Chromatographic determination of solubilities in superheated water

• Published in: Journal of separation science 2010-10, Vol.33 (20), p.3107-3109
• Main Authors: Jones, Neil, Clifford, Anthony A, Bartle, Keith D, Myers, Peter
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Aromatic hydrocarbons; Chemistry; Chromatographic methods and physical methods associated with chromatography; Chromatography; Correlation analysis; Eluents; Exact sciences and technology; Extrapolation; General and physical chemistry; Other chromatographic methods; Pollutants; Solubility; Solubility determination; Solutions; Solvents; Superheated water; Toluene
• ISSN: 1615-9306; 1615-9314; 1615-9314
• DOI: 10.1002/jssc.201000343

Superheated water (SHW) is an effective solvent for the extraction of a variety of environmental pollutants, but knowledge of the solubilities in water at elevated temperatures necessary to maximise the efficiency of the process is often lacking. Ambient temperature aqueous solubilities have been measured by reverse-phase HPLC from correlations with retention factors, k, but for poorly soluble organics the eluent must contain a proportion of organic modifier followed by extrapolation to pure water. The use of SHW as mobile phase allows direct determination of aqueous solubility from measurement of k on a modified HPLC system in which the eluent is cooled before detection to improve baseline stability. Alumina-bonded octadecylsilane columns were found to be more stable in SHW chromatography than their silica-bonded counterparts. To validate the procedure, measurements of k were made between 100 and 200°C for toluene and correlated with literature solubilities; the solubilities at 170°C of a number of related aromatics were then determined from their k-values.