Giuseppe Scarponi

Direct determination of heavy metals at picogram per gram levels in Greenland and Antarctic snow by double focusing inductively coupled plasma mass spectrometry

The potential of a double focusing ICP-MS instrument in terms of high sensitivity, sample throughput and low volume of sample consumed was investigated for the direct, simultaneous determination of Co, Cu, Zn, Mo, Pd, Ag, Cd, Sb, Pt, Pb, Bi and U at the low and sub-pg g -1 level in polar snow. The entire analytical procedure, including cleaning of material, field sampling, sample handling, determination of the blanks and instrumental analysis, is described. The mean concentrations detected in snow samples collected in Central Greenland (2.7 m deep pit) are (in pg g -1 ): Co 5.8, Cu 4.6, Zn 47, Mo 1.6, Pd 1.1, Ag 0.60, Sb 0.86, Pt 0.61, Bi 2.5 and U 1.8. The Cd, Pb and U concentrations in a snow core section collected in East Antarctica are: Cd 0.39, Pb 5.0, U 0.04 pg g -1 . Repeatability of measurements ranges between 8 and 25% depending on the element considered. For some of the elements investigated these results constitute the first available for polar snow. The results of direct analysis by double focusing ICP-MS on Cd and Pb in the Antarctic snow samples and on Zn and Cu in Greenland samples are consistent with those obtained by differential pulse anodic stripping voltammetry (DPASV) and graphite furnace atomic absorption spectrometry (GFAAS), respectively.

Benthic fluxes of cadmium, lead, copper and nitrogen species in the northern Adriatic Sea in front of the River Po outflow, Italy.

Trace heavy metal (Cd, Pb and Cu) and nitrogen species (N-NO3, N-NO2 and N-NH4) fluxes between sediment and water were examined for approximately 4 days, in a coastal marine station located in the northern Adriatic Sea in front of the River Po outflow. An in situ benthic chamber, equipped with electronic devices for monitoring and adjustment of oxygen and pH and with a temperature detector, was used. The benthic chamber experiment enabled study of the temporal trend of metals and nutrients when oxygen concentration varied in a controlled environment. Although particular care was devoted to chamber deposition and parameter control, sediment resuspension occurred at the beginning of the experiment and O2 fluctuations were observed during the course of the experiment. Pb concentration was affected by both resuspension and oxic conditions in bottom water, which prevented determination of any reasonable Pb flux value. Cd and Cu, not influenced by oxygen fluctuations, reached an equilibrium phase in a short period with initial positive fluxes from sediment of 0.68 (S.D. = 0.07) and 6.9 (S.D. = 5.6) pmol cm(-2) h(-1), respectively. With regard to nitrogen species, the highest positive flux was that of N-NH4 (10.5, S.D. = 2.4, nmol cm(-2) h(-1)) whose concentration increased in the chamber, while nitrate concentration (initial flux of -5.7, S.D. = 1.5, nmol cm(-2) h(-1)) immediately decreased after the beginning of the experiment. Nitrite concentration was almost constant throughout the experiment and its flux was generally low (initial flux 0.1, S.D. = 0.9, nmol cm(-2) h(-1)).

Square-wave anodic-stripping voltammetric determination of Cd, Pb, and Cu in a hydrofluoric acid solution of siliceous spicules of marine sponges (from the Ligurian Sea, Italy, and the Ross Sea, Antarctica)

