Determination of hydrogen, carbon and oxygen isotope ratios of ethanol in aqueous solution at millimole levels.

Three stable isotope ratios, D/H, (13)C/(12)C and (18)O/(16)O, are measurable in ethanol, an important organic compound that is used as a material for food and beverages, fuel and chemical feedstock, and as a substance related to metabolism. We developed a simple and rapid method of measurement of three isotope ratios of ethanol in aqueous solution at millimole levels using gas chromatography-high-temperature conversion or combustion-isotope ratio mass spectrometry (GC-TC/C-IRMS) combined with solid-phase microextraction (SPME). Using this method, the delta value for ethanol was determined in 30 min for deltaD and delta(13)C, and in 75 min for delta(18)O with precisions of +/-9 per thousand, +/-0.3 per thousand and +/-0.7 per thousand, respectively, for deltaD, delta(13)C, and delta(18)O. An advantage of this process is that it requires no distillation for ethanol purification. The method is useful for small quantities of analyte with low ethanol concentrations, which is expected for environmental and metabolic studies.