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Abstract:Microbial community structure plays a significant role in environmental assessment and animal health management. The development of a superior analytical strategy for the characterization of microbial community structure is an ongoing challenge. In this study, we developed an effective supercritical fluid extraction (SFE) and ultra performance liquid chromatography (UPLC) method for the analysis of bacterial respiratory quinones (RQ) in environmental and biological samples. RQ profile analysis is one of the most widely used culture-independent tools for characterizing microbial community structure. A UPLC equipped with a photo diode array (PDA) detector was successfully applied to the simultaneous determination of ubiquinones (UQ) and menaquinones (MK) without tedious pretreatment. Supercritical carbon dioxide (scCO 2 ) extraction with the solid-phase cartridge trap proved to be a more effective and rapid method for extracting respiratory quinones, compared to a conventional organic solvent extraction method. This methodology leads to a successful analytical procedure that involves a significant reduction in the complexity and sample preparation time. Application of the optimized methodology to characterize microbial communities based on the RQ profile was demonstrated for a variety of environmental samples (activated sludge, digested sludge, and compost) and biological samples (swine and Japanese quail feces).

Recovery of precious metals (platinum, palladium, and rhodium) from a solid matrix sample by supercritical carbon dioxide containing a chelating ligand, a tributyl phosphate (TBP), was studied. The effects of temperature, pressure, and static extraction time on the extraction efficiency were investigated. All experiments were performed using a supercritical fluid extraction system at a temperature range of 40-80• C and a pressure of up to 30 MPa. Results showed that addition of the chelating ligand was necessary to extract the metals. Experiments with pure supercritical carbon dioxide result in no extraction of the metals. It has been observed that the extraction efficiency of metals was strongly dependent on temperature, pressure, and static extraction time. 