SOLID-PHASE ENRICHMENT, THERMAL-DESORPTION, AND ION MOBILITY SPECTROMETRY FOR FIELD SCREENING OF ORGANIC POLLUTANTS IN WATER

Semivolatile organic compounds in water can be determined by using field-compatible methods through extraction with alkyl-bonded membranes, vaporization by thermal desorption, and characterization by ion mobility spectrometry (IMS). Water containing phthalate esters at 1-50 ppm was extracted for 1 h as an unstirred solution by direct contact with thin strips of C8-bonded membranes. Vapors released from the strips at 200-degrees-C were analyzed with a hand-held ion mobility spectrometer (IMS). Ion mobility spectra for phthalate esters were comprised of a single intense negatively charged product ion and peaks were well-resolved in spectra for mixtures of four dialkyl phthalates. Mixtures of these phthalate esters showed composite spectra formed through competitive ionizations. Response for a hand-held ion mobility spectrometer was proportional to aqueous concentrations of dimethyl phthalate from 1-50 ppm and detection limits were ca. 0.5 ppm for a 60-min extraction. A solution of 50 ppm of dimethyl phthalate in water saturated with kerosine was used to illustrate potential applications with chemically complex samples.