Slurry Electrothermal Atomic Absorption Spectrometry Research Articles

Slurry sampling electrothermal atomic absorption spectrometric determination of palladium in water using biosorption with inactive baker's yeast Saccharomyces cerevisiae

Inactive cells of yeast Saccharomyces cerevisiae were used for palladium preconcentration. The conditions for biosorption of palladium and its determination in yeast cells by slurry electrothermal atomic absorption spectrometry (ETAAS) were optimised. The best sensitivity of measurements and stability of slurry were obtained by using a mechanical agitation (10 minutes) and a mixture of 0.3 mol l−1 thiourea – 1 mol l−1 HCl – 0.5% Triton X-100 as suspension medium. The repeatability of the measurements of Pd in yeast slurry was 6.5% (n = 10). For the quantification of analyte in spiked water samples, the standard addition method was used.

Determination of selenocystamine by slurry sampling electrothermal atomic absorption spectrometry after a selective preconcentration by living Pseudomonas putida

A method to determine selenocystamine (Se-Cystm) in water samples, containing other selenium species, is proposed. This novel method makes use of living bacterial cells for preconcentration of Se-Cystm prior to the determination of selenium by slurry sampling electrothermal atomic absorption spectrometry (ETAAS). The extraction–preconcentration procedure consists of putting aPseudomonas putida strain in contact with a glucose culture medium supplemented with Se-Cystm. By allowing maximum growth of the bacterial cells to be reached, an equilibrium between the analyte in the solution and in the extractive solid phase is established. Then, discarding the supernatant, the concentration of the organoselenium compound is determined directly in the biomass pellet by slurry ETAAS. The retention procedure was optimized by controlling the growth conditions (amount of glucose, seeding density and growth time). A theoretical model intended for the mathematical modelling of the uptake of Se-Cystm by the living bacterial cells was developed. The theoretical model fits well with the experimental data. This relationship also provides a feasible quantification of the extraction process before the uptake equilibrium is achieved. The determination stage was also optimized by controlling the amount of the chemical modifier used (palladium), as well as the pyrolysis and atomization temperatures. The interference effects from other selenium species [selenoethionine (Se-Eth), SeIV, selenomethionine (Se-Met), selenourea (Se-U), selenocystine (Se-Cyst), SeVI] were also studied. The method is selective for Se-Cystm and it can be used for speciation of this organoselenium compound in the presence of the others. The analytical performances of the developed procedure were established. The detection limit (three times the standard deviation of the blank) and the sensitivity (analyte concentration for an integrated absorbance of 0.0044 s) of the developed approach were of 0.10 and 2.29 ng ml–1 of Se-Cystm, respectively.

Speciation of selenomethionine and selenourea using living bacterial cells†

A novel and reliable method is proposed for speciation of selenomethionine (Se-Met) and selenourea (Se-U) combining a time-controlled solid phase extraction by using living bacterial cells and electrothermal atomic absorption spectrometry (ETAAS) for the determination of selenium. The extraction medium consists of a Pseudomonas putida strain cultivated in a culture medium based on glucose contaminated with an organoseleno compound. Firstly, equilibrium between the analyte in the solution and the retention medium is allowed to be established, and then the concentration of the organoseleno compound is determined directly in the biomass by slurry ETAAS. It is possible to discriminate between different chemical species of selenium by combining the optimization of both the growth conditions and the relative rates of their retention from the sample solution. A theoretical model of the retention process, based on a rate-determining step in reaching the adsorption equilibrium, is proposed to describe the experimental adsorption time profiles of the uptake process by the living bacterial cells. This relationship can also provide a feasible quantification of the extraction process before the adsorption equilibrium is reached, whenever the agitation conditions and the sampling time are under control. The experimental data agreed closely with the theoretical model. The study of the adsorption process was derived to develop an analytical procedure to determine Se-Met and Se-U in matrices containing other selenium species (Se-ethionine, Se-cystamine, Se-cystine and SeVI). The best detection limits for the organoseleno compounds at their optimum extraction times are 1.5 ng ml–1 for Se-Met and 1.2 ng ml–1 for Se-U. The relative standard deviations of the retention/determination process are 2.2–5.6%.

