Cristina Lagomarsino

Effect of operating conditions on excitation temperature and electron number density in axially-viewed ICP-OES with introduction of vapours or aerosols

The combined effect of the power and the carrier gas flow rate on excitation temperature, electron number density, ionic-to-atomic line intensity ratios and departure from local thermal equilibrium has been studied in an axially-viewed plasma with introduction of different amounts of wet aerosols, partially desolvated aerosols or dry vapours, according to empirical modelling and experimental design methods. Under robust conditions (1500 W and a carrier gas flow rate of 0.7–0.85 L min−1), an increase in water loading led to an improvement in the plasma excitation properties, while desolvation caused degradation. In contrast, under non-robust conditions, the plasma was no longer able to tolerate an increase in water loading and desolvation resulted in an improvement in the plasma characteristics. The hydrogen formed during the hydride generation process significantly improved the plasma excitation properties, regardless of the conditions. In this instance, the plasma characteristics were primarily affected by the reductant concentration, which determined the amount of hydrogen generated, and by the carrier gas flow rate, which controlled its residence time within the plasma. In contrast, there was no relevant change in the plasma excitation conditions due to systematic variation of HCl concentration from 0.1 to 6 M.

Natural variability and distribution of trace elements in marine organisms from Antarctic coastal environments

Abstract In an attempt to improve the understanding of the natural variability and distribution of trace elements in Antarctic organisms, the concentrations of arsenic, cadmium, cobalt, chromium, copper, manganese, nickel, vanadium and zinc in representative benthic species from two pristine coastal environments were measured and compared with literature data for other uncontaminated coastal ecosystems. Correlations between the elements, differences between the species and between the sampling sites were examined by principal component analysis. Metal accumulation was particularly evident in the tissues of the sea star Odontaster validus, the bivalve mollusc Laternula elliptica and in the red alga Phyllophora antarctica. However, metal accumulation was not the same for all the analytes, but, rather, depended on the organism characteristics. In particular, the soft tissues of Odontaster validus were characterized by high concentrations of cadmium, zinc and copper, those of Phyllophora antarctica by high concentrations of manganese and nickel, and the tissues of Laternula elliptica by high concentrations of all measured elements, particularly in its digestive gland. The Antarctic data as well as those reported for other pristine coastal ecosystems showed remarkably high natural variability in metal content, which must be taken into account when interpreting results from biomonitoring programmes.

Arsenobetaine is a significant arsenical constituent of the red Antarctic alga Phyllophora antarctica

Environmental context. Although arsenic occurs in marine animals at high concentrations, the pathways by which it is biotransformed and accumulated remain largely unknown. The observation that some species of algae can contain significant concentrations of arsenobetaine, a major marine arsenic species, is relevant to explanations of the source of this compound to marine animals and its transport through the marine food web. Abstract. Significant amounts of arsenobetaine (up to 0.80 μg As g–1 dry mass, representing 17% of the extractable arsenic) were found in the extracts of all four samples of the red alga Phyllophora antarctica collected from two sites in Antarctica (Terra Nova Bay and Cape Evans). The assignment was made with high performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC-ICPMS) based on exact cochromatography with a standard compound with two chromatographic systems (cation-exchange and ion-pairing reversed-phase), each run under two sets of mobile phase conditions. Particular care was taken during sample preparation to ensure that the arsenobetaine was of algal origin and did not result from epiphytes associated with the alga. Another red alga, Iridaea cordata, collected from Terra Nova Bay, did not contain detectable concentrations of arsenobetaine. For both algal species, the majority of the extractable arsenic was present as arsenosugars. Confirmation that marine algae can contain significant amounts of arsenobetaine allows a simpler explanation for the widespread occurrence of this arsenical in marine animals.

Heavy Metals Distribution in Suspended Particulate Matter and Sediment Collected from Vlora Bay (Albania): A Methodological Approach for Metal Pollution Evaluation

