Evaluation of different samplers and storage temperature effect on the methane carbon stable isotope analysis.

The present work evaluates the efficiency of some low-cost sampler container for a reliable carbon stable isotope analysis of methane. The procedure efficiency was evaluated for five containers, through 91 days, under two storage temperatures (4 °C and 25 °C) and the results are compared against a reference sampler by using univariate and multivariate statistical methods. Based on the univariate (ANOVA and comparison statistical methods) and multivariate (PCA and HCA) statistical methods, it was identified that (i) the isotopic value changes with time and, in this way, must be taken in account when choosing the appropriate sampler and (ii) the lower temperature reduces the isotopic fractionation process and is preferable for the gas sample storage. Among the storage systems, two options were found to be statistically equivalent to the reference container (IsoJar) for a time horizon of 91 days. We found that the exetainer (4 °C and 25 °C) storage systems are statistically equivalent to the reference container IsoJar and, in this way, it could be an alternative for the methane isotopic studies.