Sensitive method for determination of methyl tert-butyl ether (MTBE) in water by use of headspace-SPME/GC-MS

A simple and rapid method for the determination of methyl tert-butyl ether (MTBE) in water by headspace-solid-phase microextraction (headspace-SPME) at sub-microg/L concentrations is described. On using a cooled SPME fiber coated with a 75-microm layer of poly(dimethylsiloxane)/carboxene and heating the sample to 35 degrees C, about 4 times more MTBE is extracted compared to SPME extraction with the fiber placed in the water sample. Stable analytical conditions with a detection limit of 10 ng/L are achieved. By use of a sample volume of 4 mL in a 10 mL vial, a sodium chloride content of 10% (w/w), and an extraction time of 30 min, the total time of an analytical cycle was optimized to 39 min. Precise linearity of R2>0.9991 and R2>0.9916 in the calibration range of 20-5000 ng/L and 20-100 ng/L, both in addition to blanks, respectively, and relative standard deviations of 10% (100 ng/L, long-term) and 11% (20 ng/L, short-term) are presented. The recovery is well within the accepted limits of 83-118% at a concentration of 100 ng/L and even close thereto at trace levels of 20 ng/L (96-125%). The data presented for a concentration of 100 ng/L are examined by statistical methods and show results for the T test at the 95% confidence level. Due to the large concentration range covered, the method is well suited for the monitoring of MTBE in the aquatic environment.