Abstract Heavy metals (Al, Fe, As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn) content was evaluated in suspended particulate matter and sediment samples collected from Vlora Bay (Albania) in the framework of Centro Internazionale di Scienze del Mare (CISM) Project activities. The trend of the metals (in general, overlapping that showed by the suspended particulate matter distribution), together with the linear correlation values found between metals, suggested the pivotal role of the Vjosa River and of the inner circulation scheme of Vlora Bay on their distribution. The geoaccumulation index, Igeo, was calculated as a criterion to assess if a metal concentration found in the sediment represents contamination level or can be considered as background level. The results show that metals concentrations in sediments can be considered near the background levels found in the Mediterranean Sea, even if some accumulation was found in several stations. The data were compared to Sediment Quality Guidelines considering the ERL (effects range low) and ERM (effects range medium) values, to evaluate the potential effects of sediment-associated metals on aquatic organisms. The Ni value for all samples was above the ERM value, while Cr and As values were in between ERL and ERM. Metal speciation was also evaluated in some sediment samples. Generally, the metals found were associated with the refractory phases, which constitute up to 80% of the total concentration. Moreover, the sampling strategies and the adopted analytical methods were compared to those recommended by national and international regulations.

Arsenic speciation in marine organisms from Antarctic coastal environments

Environmental context. In studies on trace element accumulation and transformation, it is difficult to distinguish the relative contribution of natural and anthropogenic sources. Antarctic ecosystems provide the opportunity to investigate the natural cycles of the elements, because the food webs are relatively simple and trace element contamination from anthropogenic sources is negligible. We report the arsenic species in various tissues from a range of Antarctic organisms, and compare the patterns of arsenicals with those from similar studies in temperate and tropical waters. Abstract. Antarctic coastal environments offer the unique opportunity to study elemental cycling under pristine conditions. We report arsenic species in various tissues from a range of Antarctic organisms collected from coastal environments, and compare our results with those from similar studies in temperate and tropical waters. The arsenic species were determined in aqueous methanol extracts of tissues (including muscle, liver, gonads and spleen) by HPLC/ICPMS. The major compounds were arsenobetaine and oxo-arsenosugars, with their relative proportions depending on the position of the organism in the food chain and, for some species, on the type of tissue analysed. Several minor compounds, such as dimethylarsinate, trimethylarsine oxide, trimethylarsoniopropionate and arsenocholine were also found; the concentrations of these arsenic species were significantly lower in muscle compared with the other tissues. The transfer of the arsenic through the Antarctic marine food web and the speciation patterns found in the organisms were similar to those reported for comparable organisms from other marine ecosystems. Our study supports the view that the high levels of arsenic occurring in various forms in marine samples is a natural phenomenon, and is little influenced by anthropogenic activities.

Study of the absence of recondensation with low liquid delivery rates by using a cavity sheathing gas in inductively coupled plasma-atomic emission spectrometry

In order to elucidate the absence of recondensation when using very low liquid delivery rates, the effect of flow rate of a sheathing gas injected in a single-pass spray chamber placed before the torch (i.e., cavity chamber) of an inductively coupled plasma atomic emission spectrometer (ICP-AES) on analytical performance and aerosol characteristics using analytical figures of merit was studied. Five different cavities of the so-called torch integrated sample introduction system (TISIS) were evaluated. Furthermore, two nebulizers were used: a PFA micronebulizer and a high efficiency nebulizer (HEN). A low inner volume cyclonic spray chamber (Cinnabar) was taken as the reference system. The studies were performed in terms of sensitivities, limits of detection and extent of the matrix effects and the elements evaluated were Al, As, Ba, Bi, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Sb, Se, Sr, V and Zn. The results indicated that the sheathing gas effect was dependent on the cavity inner volume as well as on the delivery liquid flow rate. For low liquid flow rates (i.e., 28 and 40 μl min−1) and long cavities, the increase in the sheathing gas flow rate caused an initial increase in the ICP-AES sensitivity and, then, a decrease. At higher liquid flow rates (i.e., 80 and 120 μl min−1) and for short spray chambers, an increase in the sheathing gas flow rate led to a decrease in the signal. These trends were explained in terms of the increased primary aerosol mean size (with Sauter mean diameters going from 8.2 to 17.0 μm as the nebulizer gas flow rate decreased from 0.8 to 0.2 l min−1) and reduced droplet inertial losses. The data obtained for the two nebulizers demonstrated that for the HEN, the effect of the sheathing gas was less significant than for the PFA. The TISIS cavities compared favourably with respect to the Cinnabar in terms of sensitivities. Long cavities gave rise to sensitivities up to 2.5 times higher than the Cinnabar. Matrix effects caused by inorganic (nitric acid) as well as organic (ethanol) concomitants were less pronounced for long than for short cavities for all the elements tested. The sheathing gas flow rate did not have a marked effect on the extent of the interferences.