Minimization of sample requirement for δ18O in benzoic acid

Abstract

The measurement of the oxygen stable isotope content in organic compounds has applications in many fields, ranging from paleoclimate reconstruction to forensics. Conventional High-Temperature Conversion (HTC) techniques require >20μg of O for a single δ18O measurement. Here we describe a system that converts the CO produced by HTC into CO2 via reduction within a Ni-furnace. This CO2 is then concentrated cryogenically, and 'focused' into the isotope ratio mass spectrometry (IRMS) source using a low-flow He carrier gas (6-8 mL/min). We report analyses of benzoic acid (C7H6O2) reference materials that yielded precise δ18O measurement down to 1.3 μg of O, suggesting that our system could be used to decrease sample requirement for δ18O by more than an order of magnitude. © 2010 John Wiley & Sons, Ltd.