A static headspace GC-MS/MS method for the determination of ethanol, iso-butanol, and n-butanol at nanomolar concentrations in aqueous environmental samples

The increased use of small molecular weight alcohols such as ethanol and potentially butanol isomers as biofuels has raised questions about the fate of these compounds in the environment once emitted. In order to address these questions, a method for the simultaneous determination of nanomolar concentrations of ethanol, n-butanol, and iso-butanol in aqueous environmental matrices is presented. The method consists of static headspace gas chromatograph-mass spectrometer/mass spectrometer (GC-MS/MS) analysis with detection limits of 28 nM for ethanol and 9 nM for each butanol isomer. Accuracy of the new method was verified by comparing ethanol concentrations in authentic environmental samples by an independent technique utilizing solid phase microextraction (SPME). Results of an intercomparison study between the static headspace GC-MS/MS and SPME analyses produced a trend line with a slope of unity demonstrating that the methods produced statistically equivalent ethanol concentrations. Spiked additions of each alcohol in a variety of aqueous environmental matrices gave recoveries greater than 90% validating the accuracy of the headspace GC-MS/MS analysis. The new static headspace GC-MS/MS analysis represents the first methodology available with demonstrated accuracy in an array of environmental matrices with the requisite limit of detection capable of quantifying several alcohols in one analysis with minimal sample preparation and sample size requirement.