The role of analytical methods for the determination of trace elements in environmental biomonitors

Lichens are currently used as bioindicators to monitor air pollution and to follow changes in pollution patterns. In order to perform reliable biomonitoring, the analysis should be accurate, which implies that a good quality control system should be applied. One way to achieve accuracy is to use analytical procedures validated with certified reference materials (CRM) and tested on real samples by comparing different instrumental techniques. In this paper, a microwave digestion procedure developed for determining several elements in lichen samples by ICP-OES, GFAAS and ICP-MS is described. Among other usual mixtures of attack (HNO3, and H2O2) it also includes the use of HF in order to assure the complete solubilization. of atmospheric particulate or soil dust present on the surface of biomonitors. The method was tested on CRM 482 Pseudovernia furfurea, with good recoveries for approximately 20 elements, and by analyzing real samples in different laboratories with different analytical techniques. The aim of the present work was to demonstrate that the enrichment factor (EF) used in biomonitor programs can be estimated in a correct way only adopting a complete solubilization of the lichen samples, which assures accurate results independently from the presence of atmospheric particulate of different origin and morphology.