. Author manuscript; available in PMC: 2018 Nov 7.

Published in final edited form as: Anal Chem. 2017 Oct 18;89(21):11846–11852. doi: 10.1021/acs.analchem.7b03582

Table 2.

Repeatability Test for R¹⁸O (¹²C¹⁸O¹⁶O/¹²C¹⁶O₂), R¹³C (¹³C¹⁶O₂/¹²C¹⁶O₂), and R¹⁷O (¹²C¹⁷O¹⁶O/¹² C¹⁶O₂) with Different CO₂ Concentrations that Correspond to between 2 μg of CaCO₃ and 100 μg of CaCO₃^a

		calculated CaCO₃		R18 ± 1 S.E.		R13 ± 1 S.E.		R17 ± 1 S.E.	cell pressure	cell temperature
standard	n	volume (μg)	R18	(‰)	R13	(‰)	R17	(‰)	(Torr)	(K)
Oztech-1.46 Torr	10	90	0.9877	0.058	0.9984	0.099	1.0109	0.129	10.07	297.58
Oztech-1.09 Torr	10	67	0.9861	0.067	0.9984	0.129	1.0101	0.069	10.06	297.57
Oztech-0.65 Torr	10	40	0.9865	0.067	1.0033	0.105	1.0010	0.248	10.06	297.60
Oztech-0.16 Torr	10	10	0.9910	0.094	1.0385	0.108	0.9239	0.477	10.06	297.59
Oztech-0.03 Torr	10	2	0.9975	0.136	1.0725	0.387	0.8102	2.006	10.07	297.60

CO₂ concentrations are represented by major isotopologue (¹²C¹⁶O₂) concentration. Cell pressure (Torr) and cell temperature (K) are also shown. R¹⁸O, R¹³C, and R¹⁷O are normalized at 10.0 Torr (1333 Pa) in total pressure and 297.65 K (24.5°C) conditions based on the equations of Figures 3a and 4b.