Automated system for simultaneous analysis of delta C-13, delta O-18 and CO2 concentrations in small air samples

摘要

In this paper we present an automated system for simultaneous measurement of CO2 concentration, delta(13)C and delta(18)O from small (<1 mL) air samples in a short period of time (approximate to1 hour). This system combines continuous-flow isotope ratio mass spectrometry (CF-IRMS) and gas chromatography (GC) with an inlet system similar to conventional dual-inlet methods permitting several measurement cycles of standard and sample air. Analogous to the dual-inlet method, the precision of this system increases with the number of replicate cycles measured. The standard error of the mean for a measurement with this system is 0.7 ppm for the CO2 concentration and 0.05parts per thousand for the delta(13)C and delta(18)O with four replicate cycles and 0.4 ppm and 0.03parts per thousand respectively with nine replicate cycles. The mean offset of our measurements from NOAA/CMDL analyzed air samples was 0.08 ppm for the CO2 concentration, 0.01parts per thousand for delta(13)C and 0.00parts per thousand, for delta(18)O. A specific list of the parts and operation of the system is detailed as well as some of the applications for micrometeorological and ecophysiological applications. Copyright (C) 2002 John Wiley Sons, Ltd. [References: 13]