Biosampling for metal speciation

Biosorption: a new rise for elemental solid phase extraction methods

Biosorption is a term that usually describes the removal of heavy metals from an aqueous solution through their passive binding to a biomass. Bacteria, yeast, algae and fungi are microorganisms that have been immobilized and employed as sorbents in biosorption processes. The binding characteristics of microorganisms are attributed to functional groups on the surface providing some features to the biosorption process like selectivity, specificity and easy release. These characteristics turn the biosorption into an ideal process to be introduced in solid phase extraction systems for analytical approaches. This review encompasses the research carried out since 2000, focused on the employment of biosorption processes as an analytical tool to improve instrumental analysis. Since aminoacids and peptides as synthetic analogues of natural metallothioneins, proteins present in the cell wall of microorganisms, have been also immobilized on solid supports (controlled pore glass, carbon nanotubes, silica gel polyurethane foam, etc.) and introduced into solid phase extraction systems; a survey attending this issue will be developed as well in this review.

Use of erythrocyte ghosts for preconcentration in element speciation

A totally new biosorption concept has been tested. It involves the use of a biological membrane with given transport characteristics that encloses a reaction compartment chosen to bind incorporated substances irreversibly. Such a system is an erythrocyte ghost: erythrocytes that are hypotonically lysed can be filled with the desired media and resealed by warming up for 1 h. The transport system exploited is the predominant one in erythrocytes, i.e., the anion transport system with 10(6) channels/cell. Erythrocyte ghosts (in the following simply called ghosts) filled with ascorbate or cysteine as intracellular reductants were compared to unmodified human erythrocytes with regard to their ability to accumulate chromate specifically. Furthermore, the lifetime and behavior of the ghosts with respect to the influence of extracellular Cr(III) were tested. The great similarity found between the ghosts tested and unmodified erythrocytes clearly shows the general applicability of this new biosorption concept which offers possibilities for the biosorption of analytes that cannot be accumulated by unmodified erythrocytes.

Baker's yeast biomass (Saccharomyces cerevisae) for selective on-line trace enrichment and liquid chromatography of polar pesticides in water

Baker's yeast cells (Saccharomices cerevisae) were successfully immobilized onto silica gel and used in the on-line isolation and trace enrichment of desisopropylatrazine, desethylatrazine, hydroxyatrazine, simazine, cyanazine, atrazine, carbaryl, propanil, linuron, and fenamiphos. Since humic and fulvic acids were not coextracted, no cleanup was necessary. The pesticides were spiked at 0.1-1 microgram L-1 in tap water, groundwater, and seawater and were preconcentrated using on-line solid-phase extraction into a yeast immobilized on silica gel precolumn followed by liquid chromatography with diode array detection. All the variables that affect the enrichment step, such as amount of yeast immobilized, dimensions of the precolumn, sample pH, and preconcentration flow rate, were optimized. The degree of selectivity was evaluated by comparing the chromatograms obtained after on-line sample preconcentration on the yeast precolumn with those obtained by on-line solid-phase extraction using a precolumn filled with C18 material. The relative standard deviation for the whole procedure in the determination of the selected pesticides at the 0.3 microgram L-1 concentration level ranged from 1 to 9%, depending on the pesticide and the type of water. Detection limits within the range 0.01-0.5 microgram L-1 were obtained by percolating only 25 mL of water sample without any additional cleanup step.

Determination of chromium in blood and serum: evaluation of quality control procedures and estimation of reference values in Danish subjects

This paper describes analytical methods to estimate environmental and occupational exposure levels of chromium in blood and serum by Zeeman atomic absorption spectrometry. Also reported is an internal quality control procedure involving a combination of an online quality control and subsequent statistical evaluation of the quality control results to evaluate the performance of the analytical methods. The solubilization of the blood by the proteinase Subtilisin A resulted in a recovery of chromium of 106 +/- 4.5%; the uncertainty was approximately 10% at a chromium level of 1 microgram l-1. The detection limit (LOD) for chromium in serum was 0.17 micrograms l-1 and 0.20 micrograms l-1 for chromium in blood. The LODs were sufficiently low for the determination of chromium in a large fraction of reference populations not occupationally exposed. The present study indicates that reference values for chromium in blood and serum are low but within the range in recent investigations, i.e. 0.04-0.35 micrograms l-1 in serum and 0.12-0.34 micrograms l-1 in human whole blood. The fraction of reference values below LOD was between 0.45 and 0.57 for chromium in serum and blood. Consequently, the reference populations were described by distribution free one-sided tolerance intervals and the precision of the estimation of the tolerance intervals was expressed as coverage intervals. The 95% one-sided tolerance limit calculated for chromium in serum was 0.60 micrograms l-1 with the coverage interval (95 +/- 4.8) percent at a probability of 0.95. Thus, the probability was 0.975 that the tolerance interval covers at least 90.2% of the distribution. In addition, the probability was 0.025 that the tolerance interval covers more than 99.8% of the population. It was only possible to calculate the 90% tolerance interval for chromium in blood with the coverage interval at 0.90 probability. The one-sided tolerance interval for chromium in blood was 0.37 micrograms l-1 with the coverage interval (90 +/- 9.9) percent at a probability of 0.90.