Determination of cadmium in biological and environmental samples by slurry electrothermal atomic absorption spectrometry

The retention of cadmium by the bacteria Escherichia coli and Pseudomonas putida was optimized in order to develop a rapid and selective preconcentration method for cadmium from biological and environmental samples prior to determination by electrothermal atomic absorption spectrometry. Living and lyophilized cells for both bacteria were used, but the method using dead cells shows better analytical capabilities. Cadmium from aqueous solutions is easily retained on the outer membrane of both bacteria in the pH range 4–10, although the selected working pHs for E. coli and P. putida were 5 and 9, respectively. Cadmium retained by the bacteria was dispersed in 3.5 M nitric acid and the slurry was introduced directly into the graphite tube. The best sensitivity and detection limit were obtained for E. coli (0.03 ng ml −1 and 0.04 ng ml −1 respectively, in the absence of any chemical modifier). A strong spectral interference from nickel chloride was found and methods to overcome it were developed. The proposed extraction procedure was tested by the determination of cadmium in different standard biological and environmental samples.

Determination of Cadmium and Lead in Aerosols in the Zasavje Region in Slovenia Employing Slurry Electrothermal Atomic Absorption Spectrometry

Abstract Investigations of air pollution were carried out in the Zasavje urban industrialized region in Slovenia. Cadmium and lead were measured in respirable (< 2.5 μ) and inhalable (2.5–10 μ) aerosols. Special pumps were equipped with a Nucleopore-Costar polycarbonate membrane filters. Cadmium and lead were measured in those filters by slurry electrothermal atomic absorption spectrometry (ETAAS) on a laboratory-assembled atomic absorption spectrometer with a graphite cup atomizer. A reliability of the employed technique was proved by analysis of the same filters with classical dissolution of aerosol particles in diluted nitric acid and measurement of cadmium and lead by flame atomic absorption spectrometry (FAAS). Good agreement (±5–10%) of the results was obtained between the two techniques for both elements. The study indicated that cadmium and lead in a contaminated area prevailed in the respirable (< 2.5 μ) aerosols. The employed technique was sensitive enough for measurement of cadmium and lead also in non-polluted sites.

Influence of slurry preparation on the accuracy of ultrasonic slurry electrothermal atomic absorption spectrometry

The influence of slurry preparation on the accuracy of ultrasonic slurry electrothermal atomic absorption spectrometry has been studied and this technique has been used for very accurate determinations such as the characterization of reference materials. This approach is particularly useful for characterization of the homogeneity of materials at mg and sub-mg levels. Because of the distribution of analyte between the solid and liquid phase of the slurry, a new term (‘representative sample mass’) is introduced to describe what portion of the mass of sample weighed out is represented by the analysis. The suitability of alternative wavelengths is demonstrated and guidelines for optimization of slurry preparation are presented.

Determination of gold by slurry electrothermal atomic absorption spectrometry after preconcentration by Escherichia coli and Pseudomonas putida

The accumulation of gold by bacterial cells and the possibility of using this preconcentration procedure prior to the determination of gold by electrothermal atomic absorption spectrometry were examined. Both batch and immobilization techniques for Escherichia coli and Pseudomonas putida were compared. Best analytical parameters were obtained for E. coli using a slurry sampling technique with sensitivity and detection limits for gold of 0.001 and 0.004 ng ml–1, respectively, using platform atomization.

Determination of lead in soil by slurry–electrothermal atomic absorption spectrometry with a fast temperature programme

A fast temperature programme for the determination of Pb in soil by slurry–electrothermal atomic absorption spectrometry was developed by omitting the charring step and drying at a higher temperature for a shorter time. The effects of drying temperature and time were systematically studied. Work with phosphate and Mg–Pd as chemical modifiers indicates that better results can be obtained without the use of modifiers.