Water-only chemical analysis methodologies: Investigations of water liquid chromatography, subcritical water extraction, and dynamic surface tension detection.

摘要

Investigations into methods for performing chemical analysis using a solvent exclusively of water are demonstrated in the areas of liquid chromatography, solid-liquid extraction, and dynamic surface tension detection (DSTD). These novel methodologies further the attempt to move chemical analysis towards more environmentally friendly techniques through the removal or organic solvents from the analysis step.; Water-only Reversed Phase Liquid Chromatography (WRP-LC) is developed for the separation of organic analytes in a mobile phase of 100% water. To achieve this result, unique stationary phase are chemically bound to the surface of non-porous silica spheres, resulting in a phase volume ratio several orders of magnitude lower than traditional reversed phase stationary phases. Both brush and branched type WRP-LC stationary phases are developed. The brush phase employs an alkylchlorosilane monomer for synthesizing the stationary phase while the branched phase relies on an alkyldichlorosilane, resulting in polymeric structure of greater thickness than the brush phase. As an application, subcritical water extraction (SWE) at 200°C is combined with WRP-LC. This combination automates the extraction of organic compounds from solid matrices immediately followed by liquid chromatographic separation of those extracted compounds, all using a solvent exclusively of water. The use of DSTD for the sensitive and selective detection of surfactants is also reported. It is shown that by forming an ion-pair between an anionic surfactant analyte and a quaternary amine, DSTD sensitivity is enhanced 40-fold over detection of the analyte alone. As a model system, dodecylsulfate and tetrabutyl ammonium hydroxide are used as the analyte and ion-pairing agent, respectively. The flow rate dependence on the sensitivity of detecting the ion-pair was also investigated. Lastly, DSTD and WRP-LC are shown to be effective analytical tools for the direct determination of the binding constant between beta-cyclodextrin and decanesulfonate in water.