Clinio Locatelli

DISTRIBUTION OF MERCURY AND OTHER HEAVY METALS IN CORE SEDIMENTS OF THE NORTHERN ADRIATIC SEA

Seven sediment cores were collected along a transect about20 km off from the mouth of the Po River, in the northernAdriatic Sea (Italy). Cores were characterised by differentdepositional sequences associated with late Pleistocene-Holocene lowstand (LST), transgressive (TST) and highstand (HST) system tracts. Sediment samples were analysed for mercury, copper, nickel, chromium, manganese and iron, aswell as for total organic matter. Metal distributiongenerally showed vertical and spatial variability ascribed tograin size effects with no significant anthropogenicperturbation. Conversely, mercury showed vertical profilescharacterised by surface enrichment, with concentrations inthe upper layer (50–230 ng g-1) exceeding 3–11 times the background value of 20 ng g-1 determined in bottomcores. Surface maxima were attributed to anthropogenic mercurydelivered mainly by the Po River.

Determination of Se, As, Cu, Pb, Cd, Zn and Mn by anodic and cathodic stripping voltammetry in marine environmental matrices in the presence of reciprocal interference. Proposal of a new analytical procedure

Arsenic(III), selenium(IV), copper(II), lead(II), cadmium(II), zinc(II) and manganese(II) have been determined in environmental matrices by differential pulse cathodic (DPCSV) and anodic (DPASV) stripping voltammetry. The voltammetric measurements were carried out using a conventional three-electrode cell and the ammonia–ammonium chloride buffer (pH 9.4) as the supporting electrolyte. The analytical procedure was verified by the analysis of the standard reference materials: Sea Water BCR-CRM 403; Lagarosiphon Major BCR-CRM 060; and Cod Muscle BCR-CRM 422. The precision, expressed as relative standard deviation, and the accuracy, expressed as relative error, were, in all cases, lower than 5%; the detection limits, for each element in the experimental conditions employed, was approximately 10−9 M. The standard addition technique significantly improved the resolution of the voltammetric method, even in the case of very high metal concentration ratios.

Sulfur speciation in mercury-contaminated sediments of a coastal lagoon: the role of elemental sulfur

Chemical equilibrium studies have predicted that elemental sulfur (S0) could play a crucial role in mercury mobility in salt marsh sediments. This prompted us to consider the occurrence of S0 in conjunction with the degree of contamination in sediments of a coastal wetland (Pialassa Baiona, Italy) impacted by inputs of mercury derived from past industrial activity. The distribution of S0, total Hg, soluble sulfates and acid-soluble sulfides was studied in five sediment cores collected in two ponds of the lagoon. Sulfides, sulfates and S0 exhibited vertical profiles typical of salt marsh systems, with concentrations declining with depth. Mercury enrichment (2-23 mg kg-1) was detected at the surface strata where the highest concentrations of sulfides and S0 were found (up to 1.70 and 0.9 g kg-1, respectively). The effect of elevated levels of sulfides and elemental sulfur on the fate of mercury in the lagoon is discussed.

Analytical procedures for the simultaneous voltammetric determination of heavy metals in meals

Abstract An analytical procedure regarding the determination of copper(II), lead(II), cadmium(II), zinc(II) and antimony(III) in matrices involved in foods and food chain as wholemeal, wheat and maize meal is proposed. The digestion of each matrix was carried out using concentrated HCl suprapure at 130 °C for 3 h. Differential pulse anodic stripping voltammetry (DPASV) was employed for simultaneously determining all the elements, using a conventional three-electrode cell and 0.5 M HCl as supporting electrolyte. The analytical procedure has been verified on the reference standard materials Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a and Rice Flour NIST-SRM 1568a. For all the elements in the certified matrix, the precision as repeatability, expressed as relative standard deviation (s r ), and the accuracy, expressed as relative error (e), were of the order of 3 to 6%. The limits of detection were in the range 0.009–0.096 μg/g.

RECENT HPLC STRATEGIES TO IMPROVE SENSITIVITY AND SELECTIVITY FOR THE ANALYSIS OF COMPLEX MATRICES

Recently, various approaches have been addressed to improve chromatographic performance in terms of sensitivity or selectivity, from the development of novel on-line (or off-line) enrichment methodologies, to the improvement of stationary-phase type and multidimensional chromatography, to novel and more performing detectors such as tandem mass spectrometry (MS/MS), nuclear magnetic resonance (NMR), and infrared spectrometry (IR). For the analysis of complex matrices (e.g., biological fluids, plant extracts, food, and environmental samples), coupling chromatographic instrumentation with these detectors provides a powerful analytical device that can be applied in many fields, such as analysis of pharmaceutical and natural products (and medicinal plant), quality control, and environmental trace analysis. This review describes major advances in the HPLC field in terms of enrichment techniques and chromatographic separation, and especially in terms of detector improvement for a complete identification and quantification of targeted analytes. The possibility of high-throughputs analyses, as a consequence of sensitivity and selectivity enhancement in drug and metabolites profile and multi-residue assays for natural compounds and/or products containing natural species, is also highlighted. Finally, it is shown how multivariate analysis may enhance analytical performance in terms of useful analytical information that can be extracted from experimental data and in terms of methods for exploring and modeling data. Chemometrics provides tools for making the most of analytical signals, once selectivity and sensitivity have been improved from the chemical point of view.

