RESUMEN

PURPOSE: Chitosan membranes (non-crosslinked, crosslinked, and modified with L-cysteine) were evaluated as sorbents prior to electrothermal atomic absorption spectrometry (ETAAS) determination of total dissolved metal content in surface water samples. METHODS: Different types of chitosan membranes were prepared in the presence or absence of L-cysteine. Chemical parameters for quantitative sorption/desorption of trace analytes have been optimized. RESULTS: The optimal pH for Cd(II), Cu(II), Ni(II), and Pb(II) sorption using L-cysteine-modified membrane is between 7 and 8.5 and coincides with typical surface water pH, allowing in situ preconcentration of analytes without any additional water sample pretreatments. Non-crosslinked chitosan membrane could be used for simultaneous sampling, transportation, and laboratory determination of Hg(II). Determination limits (calculated as 10σ) achieved for total dissolved metal contents are: Cd 0.001 µg/L, Cu 0.02 µg/L, Ni and Pb 0.05 µg/L, and relative standard deviations were 10-15% for all elements at concentration level of 0.05-2 µg/L. The determination limit achieved for Hg(II) was 0.012 µg/L and relative standard deviations at concentration levels 0.015-2 µg/L were within 9% and 15%. CONCLUSIONS: Non-crosslinked chitosan membrane was proposed as an efficient sorbent for Hg(II) preconcentration and determination in river and lake waters; L: -cysteine modified chitosan membrane was recommended for solid phase extraction of Cd(II), Cu(II), Ni(II), and Pb(II) from surface (lake, river, and sea) waters. The application of chitosan membranes as adsorbents for in situ field preconcentration of the analytes and their subsequent determination by CVAAS and ETAAS in water samples has been demonstrated.

Asunto(s)

RESUMEN

Trace metal speciation in seawater from the Bulgarian Black Sea coast was studied in situ by hollow fiber permeation liquid membrane (HF-PLM) and by diffusion gradients in thin-film gels (DGT). The concentrations of Cd, Cu, Ni, and Pb determined by HF-PLM were lower than those measured by DGT, in agreement with their analytical windows, e.g., free metal ions provided by the HF-PLM and dynamic (mobile and labile) species by the DGT. The obtained suite of data was further used to evaluate the bioavailability of these metals to the microorganisms, which was then compared with experimental results of metal uptake to green microalga Chlorella salina. Uptake fluxes of the Cd, Cu, Ni, and Pb to C. salina, were predicted from the measured HF-PLM concentrations and laboratory experimentation in artificial seawater, in agreement with theoretical considerations. The HF-PLM and DGT appear to be promising analytical techniques for speciation and bioavailability studies in complex environmental media and allow improved understanding of the role of different chemical species in metal bioavailability (and impact) in seawaters.

Asunto(s)

RESUMEN

The present study focuses on the biouptake, biotransformations, and toxicity of arsenic species on the marine green alga Chlorella salina in seawater from the Bulgarian Black Sea coast. Exposure to equal concentrations of As(III) or As(V) led to equivalent levels of toxicity and total intracellular arsenic content. Biouptake and toxicity of methylated arsenic species, monomethylarsonate (MMA) and dimethylarsinate (DMA), were approximately three orders of magnitude lower than those for inorganic arsenic species. Seawater enrichment with phosphate (up to 1.3 mg P L(-1)) resulted in a significant reduction of both intracellular As content and toxicity due to As(III) and As(V). In contrast, the toxicity and intracellular content of MMA and DMA were unaffected by the presence of phosphate. We measured the distribution and excretion of intracellular arsenic species, and demonstrated that the release of As(V) and/or As(III), together with the bio-reduction of As(V) and the subsequent methylation of As(III) may be a detoxification mechanism for these algae. The implications of the results with respect to arsenic species bioavailability and toxicity in marine water are further discussed.

Asunto(s)

RESUMEN

A rapid, accurate, and precise method is described for the determination of Pb in wine using continuous-flow hydride generation atomic fluorescence spectrometry (CF-HGAFS). Sample pretreatment consists of ten-fold dilution of wine followed by direct plumbane generation in the presence of 0.1 mol L(-1) HCl and 1% m/v K(3)[Fe(CN)(6)] with 1% m/v NaBH(4) as reducing agent. An aqueous standard calibration curve is recommended for Pb quantification in wine sample. The method provides a limit of detection and a limit of quantification of 0.3 microg L(-1) and 1 microg L(-1), respectively. The relative standard deviation varies between 2-6% (within-run) and 4-11% (between-run) at 3-30 microg L(-1) Pb levels in wine. Good agreement has been demonstrated between results obtained by CF-HGAFS and direct electrothermal atomic absorption spectrometry in analyses of red and white wines within the concentration range of 9.2-25.8 microg L(-1) Pb.

Asunto(s)

RESUMEN

Analytical procedures for electrothermal atomic absorption spectrometric (ETAAS) determination of arsenic in essential oils from lavender (Lavendula angustifolia) and rose (Rosa damascena) are described. For direct ETAAS analysis, oil samples are diluted with ethanol or i-propanol for lavender and rose oil, respectively. Leveling off responses of four different arsenic species (arsenite, arsenate, monomethylarsonate and dimethylarsinate) is achieved by using a composite chemical modifier: l-cysteine (0.05gl(-1)) in combination with palladium (2.5mug) and citric acid (100mug). Transverse-heated graphite atomizer (THGA) with longitudinal Zeeman-effect background correction and 'end-capped' graphite tubes with integrated pyrolytic graphite platforms, pre-treated with Zr-Ir for permanent modification are employed as most appropriate atomizer. Calibration with solvent-matched standard solutions of As(III) is used for four- and five-fold diluted samples of lavender and rose oil, respectively. Lower dilution factors required standard addition calibration by using aqueous (for lavender oil) or i-propanol (for rose oil) solutions of As(III). The limits of detection (LOD) for the whole analytical procedure are 4.4 and 4.7ngg(-1) As in levender and rose oil, respectively. The relative standard deviation (R.S.D.) for As at 6-30ngg(-1) levels is between 8 and 17% for both oils. As an alternative, procedure based on low temperature plasma ashing in oxygen with ETAAS, providing LODs of 2.5 and 2.7ngg(-1) As in levender and rose oil, respectively, and R.S.D. within 8-12% for both oils has been elaborated. Results obtained by both procedures are in good agreement.