SUMMARY
Choice of digestion methods
The report in hand concerns an evaluation of potential for horizontal standardisation for the digestion of samples prior to the determination of trace elements covering sludge, soil, treated biowaste and neighbouring fields.
The detailed comparison of standards for the digestion prior to the determination of trace elements demonstrates the possibility of preparing horizontal standards in this field, however
investigation has to be initiated prior to the establishment.
From an environmental impact evaluation perspective the composition derived from either "partial" or "total" digestion is hardly relevant, as the fraction which even under extreme environmental condition will be brought into solution (and made available for plants etc.) is several orders of magnitude lower. Thus for control purposes or for monitoring or evaluation of developments in element concentration, the use of "partial" methods are considered acceptable.
However, it is of vital importance that the methods provide comparable results with a sufficiently high reproducibility for the elements and matter in question.
In many European countries, digestion methods used for solid environmental samples such as waste, sludge and soil are based on the use of aqua regia in accordance with the relevant European and International standards for the different areas. However, in some European countries, e.g. the Nordic countries, the digestion methods are based on the use of nitric acid.
The reason for this choice being the smaller interference effects from using nitric acids on some of the subsequent analytical procedures.
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