Zur Stabilität hochverdünnter Multielement-Eichstandardlösungen — Erfahrungen mit ICP-MS

Summary

The long term stability of self prepared multielement calibration solutions, which is of fundamental importance in ultra trace element analysis with ICP-MS, has been tested. Solutions with element concentrations of 10 ppb, 50 ppb, 100 ppb and 500 ppb in different aqueous matrices have been analyzed immediately after preparation and after 1, 3, 10, and 30 days of stockage in usual glass vials. For analysis with a VG Plasmaquad, the pH of all solutions was adjusted to ca. 1. The results showed that even very low element concentrations of the majority of elements investigated in this study remained stable in acidic aqueous solutions over a period of 30 days. For boron, silver, gold, and tantalum significant changes of the initial concentrations have been observed dependent on stockage time. Decrease of element concentrations is due to adsorption on the surface of the glass vials and probably to photochemical oxidation. A considerable increase of the concentrations of all investigated boron-containing solutions even after a short stockage time is due to mobilization of boron from the glass of the vials. However, adsorption effects are of insignificant importance even for critical elements such as B, Br, I, Pb, and are largely dependent on the pH of the diluted solutions. Solutions with concentrations of a large number of elements in the range even below 1 ppm can be stocked as multielement standards for 30 days, if the pH of the solutions is not higher than 1.