Superheated water extraction (SWE) coupled on-line with superheated water chromatography (SWC)

Since the inception of analytical superheated water extraction (SWE) by Hawthorne and co-workers in 1994, this technique has been widely employed in the extractions of organic pollutants, pesticides, natural products as well as inorganic compounds from a variety of sample matrices. The rapid development of SWE has led to the direct combination of this technique with conventional chromatographic methods. However, these coupling methods still required a considerable amount of organic solvent. In this study, SWE has been directly coupled to superheated water chromatography (SWC) by using simple switching valves and a solid-phase trap as the interface between the extractor and the chromatograph. The trap column was used to collect the extracted analytes and pre-concentrate them prior to chromatographic analysis. It could also be used as a clean-up step for the removal of the matrix interferences from the extract. Because superheated water was used as the extractant, as the mobile phase, as well as the washing solvent, the use of organic solvent has been avoided in all stages of this on-line SWE–SWC method, and therefore it is compatible with 'green chemistry'. [Continues.]