Analytical chemistry supercritical water

Solid-phase extractions can reduce solvent consumption in analytical chemistry. For example, a standard procedure approved by the U.S. Environmental Protection Agency for the analysis of pesticides in wastewater requires 200 mL of dichloromethane for the liquid-liquid extraction of 1 L of water. The same analytes can be isolated by solid-phase extraction on C g-silica disks. The pesticides are recovered from the disks by supercritical fluid extraction with C02 that is finally vented into a small volume of hexane. This one kind of analysis can save 10s kg of CH2C12 per year.24... 

Hawthorne SB, Yang Y, and Miller DJ (1994) Extraction of organic pollutants from environmental solids with sub-and supercritical water. Analytical Chemistry 66 2912-2920. 

The supercritical state of water is the most extreme one of common solvents. Its critical temperature Tq is 374 °C and the critical pressure is 22,059 MPa. The properties of liquid and supercritical fluid states are quite different. Supercritical water, e.g., is less polar than liquid water and a solvent for hydrophobic substances. It can be expected that electrochemistry in supercritical water would provide useful information about natural hydrothermal processes, e.g. oxide formation [218]. The majority of research papers, however, were focused on analytical investigations, preferably potentiometric pH measurement [210-212, 216, 219, 220, 253]. The chemistry of different redox couples has been studied as well [223, 224, 226,... 

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