Determination of methyl tert-butyl ether in surface water by use of solid-phase microextraction

A new method based on solid-phase microextraction (SPME) has been developed for the determination of methyl tert-butyl ether (MTBE) in surface water at sub-ppb concentrations. The combination of SPME and GC/MS can be applied for the detection of MTBE at low concentrations if limiting factors are optimized. Best results were obtained with a cooled (5 degrees C) 75 mu m poly(dimethylsiloxane)/Carboxen (PDMS/Carboxen, black) fiber at a sample temperature of 18-19 degrees C and a sodium chloride concentration of 25%. Sixty minute extraction time showed the best compromise between time-consuming and effective extraction in a 1.5 mL vial filled with the water sample. The detection limit under the conditions of a defined signal-to-noise ratio of 10:1 is 10 ng/L, and the relative standard deviation for replicate injections of spiked river water (10 ng/L) was 12% (n = 10). The use of MTBE as a fuel additive in Germany has led to detectable concentrations of 7-160 ng/L in water of the Rhine, Elbe, Main, and Oder rivers. The median concentration (n = 7) was 67 ng/L, and the maximum values were observed in the water of the Rhine. MTBE was also detected in rainwater precipitation in the center of Frankfurt/Main at concentrations of 9 and 70 ng/L MTBE. The median concentrations of MTBE in streams and precipitation are six and two times lower compared to values measured in the United States, respectively. The data reflect the less intense use of MTBE in Germany in comparison to the United States.