Membrane-based extraction for detection of tastes and odors in water

Abstract

Hollow fiber stripping analysis (HFSA), a modification of closed loop stripping analysis (CLSA), is introduced for the extraction, detection and identification of trace levels of both volatile and low volatility organic compounds in water. The method uses a bank of microporous hydrophobic hollow fiber membranes as the air/water contacting device in a closed, dual-recirculating system. Method design and optimization are presented. Application of membrane extraction for detection of low nanogram per liter (parts per trillion) concentrations of taste and odor causing compounds in water is presented. These compounds can be a particular problem in water as they are detected by water consumers at these very low concentrations, and are perceived as being indicative of poor water quality. Method detection limits, precision and accuracy are presented for four known taste and odor causing compounds. HFSA displays an advantage over CLSA in detection of lower volatility compounds, and in greater reproducibility. HFSA is also able to avoid foaming problems that occur in CLSA during analysis of waters with high surfactant concentrations. Higher volatility compounds are detectable at concentrations similar to CLSA. HFSA is shown to be a reliable, precise and accurate tool for extraction and determination of low nanogram per liter concentrations of low molecular weight organic compounds with dimensionless Henry's Law constants down to approximately 0.001 from a complex natural water matrix.