Microanalytical flow-through method for assessment of the bioavailability of toxic metals in environmental samples.

The application of a recently proposed microanalytical flow-through system for on-line sequential extraction of heavy metals from solid samples of environmental interest is described. Using various extraction schemes (a nitric acid scheme, a two-stage extraction scheme using two reagents applied in the BCR procedure) and comparison with the common batch sequential BCR procedure, the suitability of the system for fast screening of solid environmental samples is demonstrated. By pumping leaching agents sequentially through the sample held in a micro cartridge, the different metal fractions present can be assessed in less than an hour. Method evaluation was performed using SRM 1648 urban particulate matter and BCR 701 lake sediment reference material certified for extractable metals. The need for and design of laboratory internal reference material suitable for simulating the natural (dynamic) processes of metal release into the environment is also discussed. For the first time correlation is sought between fractionation techniques and physiologically based methods for assessment of the bioaccessibility of metals in biomatrices.