A water extraction, static headspace sampling, gas chromatographic method to determine MTBE in heating oil and diesel fuel

A method was developed to determine the fuel/water partition coefficient (K-MTBE) Of methyl tert-butyl ether (MTBE) and then used to determine low parts per million concentrations of MTBE in samples of heating oil and diesel fuel. A special capillary column designed for the separation of MTBE and to prevent coelution and a gas chromatograph equipped with a photoionization detector (PID) were used. MTBE was partitioned from fuel samples into water during an equilibration step. The water samples were then analyzed for MTBE using static headspace sampling followed by GC/PID. A mathematical relationship was derived that allowed a KMTBE value to he calculated by utilizing the fuel/water volume ratios and the corresponding PID signal. K-MTBE values were found to range linearly from 3.8 to 10.9 over a temperature range of 5-40 degreesC. This analysis method gave a MDL of 0.7 ppm MTBE in the fuel and a relative average accuracy of +/- 15% by comparison with an independent laboratory using purge and trap GC/ MS analysis. MTBE was found in home heating oil in residential tanks and in diesel fuel at service stations throughout the state of Connecticut. The levels of MTBE were found to vary significantly with time. Heating oil and diesel fuel from terminals were also found to contain MTBE. This research suggests that the reported widespread contamination of groundwater with MTBE may also be due to heating oil and diesel fuel releases to the environment.