Integrating Continuous-Flow Mass Spectrometry and Automatic CO₂ Collection for AMS

Abstract

ABSTRACT. Accelerator mass spectrometry (AMS) radiocarbon measurements of organic samples require combustion to obtain CO 2 for graphitization. Furthermore, determination of δ 13 C values is required in order to correct the 14 C age due to carbon isotope fractionation effects. δ 13 C analysis is commonly carried out by stable isotope mass spectrometry because most applications demand high-precision δ 13 C values in addition to the requirements of 14 C dating. A simplifying step is therefore to combine the combustion for stable isotope analysis with cryogenic trapping of CO 2 for AMS graphite targets. Presented here is a simple CO 2 trapping device based on a modified Gilson 220XL sampling (manifold) robot coupled to the inlet manifold system of a GV Instruments IsoPrime stable isotope mass spectrometer. The system is capable of batch combustion and analysis of up to 40 samples and is under full computer control by the mass spectrometer software. All trapping parameters such as flush time prior to trapping and total trap time are adjustable through the standard software user interface. A low 14 C activity of background materials and high precision and accuracy of stable isotope analysis of carbon and nitrogen are demonstrated.

Atomic spectrometry update. Atomic mass spectrometry

“…The 41 K + and 88 Sr + signals were used to correct interferences of 40 K + on 40 Ca + and 88 Sr 2+ on 44 Ca + , respectively. By using the natural calcite sample MEX, in which the d 44 Ca values had been determined by TIMS, as calibration standard in SIMS analysis, the d 44 Ca value measured in the BRET sample agreed to within experimental error with the value determined by TIMS. The analytical precision was sufficient for measurement of the intra-shell variability of d 44 Ca in planktonic foraminifera.…”

“…By using the natural calcite sample MEX, in which the d 44 Ca values had been determined by TIMS, as calibration standard in SIMS analysis, the d 44 Ca value measured in the BRET sample agreed to within experimental error with the value determined by TIMS. The analytical precision was sufficient for measurement of the intra-shell variability of d 44 Ca in planktonic foraminifera. + projectiles at 44 incidence angle together with oxygen flooding.…”

“…A simple CO 2 trapping device was coupled between an EA and the inlet manifold of a SIRMS instrument in order to collect samples for AMS analysis. 44 In this way a single combustion step provided samples for the determination of both d 13 C, required to correct for fractionation in the AMS analysis, and 14 C by SIRMS and AMS, respectively. The system, capable of batch combustion and isotope analysis of up to 40 samples, was fully automated under the control of the SIRMS software.…”

Rafter radiocarbon sample preparation and data flow: Accommodating enhanced throughput and precision

“…The reactor is packed with chromium oxide, copper oxide and silver wool, and subsequently removes nitrogen oxides using copper at 680°C and removes water using magnesium perchlorate. With the column switch valve set to use the CO 2 collection device, helium carrier gas flows through a split as previously developed for interfacing an EA with an IRMS and cryogenic CO 2 collection for 14 C [7]. In our system, one percent of the CO 2 flows through a 40°iso-thermal capillary GC column (0.32 mm diameter, 30 m length, PLOT active phase) and onto the IRMS.…”

“…The device will be valuable for both conventional dating and C-cycle studies, and has proved useful for the production of a large number of standards and intercomparison samples for the comparison of performance across AMS systems. Based on the reliable history of EA-IRMS for stable isotope measurement and similar development in other laboratories [7], the EA is believed to be appropriate for all samples known to combust well for stable C isotope measurement. Further testing will be required to establish a lower limit in sample size for EA samples.…”