Metal pollution of soils is widespread across the globe, and the clean up of these soils is a difficulttask. One possible remediation technique is ex-situ soil washing using chelating agents. Ethylenediaminetetraacetic acid (EDTA) is a very effective chelating agent for this purpose but has the disadvantage that it is quite persistent in the environment due to its low biodegradability. The aim of our work was to investigate the biodegradable chelating agents [S,S]-ethylenediaminedisuccinic acid (EDDS), iminodisuccinic acid (IDSA), methylglycine diacetic acid (MGDA), and nitrilotriacetic acid (NTA) as potential alternatives and compare them with EDTA for effectiveness. Kinetic experiments showed for all metals and soils that 24 h was the optimum extraction time. Longer times only gave minor additional benefits for heavy metal extraction but an unwanted increase in iron mobilization. For Cu at pH 7, the order of the extraction efficiency for equimolar ratios of chelating agent to metal was EDDS > NTA> IDSA > MGDA > EDTA and for Zn it was NTA > EDDS > EDTA >MGDA > IDSA. The comparatively low efficiency of EDTA resulted from competition between the heavy metals and co-extracted Ca. For Pb the order of extraction was EDTA > NTA >EDDS due to the much stronger complexation of Pb by EDTA compared to EDDS. At higher concentration of complexing agent, less difference between the agents was found and less pH dependence. There was an increase in heavy metal extraction with decreasing pH, but this was offset by an increase in Ca and Fe extraction. In sequential extractions EDDS extracted metals almost exclusively from the exchangeable, mobile, and Mn-oxide fractions. We conclude that the extraction with EDDS at pH 7 showed the best compromise between extraction efficiency for Cu, Zn, and Pb and loss of Ca and Fe from the soil.

Prion diseases or transmissible spongiform encephalopathies (TSEs) are characterized by the accumulation in the brain of PrP Sc , an abnormal isoform of the host-encoded glycoprotein PrP C . PrP Sc is a reliable marker for the post mortem diagnosis of TSEs but its use as a marker for a pre-clinical blood test has been hampered by the low levels of PrP Sc in blood. We have evaluated confocal fluorescence spectroscopy (CFS) as an ultrasensitive method for the immunological detection of PrP in brain homogenates and blood serum. Using recombinant PrP, we determined the detection limit of our CFS assay to be in the picomolar range which is in the same order of magnitude as the corresponding luminescence immunoassay (Prionics ® -Check LIA). The analytical sensitivity was further investigated using brain homogenates from BSE infected cattle that showed low levels of PrP Sc by Western blot analysis. In these brain homogenates, PrP Sc was detected by confocal fluorescence spectroscopy down to a dilution of 64-fold whereas the luminescence immunoassay was able to detect PrP Sc in brain homogenates diluted down to at least 128-fold suggesting that in this antibody sandwich assay the luminescence immunoassay has a higher analytical sensitivity than confocal fluorescence spectroscopy. We also demonstrated that blood serum is a suitable matrix for a confocal fluorescence spectroscopy based TSE test, and found that serum did not interfere with the detection of spiked recombinant PrP.

No abstract