The Concentration of Model Organic Compounds Present in Water at Parts-per-Billion Levels using Supercritical Fluid Carbon Dioxide

Abstract

Although hundreds of organic compounds have been identified in samples of natural waters, substantial amounts of the organic matter present cannot readily be characterized using current analytical techniques. Without such prior identification of the substances, they cannot be purchased or synthesized for use in the preparation of the concentrated solutions required for conducting health effects research.

We are conducting an evaluation of the use of supercritical fluid carbon dioxide to isolate and concentrate trace-level organics from aqueous samples. The use of carbon dioxide to effect concentration avoids the introduction of organic solvents or contaminants associated with other methods which may interfere with subsequent biological tests. Twenty-three organic substances have been chosen as representative of classes of compounds usually encountered in aqueous systems. We discuss herein the initial results obtained when aqueous solutions of fifteen of those organic compounds were extracted. The organics were added to water at parts-per-billion concentration levels; some inorganic salts were also added to the solutions to mimic natural waters. The technique has been demonstrated to work for most of the organics studied.

Key Words:

• Concentration
• organics
• trace levels
• supercritical fluid carbon dioxide