Maurizio Aceto

Determination of metals in wine with atomic spectroscopy (flame-AAS, GF-AAS and ICP-AES); a review

Metals in wine occur at the mg l-1 level or less and, though not directly related to the taste of the final product, their content should be determined because excess is undesirable, and in some cases prohibited, due to potential toxicity. Lead content in wine, for example, is restricted in several states by legislation to guarantee consumer health protection. Of several methods for metal determination, techniques of atomic spectroscopy are the most sensitive and rapid. Most of the elements present in wine can be determined with these techniques, at concentrations ranging from the mg l-1 to the μg l-1 level. Here, inductively coupled plasma-atomic emission spectrometry (ICP-AES), flame atomic absorption spectrometry (flame-AAS) and graphite furnace-atomic absorption spectrometry (GF-AAS) are compared for their characteristics as employed in metal determination in wine.

Speciation of copper and manganese in milk by solid-phase extraction/inductively coupled plasma-atomic emission spectrometry

A speciation method was developed to study distribution of copper and manganese species in cow milk. The method is based upon solid-phase extraction of selective fractions of the analytes, followed by elution and determination by inductively coupled plasma-atomic emission spectrometry (ICP-AES), using it as a flow-injection detector. Fractions detected were cationic, anionic, neutral and casein-bound. A different behaviour is observed for the two metals.

Ion chromatographic separation and on-line cold vapour atomic absorption spectrometric determination of methylmercury, ethylmercury and inorganic mercury

The ion chromatographic separation of methylmercury, ethylmercury and inorganic mercury as cysteine complexes was investigated. The chromatographic apparatus was interfaced with cold vapour atomic absorption spectrometry for detection using an on-line continuous flow cell coupled with a reduction system (sodium tetrahydroborate). The influence of the composition of the eluent (pH, ionic strength, cysteine concentration) and stripping gas flow-rate was investigated. The method was optimized by coupling an on-line preconcentration step. The detection limits, evaluated on 100.0-ml samples, were 2, 10 and 4 ng for Hg, CH3Hg and C2H5Hg, respectively. The method was applied to synthetic mixtures and natural samples (tap water) and furnished satisfactory results.

Determination of copper, cadmium, iron, manganese, nickel and zinc in Antarctic sea water. Comparison of electrochemical and spectroscopic procedures

Abstract Different procedures for the determination of ultratrace metal ions in Antarctic sea water have been adopted and critically compared. The investigated metal ions were Cd, Cu, Fe, Mn, Ni and Zn. Sea water samples were analysed with adsorptive cathodic stripping voltammetry and with graphite furnace atomic absorption spectroscopy. Different treatments, such as UV irradiation, acidification and on-line sample enrichment were adopted and the results for samples collected in different sites and on a vertical profile were discussed and compared.

Simultaneous determination of methyl-, ethyl-, phenyl- and inorganic mercury by cold vapour atomic absorption spectrometry with on-line chromatographic separation

Abstract A fully automated system for on-line high-performance liquid chromatographic separation, reduction and determination by cold vapour atomic absorption spectrometry (CVAAS) of methyl-, ethyl-, phenyl- and inorganic mercury is described. Reversed-phase chromatography on an ODS column and elution with an acetonitrile-water-ammonium tetramethylenedithiocarbamate buffered mixture was investigated with or without ammonium tetramethylenedithiocarbamate precomplexation. A simple glass flow cell, properly designed as an interface between the chromatographic system and CVAAS, is proposed. The influence of the composition of the eluent, reducing solution and stripping gas flow-rate was investigated and optimized in order to obtain better detection limits. The method, applied to synthetic mixtures and natural samples of tap water furnished satisfactory results. It is shown that, with the on-line preconcentration procedure, sub-ng/ml concentration levels can be determined for all the species considered.

Determination of metals in highly saline matrices by solid-phase extraction and slurry-sampling inductively coupled plasma-atomic emission spectrometry

Matrix removal and preconcentration of metals from liquid samples were obtained with a solid-phase extraction/slurry-sampling procedure applied to inductively coupled plasma-atomic emission spectrometry (ICP-AES) detection. A polymeric, adsorbing resin (Amberlite XAD-2), dispersed in the sample, was used for total sorption of analytes previously complexed with a dithiocarbamate ligand. After filtration, the resin was recovered and re-dispersed by means of a non-ionic surfactant; metals retained were determined with the slurry-sampling technique. All parameters were optimised to yield a solution-like signal from the final dispersion.

Flow injection determination of Pb and Cd traces with graphite furnace atomic absorption spectrometry

The preconcentration and recovery of lead and cadmium traces at ng l(-1) level were evaluated in standard solutions and natural aqueous samples using a FIAS (Flow Injection Atomic Spectrometry) apparatus. The method is based on retention of the complex formed between Pb or Cd and 1,2-dihydroxy-3,5-benzendisulphonic acid (Tiron) on a macroporous anion-exchange resin. The recovery of the analytes was obtained by elution with 0.1 M HCl and their determination was performed by Graphite Furnace Atomic Absorption Spectrometry (GFAAS). The detection limits were 9 and 7 ng l(-1) for Pb and Cd respectively. The effects of sample solution pH and composition and of interfering agents as well as reagent purity are discussed. The technique was applied to the analysis of natural waters.

Distribution of minor and trace metals in Carezza Lake (Antarctica) ecosystem

Abstract This paper reports the distribution of a series of metals in natural samples collected at Carezza Lake in Antarctica, during the Italian Expedition in the austral summer 1989/90. The considered elements are: water, sediments and soil sampled from the surroundings of the lake and algae. The determination of the total concentration of the following metals was performed: Al, As, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Zn. In addition, for sediment and soil samples, a speciation study was performed for some metals, namely Cd, Co, Cr, Cu, Fe, Mn, Ni, Zn, using the Tessier procedure.

Mercury Speciation in Biological Samples

Abstract An extraction method is proposed in order to evaluate mercury species in biological samples (e.g. fish, mushrooms). Sulphur-containing ligands have been considered and thiourea was chosen for the optimised extraction procedure according to the best recovery obtained (65.9%, 75.8%, 47.1% and 98.2% for CH3Hg+ C2H5Hg+, C6H5Hg+ and Hg2+ respectively) and the chromatographic performance. Thiourea solutions added to biological samples enabled extraction of organomercury species; the influence of reaction time and recovery yields were evaluated. The proposed procedure, coupled with an on-line preconcentration step, allows to reduce contamination problems and to obtain detection limits at ng/g levels. The method has been evaluate with reference materials (BCR).

Ion-pair reversed-phase high-performance liquid chromatography for trace metal preconcentration followed by ion-interaction chromatography

Abstract Ion-interaction chromatography of Plasmocorinth B (a disulphonated azo dye) complexes of Co(III), Cu(II), Fe(III), Ga(III), In(III), Ni(II), V(V) and Zr(IV) was studied. The behaviour of two different reversed-phase C 18 columns (5 and 10 μm) was compared and an on-line enrichment procedure was developed following the optimization of eluent (pH, ligand concentration, ionic strength and organic modifier). The described technique, applied to the analysis of metal ions at μg/1 levels in natural waters, gave satisfactory precision and accuracy in comparison with inductively coupled plasma atomic emission spectroscopic results.