Determination of methyl tert-butyl ether in gasoline: a comparison of three fast methods based on mass spectrometry.

A high-speed quantitative analysis of methyl tert-butyl ether (MTBE) using three different methods with mass spectrometry detection has been performed. The first method is based on fast chromatography and required an analysis time of 5.23 min per sample, although a certain period (6 min) was necessary for the initial measurement conditions to be regained prior to analysing the next sample. The other two are non-separative methods and are based on direct injection and headspace generation. The analysis times were 1.5 and 3.5 min, respectively, although in the latter case an additional period of time was required to extract volatiles from the sample. The analytical characteristics of all three methods are highly satisfactory in terms of linearity, lack of fit, precision and accuracy. The methods were applied to the determination of MTBE in different gasoline samples. The non-separative methods afforded slightly higher concentrations than those found when fast chromatography was used; this is due to the presence of other minor components that contribute to the abundance of the ion at m/z 73, characteristic of MTBE. We propose a correction that removes this error very satisfactorily and allows the same results to be obtained with all three methodologies proposed.