Square-wave anodic-stripping voltammetry (SWASV) was set up and optimized for simultaneous determination of cadmium, lead, and copper in siliceous spicules of marine sponges, directly in the hydrofluoric acid solution (∼0.55 mol L−1 HF, pH ∼1.9). A thin mercury-film electrode (TMFE) plated on to an HF-resistant epoxy-impregnated graphite rotating-disc support was used. The optimum experimental conditions, evaluated also in terms of the signal-to-noise ratio, were as follows: deposition potential −1100 mV vs. Ag/AgCl, KCl 3 mol L−1, deposition time 3–10 min, electrode rotation 3000 rpm, SW scan from −1100 mV to +100 mV, SW pulse amplitude 25 mV, frequency 100 Hz, ΔEstep 8 mV, tstep 100 ms, twait 60 ms, tdelay 2 ms, tmeas 3 ms. Under these conditions the metal peak potentials were Cd −654 ± 1 mV, Pb −458 ± 1 mV, Cu −198 ± 1 mV. The electrochemical behaviour was reversible for Pb, quasi-reversible for Cd, and kinetically controlled (possibly following chemical reaction) for Cu. The linearity of the response with concentration was verified up to ∼4 μg L−1 for Cd and Pb and ∼20 μg L−1 for Cu. The detection limits were 5.8 ng L−1, 3.6 ng L−1, and 4.3 ng L−1 for Cd, Pb, and Cu, respectively, with td = 5 min. The method was applied for determination of the metals in spicules of two specimens of marine sponges (Demosponges) from the Portofino natural reserve (Ligurian Sea, Italy, Petrosia ficiformis) and Terra Nova Bay (Ross Sea, Antarctica, Sphaerotylus antarcticus). The metal contents varied from tens of ng g−1 to ∼1 μg g−1, depending on the metal considered and with significant differences between the two sponge species.

Cadmium, Lead and Copper Complexation in Antarctic Coastal Seawater. Evolution during the Austral Summer

Abstract The evolution of cadmium, lead and copper complexation by organic ligands was studied along the water column during the 1990/91 summer in the Gerlache Inlet (Antarctica). The complexation was estimated by determination of the total dissolved concentration of metals, the labile concentration, the ligand concentrations and the relative conditional stability constants. The mean value of the total dissolved cadmium concentration was 0.83 nM until mid-December; the concentration was gradually depleted initially in the subsurface layer then down to the bottom. The mean concentration along the water column in February was 0.15 nM. The labile fraction represented 90% of the total until December, and it was reduced to about 20% in the upper 50 m by February. The cadmium was complexed by one class of ligands detectable after mid-December. Initially it was present only in the surface layers and later was extended to the bottom. The ligand concentration reached a maximum (2.2 nM) during the phytoplankton blo...

Determination of very low levels of 5-(hydroxymethyl)-2-furaldehyde (HMF) in natural honey: comparison between the HPLC technique and the spectrophotometric white method.

UNLABELLED In this work we compared 2 official methods for the determination of HMF in honey, the spectrophotometric White method and the HPLC method (International Honey Commission) for the determination of HMF in unifloral honey and honeydew samples with a very low HMF content (<4 mg/kg), which is the most critical determination in terms of accuracy and precision of methods. In honey solutions, the limits of quantification for HPLC and White methods are 0.83 mg/L and 0.67 mg/L, respectively, and the linearity range is confirmed up to 20 mg/L for the HPLC method and up to 5 mg/L for the White method. In honeys with HMF >5 mg/kg, the molar extinction coefficient is 15369, lower than the literature value of 16830, and should be used for HMF determination. For samples with HMF content in the range 1-4 mg/kg the accuracy of the 2 methods is comparable both for unifloral and honeydew samples, whereas as regards precision, the HPLC method gives better results (3.5% compared with 6.4% for the White method). So, in general, the HPLC method seems to be more appropriate for the determination of HMF in honey in the range 1-4 mg/kg thanks to its greater precision, but for samples with a HMF content of less than 1 mg/kg the analyses are inaccurate for both methods. PRACTICAL APPLICATION This work can help governmental and private laboratories that perform food analyses to choose the best method for the determination of HMF at very low levels in unifloral honey and honeydew samples.

Anodic stripping voltammetric determination of the contamination of seawater samples by cadmium, lead and copper during filtration and storage

Summary Anodic stripping voltammetry is employed to investigate the contamination of seawater by cadmium, lead and copper during filtration and storage of samples. Seawater leaches metals from uncleaned membrane filters but, after 1 l of water has passed through, the contamination becomes negligible. Samples stored in conventional polyethylene containers (properly cleaned and conditioned with prefiltered sea water) at 4°C and natural pH remain uncontaminated for 3 months (5 months for cadmium); losses of lead and copper occur after 5 months storage. Reproducibility (95% confidence interval) was 8–10%, 3–8%, and 5–6%, at concentration levels of about 0.06, 2.5, and 6.0 μg l -1 , for cadmium, lead, and copper, respectively. The samples were collected near the coast of an industrial area.

