Pressurized Water Extraction: Resources and Techniques for Optimizing Analytical Applications

Abstract

Pressurized hot water extraction above and below the boiling point of water has been demonstrated to be an effective analytical technique. However optimization of this type of extraction often is empirical in approach andfails to take advantage of experimental findings in associated fields or theoretical correlations. In this presentation it will be shown that contributions from four areas can be utilized in the design and optimization of hot water extraction processes: (1) scaled-up processing applications, (2) sub-critical water chromatography, (3) solute (analyte) solubility predictive schemes, and (4) increase of analyte flux rates from sample matrices via mass transport design. The selectivity of pressurized hot water extraction can be maximized not only by regulating the dielectric constant of water, but employing principles noted in the four above areas. Fractionation of solutes then becomes feasible using hot water alone, or with the aid of an associated technique, such as supercritical fluid extraction with SC-CO 2 . Examples will be cited of pesticide, essential oil, herbal mixtures, anthocyanins, and hydrocarbon separation using hot water media. The effect of hot water on common food matrices containing lipids/oils, carbohydrates, and proteins will be cited utilizing examples from the literature, and how this effect can be both advantageous or a disadvantage in analyzing food or agricultural samples. Finally, several examples will be presented which illustrate the application of hot water extraction to food and agricultural analyses.