Precise carbon isotopic ratio analyses of micro amounts of carbonate and non‐carbonate in basalt using continuous‐flow isotope ratio mass spectrometry

Abstract

The measured δ C values decrease substantially at lower carbon concentration and higher sample weights, and poorer precision is obtained. Suggestions are made to measure repeatedly the same carbon concentration of sample and reference materials in order to obtain not only reproducible, but also accurate carbon isotope ratios.

USGS44, a new high‐purity calcium carbonate reference material for δ13C measurements

“…Considering the need for high‐precision δ 13 C analysis to normalize small samples, such as in the analysis of foraminifera 39,40 and basalt, 41 carbonate RMs must be well homogenized 30 . Several studies have demonstrated that using an isotope‐ratio mass spectrometer with a GasBench can achieve high‐precision δ 13 C analyses, 38,40–45 and methods for analyzing microgram masses of carbonate have been in use for decades 38,41,43 . For this reason, we carried out homogeneity tests with a GasBench as specified above at the RSIL and a MultiCarb system at Geotop.…”

“…The overall standard deviation of 0.07 mUr from the nine bottles with 26 analyses at 0.10-mg of USGS44 is slightly higher than 0.05 mUr from 0.70-mg analyses of USGS44, and this is thought to be caused by a variable carbon blank from the tin capsules. The average δ 13 C value of −40.08 mUr from USGS44 in Table 3 is the result of singlepoint normalization against NBS 19. Considering the need for high-precision δ 13 C analysis to normalize small samples, such as in the analysis of foraminifera 39,40 and basalt, 41 carbonate RMs must be well homogenized. 30 Several studies have demonstrated that using an isotope-ratio mass spectrometer with a GasBench can achieve high-precision δ 13 C analyses, 38,[40][41][42][43][44][45] and methods for analyzing microgram masses of carbonate have been in use for decades.…”

“…The average δ 13 C value of −40.08 mUr from USGS44 in Table 3 is the result of singlepoint normalization against NBS 19. Considering the need for high-precision δ 13 C analysis to normalize small samples, such as in the analysis of foraminifera 39,40 and basalt, 41 carbonate RMs must be well homogenized. 30 Several studies have demonstrated that using an isotope-ratio mass spectrometer with a GasBench can achieve high-precision δ 13 C analyses, 38,[40][41][42][43][44][45] and methods for analyzing microgram masses of carbonate have been in use for decades. 38,41,43 (Table 3) at the 0.10-mg level, the higher uncertainty of USGS44 obtained with the GasBench probably does not reflect the true material homogeneity, but rather the uncertainty of the analytical method.…”

“…30 Several studies have demonstrated that using an isotope-ratio mass spectrometer with a GasBench can achieve high-precision δ 13 C analyses, 38,[40][41][42][43][44][45] and methods for analyzing microgram masses of carbonate have been in use for decades. 38,41,43 (Table 3) at the 0.10-mg level, the higher uncertainty of USGS44 obtained with the GasBench probably does not reflect the true material homogeneity, but rather the uncertainty of the analytical method. We suspect that small variable amounts of atmospheric CO 2 (δ 13 C VPDB value $ −8 mUr) were introduced into sample vials when purging the samples, which affects the δ 13 C value of USGS44 (δ 13 C = −42.21 mUr) more than that of NBS 19 (+1.95 mUr).…”

Application of Chemometrics for Coal Pyrolysis Products by Online py-GC×GC–MS

“…The repeatability of the total analytical procedure is in the range of 0.1−0.2‰. The experiments are conducted following the analytical method described in Zha et al 51 The δ 13 C VPDB values of coal samples are presented in Table 1.…”