Determination of proline in honey: Comparison between official methods, optimization and validation of the analytical methodology

The study compares official spectrophotometric methods for the determination of proline content in honey - those of the International Honey Commission (IHC) and the Association of Official Analytical Chemists (AOAC) - with the original Ough method. Results show that the extra time-consuming treatment stages added by the IHC method with respect to the Ough method are pointless. We demonstrate that the AOACs method proves to be the best in terms of accuracy and time saving. The optimized waiting time for the absorbance recording is set at 35min from the removal of reaction tubes from the boiling bath used in the sample treatment. The optimized method was validated in the matrix: linearity up to 1800mgL(-1), limit of detection 20mgL(-1), limit of quantification 61mgL(-1). The method was applied to 43 unifloral honey samples from the Marche region, Italy.

SWASV speciation of Cd, Pb and Cu for the determination of seawater contamination in the area of the Nicole shipwreck (Ancona coast, Central Adriatic Sea).

The study reports for the first time on the heavy metal contamination of the waters surrounding a shipwreck lying on the sea floor. Square wave anodic stripping voltammetry has been used for a survey of the total and dissolved Cd, Pb and Cu contents of the seawater at the site of the sinking of the Nicole M/V (Coastal Adriatic Sea, Italy). Results show that the hulk has a considerable impact as regards all three metals in the bottom water, especially for the particulate fraction concentrations, which increased by factors of ≈ 9 (Cd), ≈ 3 (Pb) and ≈ 5 (Cu). The contaminated plume extended downstream for about 2 miles. Much lower contamination was observed for dissolved bottom concentrations; nevertheless Pb (0.56 ± 0.03 nmol/L) is higher than the Italian legal limits established for 2015 and Cd (0.23 ± 0.03 nmol/L) is very close the limit of Cd will be exceeded if the hulk is not removed.

Pb, Cu and Cd distribution in five estuary systems of Marche, central Italy.

Heavy metals are subjected to monitoring in estuarine and marine water by the European Union Water Framework Directive, which requires water body health to be achieved by 2021. This is the first survey of heavy metals content in five estuaries of Marche, a region in central Italy. Results showed that total Pb and Cu concentrations decreased by 70-80%, from 1000-2000 to 100-200 ng L(-1) (Pb) and from 2000-3000 to 500-1000 ng L(-1) (Cu) from river to sea. Cd was consistently 20-40 ng L(-1). Dissolved Pb and Cu concentrations declined by 50% and 70% respectively passing from oligohaline to euhaline water, from 150 to 70 ng L(-1) and from 2000-1000 to 600-400 ng L(-1). Cd decreased slightly from ∼20 to ∼10 ng L(-1). Although such concentrations are in the range allowed by the Water Framework Directive, they far exceed (up to 10×) the ground content ceiling set for 2021.

Microwave-Assisted Solvent Extraction of Melamine from Seafood and Determination by Gas Chromatography–Mass Spectrometry: Optimization by Factorial Design

Melamine attracts considerable attention because of its toxicity. The determination of melamine in seafood was performed by gas-chromatography–mass spectrometry, using an optimized version of a method adopted by the U.S. Food and Drug Administration. The melamine was extracted by closed-vessel microwave-assisted solvent extraction (MAE), as a valid alternative in sample preparation, to reduce analysis time and provide less ambiguous data. The procedure was optimized by means of experimental factorial design considering the three main variables that affect this process: microwave oven power, the maximum temperature inside the extraction tube, and the hold time. The recovery of melamine in spiked samples was used as the elemental response value of the design. Temperature and hold time had a more positive effect on the response than the microwave power. A significant positive interaction was observed between oven power and hold time. A temperature of 70°C and a hold time of 1 min gave a recovery of 92 ± 5% for a microwave power of 600 W. Under these conditions, the total microwave extraction time was approximately 2 minutes, a much shorter time compared to the ultrasonic bath, which required a total time of 40 min. The repeatability of the method was approximately 3%. The limits of quantification were 0.55 mg kg−1 for MAE and 1.9 mg kg−1 for the ultrasonic bath; the linearity was confirmed up to 10 mg kg−1. In conclusion, the MAE procedure was shown to be an excellent alternative to the official method.