Extending the limit of measurement for dual H and O isotope ratios using thermolysis.

Hydrogen and oxygen isotope ratios are of use to determine the origin of matter. Thermolysis is used to convert matter to H-2 and CO gases, which are the respective substrates for measurement of these two isotope ratios, using isotope ratio mass spectrometry (IRMS). This work was in response to the need for analysis of small invasive insects, requiring a decrease in the limit of measurement for isotope ratiometry of hydrogen and oxygen, while determining both isotope ratios on the same sample. Miniaturization of a thermolysis reactor using commercially available components is presented that results in improvement in the limit of measurement for both hydrogen and oxygen isotope ratios. (delta H-2 was determined on 0.4 mu g of H and delta O-18 determined on 5 mu g of O with precisions of 3 mUr and 0.7 mUr, respectively. To extend the usable sample size range or increase the resolution of sampling gives obvious advantages in forensic and environmental sciences. The technique has been applied to determining the natural origin of Tephritidae fruit flies for which only the wing is suitable for analysis and provides just 60 mu g of material for analysis.