much as 8.8% over comparative isothermal conditions, even with a perfect injection (i.e., zero initial bandwidth).

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