Development of a fiber optic REMPI probe for environmental contaminants

Abstract

On-site determination of volatile organic pollutants in ground water supplies is important for remediation. A simple fiber- optic probe suitable for remote analysis using resonance enhanced multiphoton ionization has been developed and is used to determine the toluene concentration in water samples spiked with gasoline via a head space measurement. An optical fiber transmits a high power laser pulse (266 nm) to the sample, ionizing it, and the subsequent ions are collected with a platinum electrode. Measurements take approximately 1.5 minutes to perform, require no sample preparation, and have been demonstrated over distances of five meters. The limit of detection for toluene in water using this probe is 1.54 plus or minus 0.02 ppb (wt/wt). In addition to the 1 + 1 excitation, the feasibility of a 2 + 2 excitation scheme using 532 nm has been investigated.