Optical spectroscopy of lanthanide ions in Al2O3–Nb2O5–TeO2 glasses

New Al 2 O 3 -Nb 2 O 5 -TeO 2 glasses doped with Er 3+ , Nd 3+ and Tm 3+ were prepared by conventional melt quenching. The absorption spectra were measured and the Judd-Ofelt parameters were extracted. Luminescence spectra in the near infrared region were measured and the values of the stimulated cross sections σ p were evaluated for selected laser transitions. The relatively high values of σ p suggest that these materials can be considered as interesting candidates for optical applications. The spectroscopic behaviour of the lanthanide ions appears to be influenced by the amount of Nb 2 O 5 and Al 2 O 3 in the glass hosts.

Digestion method for the determination of mercury in vegetable matrices by cold vapour atomic absorption spectrometry

A simple and rapid wet-digestion procedure is described for the determination of total mercury in botanical samples by cold vapour atomic absorption spectrometry. The method is based on the oxidising properties of potassium dichromate in dilute sulphuric acid and was tested on two National Institute of Standards and Technology Standard Reference Materials. The mass of the samples taken for analysis was about 0.5 g in all instances, corresponding to an amount of mercury of the order of 0.075-0.040 micrograms depending on the material. The results were compared with those obtained using the Association of Official Analytical Chemists official digestion technique, which involves the use of nitric and sulphuric acids, and a second technique based on the action of nitric and perchloric acids. The proposed method provided better accuracy and showed good precision. Its ability to achieve the decomposition of two organomercurials for full mercury recovery was verified.

A new voltammetric method for the simultaneous monitoring of heavy metals in sea water, sediments, algae and clams: application to the Goro Bay ecosystem.

Arsenic(III), selenium(IV), copper(II), lead(II), cadmium(II),zinc(II) have been determined in sea water, sediments, algae andclams by differential pulse cathodic (DPCSV) and anodic (DPASV)stripping voltammetry. The voltammetric measurements are carriedout using a conventional three-electrode cell and the ammonia-ammonium chloride buffer pH 9.2 as supporting electrolyte.The analytical procedure has been verified by the analysisof the standard reference materials (Estuarine SedimentBCR-CRM 277, Ulva Lactuca BCR-CRM 279 and Mussel Tissue BCR-CRM278). The precision and the accuracy are less than 5%. Thisprocedure is utilized for the monitoring of heavy metals inthe Po river mouth area (Italy).

Cathodic and anodic stripping voltammetry: simultaneous determination of As–Se and Cu–Pb–Cd–Zn in the case of very high concentration ratios☆

Arsenic(III), selenium(IV), copper(II), lead(II), cadmium(II) and zinc(II) are determined in environmental matrices. The voltammetric measurements were carried out using a conventional three-electrode cell and the ammonia-ammonium chloride buffer pH 9.3 as supporting electrolyte. The analytical procedure was verified by the analysis of the standard reference materials Estuarine Sediment BCR-CRM 277 and River Sediment BCR-CRM 320. The precision, expressed as relative standard deviation (s(r)), and the accuracy, expressed as relative error, were, in all cases, less than 5%; the detection limits, for each element and in the experimental conditions employed, were around 10(-9) M. The standard addition technique significantly improved the resolution of the voltammetric method, even in the case of very high metal concentration ratios.

Catalytic-adsorptive stripping voltammetric determination of ultra-trace iridium(III). Application to fresh- and sea-water.

An extremely sensitive stripping voltammetric procedure for ultra-trace determination of iridium(III) is reported. The method is based on the interfacial accumulation of the iridium(III)-CTAB complex onto the glassy carbon electrode, followed by the catalytic reduction of the adsorbed complex in the presence of bromate. 0.3 mol L(-1) acetate buffer pH 4.7+6.9×10(-2) mol L(-1) NaBrO(3)+2.7×10(-5)mol L(-1) cetyltrimethylammonium bromide (CTAB)+0.2 mol L(-1) KCl was employed as the supporting electrolyte. The analytical procedure was verified by the analysis of the standard reference materials: Sea Water BCR-CRM 403 and Fresh Water NIST-SRM 1643d. The accuracy, expressed as relative error e%, was satisfactory, being lower than 6%, while precision as repeatability, expressed as relative standard deviation s(r)%, was generally lower than 5%. The limit of detection was of the order of 2-3 ng L(-1). Once set up on the standard reference materials, the analytical procedure was transferred and applied to superficial water sampled in proximity to superhighway and in the Po river mouth area.