| Two different techniques, electrospray ionization mass spectrometry (ESIMS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, were used for the detection and quantification of low concentrations of aqueous anions. Some of these anions, including perfluoroalkanesulfonates (PFAS -), perchlorate, phosphonates, and cyanide, are of interest given that they may cause human health problems and/or persist in the environment. PFAS- anions were quantified in aqueous solution by ESIMS with a detection limit for perfluoro-n-octanesulfonate (PFOS -) of 6 nM. Quantification of PFOS- in the groundwater from wells at a fire-training area at Wurtsmith Air Force Base (WAFB), Oscoda, MI was possible using the method of standard additions as well as linear calibration curves that ranged from 0.01 to 5 muM PFOS -. It is probable that the observed PFAS- anions were components of some of the fire-fighting materials, aqueous film-forming foams (AFFFs), used at this site until 1993. Concentrations of PFAS - anions up to 0.6 muM were detected in the groundwater despite a minimum of five years since active fire-fighting activity ceased at WAFB.; A new ATR-FTIR method was developed for the detection and identification of low concentrations of aqueous polyatomic anions. The technique involves coating the surface of an ATR crystal with a thin-film coating of an organometallic ion-exchange extractant, which enabled anion detection limits to be lowered up to 23,000-fold below those achieved using the commercially available ATR-FTIR spectrometer with an uncoated ATR crystal. Detection limits, for 10-minute analyses of perchlorate, chlorate, trifluoromethanesulfonate, perfluoro- n-butanesulfonate, perfluoro-n-octanesulfonate, pinacolylmethylphosphonate, and cyanide were 0.03, 0.2, 0.05, 0.07, 0.06, 0.7, and 0.09 muM, respectively, using coated ATR crystals. Linear calibration curves based on d(absorbance)/dt, which is related to the rate of anion exchange, were established in the 0.04-30 muM range. Several complex matrixes, including synthetic tap water, simulated seawater, and hydroponic fertilizers, were examined. Using the method of standard additions, trace quantities of perchlorate were detected in hydroponic nitrate fertilizers where the nitrate to perchlorate concentration ratios were as high as 9,000. This simple ATR-FTIR detection/quantification method afforded good reproducibility with relatively fast (10-minute) detection times. |
