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Bernhard Michalke

Publications and source records attributed to Bernhard Michalke.

3 recordsLinked to original sources
PubMed2003

Element speciation definitions, analytical methodology, and some examples.

This paper gives definitions related to element speciation and the reasons for the need for speciation. The problems focused on, involve sampling, sample preparation and storage, as well as changes in species information that occur during the use of various separation technologies. However, the potential and advantages of the separation methods in element speciation are also discussed. In addition, problems arising during element detection that are attributable to analytes or mobile-phase composition are outlined, as well as the pronounced advantages of detection by inductively coupled plasma-mass spectrometry (ICP-MS). The combination of the various separation systems with element- or molecule-specific detectors creates problems especially in element speciation. These difficulties are described along with recent developments for overcoming them or for improving their coupling efficiency. Finally, several elements for which the issue of speciation is important are discussed, with examples from some recent publications on arsenic, selenium and iodine speciation.

Environmental Monitoring↗
PubMed2003

Optimisation of extraction procedures for metallothionein-isoforms and superoxide dismutase from liver samples using spiking experiments.

The speciation of trace element species in solid matrices like liver samples is still problematic due to two reasons. On the one hand direct methods with sufficient selectivity and sensitivity are currently not available. Therefore extraction procedures have to be applied which are often problematic in respect to species stability. On the other hand there are no reference materials with known amounts of metal proteins like metallothionein-isoforms (MT) and superoxide dismutase (SOD) for quality control. So the aim of this study was to develop and optimise procedures for the species-preserving extraction of the model compounds MT and SOD from liver samples. Spiking experiments were performed to overcome the lack of appropriate reference materials. In a first step the stability of the model species without liver matrix was investigated by the variation of several extraction parameters. The extractant and exposure to ultrasonic energy especially had a great influence on the recovery of the species while temperature, buffer concentration and atmospheric conditions were less critical. In a second step spiked liver samples were extracted with a selection of procedures taken from the literature. Most of these methods provided recoveries between 70% and 100%. Additionally the buffer concentration and the extractant-to-liver ratio were varied for optimisation. The metal balance of an extraction showed recoveries of 81% for Cd, 94% for Cu and 87% for Zn.

Animals↗