All the methods of CO2 calibration, chromatography and normalization presented in this work demonstrated several sources of traceability and accuracy loss for the determination of δ(13) C values in ethanol fuel samples by GC/C/IRMS. This work has also shown the importance of using proper CRMs traceable to VPBD that should be compatible and certified using GC/C/IRMS, ideally in a wide range of δ(13) C values. This is important not only for bioethanol fuel samples, but also for many analytes commonly analyzed by IRMS.

GC/IRMS was used to measure the carbon isotopic signature (δ13CV-PDB) of the Brazilian sugarcane bioethanol.

The Brazilian Metrology Institute (National Institute of Metrology, Quality, and Technology, Inmetro) has been developing a certified reference material (CRM) of the volatile organic compounds benzene; toluene; ethylbenzene; and ortho, meta, and para-xylenes (BTEX) in methanol, to ensure quality control for environmental-analysis measurements. The objective of this paper is to present the results of certification studies: uncertainty estimates related to characterization, a homogeneity study, and a stability study on a single lot of CRM composed of BTEX in methanol. The method used analysis of variance (ANOVA), a statistical tool, to evaluate the homogeneity and stability of the BTEX CRM, which complies with ISO Guide 30 series. The homogeneity and stability of the BTEX CRM was confirmed for all analytes and their respective properties. All the procedures used in this study complied with ISO GUIDE 34, ISO GUIDE 35, and the guide to the expression of uncertainty of measurement (GUM).