Evaluation of commercially available reagents as a reference material for intramolecular carbon isotopic measurements of acetic acid

Abstract

These commercially available reagents will be used as RMs in the future for inter-laboratory calibration and/or inter-calibration with another intramolecular isotopic measurement technique, namely quantitative (13) C NMR. In cases where acetic acid is being used as a RM, its storage must be carefully controlled to prevent evaporation.

Analytical method for simultaneous determination of bulk and intramolecular 13C‐isotope compositions of acetic acid

“…Use of this method means that we can avoid the switching involved with a two‐configuration system and the duplication of sample preparation. This study also shows the importance of using intramolecular isotope standards to calibrate novel approaches …”

“…The intramolecular isotope composition can be calculated from the δ 13 C values of CH 4 and CO 2 . To estimate the potential extent of C‐exchange and the isotope fractionation factors associated with the process, we determined the δ 13 C CO2 and δ 13 C CH4 values for eight working isotopic standards samples for which the intramolecular isotopic composition had already been determined using offline pyrolysis . These values are expected to follow the equations shown below: where δ 13 C COOH and δ 13 C CH3 , respectively, denote the isotope compositions for the carboxyl and methyl groups of acetic acid; δ 13 C CO2 and δ 13 C CH4 , respectively, (Eqn. )…”

“…This study also shows the importance of using intramolecular isotope standards to calibrate novel approaches. [17,24] The convenience of this developed method will enable future developments in the determination of the intramolecular isotope composition of important metabolites (pyruvate, malate, etc.). These future developments will be described in later reports.…”

“…To estimate the potential extent of C-exchange and the isotope fractionation factors associated with the process, we determined the δ 13 C CO2 and δ 13 C CH4 values for eight working isotopic standards samples for which the intramolecular isotopic composition had already been determined using offline pyrolysis. [17] These values are expected to follow the equations shown below:…”

“…Therefore, in the former case, additional metabolic factors such as commitment of ethanol and acetic acid to other metabolic reactions, and uptake of ethanol through the membrane, might play a role in the isotope Table 1. Parameters obtained from the linear regression of the curve representing position-specific isotope composition of previously measured standards and pyrolytic products measured in this study for the methyl and carboxyl C-atom positions of acetic acid [17] distribution of acetic acid. In addition, the vinegar samples analysed in this work are from commercial local stores, which implies that their origin cannot be ascertained.…”