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 a t 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 opt imized. Best results were obtained with a cooled (5 degrees C) 75 mu m poly (dimethylsiloxane)/Carboxen (PDMS/Carboxen, black) fiber at a sample temper ature of 18-19 degrees C and a sodium chloride concentration of 25%. Sixty minute extraction time showed the best compromise between time-consuming an d effective extraction in a 1.5 mL vial filled with the water sample. The d etection limit under the conditions of a defined signal-to-noise ratio of 1 0:1 is 10 ng/L, and the relative standard deviation for replicate injection s of spiked river water (10 ng/L) was 12% (n = 10). The use of MTBE as a fu el additive in Germany has led to detectable concentrations of 7-160 ng/L i n 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 conce ntrations of MTBE in streams and precipitation are six and two times lower compared to values measured in the United States, respectively. The data re flect the less intense use of MTBE in Germany in comparison to the United S tates.