Keeping track of evaporating solutions to maintain traceability

In chemical analysis the use of standard solutions is instrumental to guarantee traceability of measurements, however, they could be at risk of suffering solvent evaporation during long storage periods consequently affecting the certified mass fraction of the element/compound of interest. In this work, a measurement model is presented with the aim to take into account this behavior and retain metrological traceability. The proposed strategy revolves around the evaluation of solvent evaporation by just subsequent weightings at the start and end of the storage period. This formulation, iteratively applied, is suitably applicable to three different experimental setups depending on the available information. Multiple simulations and measurements were performed in order to test the model and give an estimate of the expected value and combined variance (thus assessing the increased uncertainty exclusively due to the application of the model). Both strengths and drawbacks were finally pointed out for the proposed model by the reported results, although a conclusive validation with Neutron Activation Analysis was not possible due to the magnitude of the investigated process which makes it highly challenging to quantify. General considerations were finally drawn with recognition of the limitations of the proposed modelization and the great importance reserved to the knowledge of matrix interactions.