Green sample preparation in analytical separation sciences : electrophoretic concentration

摘要

Traditional sample preparation requires substantial resources and time, both adversely affecting the economical and ecological accounts of an analytical workflow. To address the dearth of greenness, this work used field-enhanced and electrokinetic sample injection from capillary electrophoresis (CE) for off-line sample preparation. This approach, referred to as electrophoretic concentration (EC) and simultaneous EC and separation (SECS), relies on the use of an electric field to transfer charged analytes from a mL-volume of aqueous sample to 20 μL of acceptor electrolyte immobilised in a micropipette. The use of a conductive hydrogel to facilitate a zero net-flow inside a fused silica capillary is described and then explored for EC of charged analytes. The hydrogel was crucial to the success of EC, because it supported voltage application and retained the acceptor electrolyte in the micropipette. Anionic dyes and pollutants from drinking water as well as cationic drugs from wastewater were concentrated in less than 50 min and sensitive analysis by CE was achieved. The EC setup was then modified for SECS and implemented on an eight channel device to increase the sample throughput. Herbicides fortified in river water and beer samples were used to study SECS in combination with chromatographic and electrophoretic separation employing UV and mass spectrometric detection. Analyte enrichments of up to a factor of 337 in less than 45 min were achieved which enabled low ng/mL detection. Compared to solid-phase extraction, SECS reduced the sample preparation time by 94% and resource consumption by 99%. EC and SECS in combination with stacking-CE showed potential for trace analysis and all the SECS and EC acceptor electrolytes were directly compatible for analytical separation without the need for time-consuming steps. EC and SECS were organic solvent-free, rapid and simple sample preparations which were complying with the principles of Green Analytical Chemistry.