Fiber-Optic Sensor for Aromatic Compounds in Water Based on Solid-Phase Microextraction and Ultraviolet Evanescent Wave Absorption Spectroscopy

A method is described for the determination of aromatic contaminants in water samples that combines solid-phase microextraction and ultraviolet evanescent wave absorption (UV-EWA) spectroscopy. In this method, the aromatic compounds are partitioned from a 10 mL sample of water into the polymer cladding of a 10 cm length of UV-transmitting fiber. The aromatics are then detected directly in the cladding by EWA spectroscopy. The time required for four BTEX compounds to reach concentration equilibrium between the aqueous phase and the cladding ranges from 12 to 80 min, although we show that quantitative determinations can be accomplished in 30 min. Detection limits for these compounds range from 1 to 18 ppm, with relative standard deviations from 3 to 17%. Finally, preliminary work demonstrates that natural water matrices pose no significant matrix effects and that this method shows promise in determining the total aromatic concentrations of water samples contaminated with gasoline.