Stability Of Metal And Non-Metal Ion Standard Solutions

The stability of long-term storage was evaluated for 37 metal standard solutions and 12 nonmetal ion standard solutions. A resin bottle or a glass bottle was used, depending on the kind of the standard solution. In addition, a case where the resin bottle was sealed in an aluminum-laminated plastic bag was also examined. The storage conditions were room-temperature storage and refrigerated storage. In the stability test, the solution mass in the bottle and the mass fraction of the target element or ions in the solution were monitored. Since the solution mass showed a decreasing tendency due to a evaporation of the solvent, the influence of the evaporation on the mass fraction of the target element or ions was evaluated based on the decrease rate of the solution mass. In addition, the stability of the target element or ions was evaluated by calculating the mass of the target element or ions in the standard solution as the product of the solution mass and the mass fraction of the target element or ions, and by estimating the dependence of the mass on the storage period. In consideration of these two evaluation results, the uncertainty of the long-term stability of the standard solution was evaluated.