Two methods, microwave digestion and dilution in nitric acid solution, are commonly used for the analysis of metals. These two methods employ different sample preparation steps and it is not obvious if one method has advantages over the other.

The CORESTA E-Vapour Sub-Group (EVAP) carried out a study to determine if current in-house laboratory methods were sufficient for the analysis of metals in e-liquids. The results of the study were used to determine if method accuracy is impacted by the choice of sample preparation.

The data suggested that either technique (digestion or dilution) could be used for the determination of metals in e-liquids, although specific attention to detail to reduce potential sources of background contamination is necessary regardless of the technique used.

Based on the simpler sample preparation and equivalency of the study results, the EVAP Sub-Group has decided to plan a future collaborative study using only the dilution method. The goal would be to produce a CORESTA Recommend Method (CRM) for the analysis of metals in e-liquids.