Related Areas / Projects:
Project funded: July 2016-July 2018.
Funded by the CRT (Richieste Ordinarie)
Development and application of electrochemical sensors for the quantitative determination of mercury and methylmercury in environmental and food matrices.
(In collaboration with Prof. Valentina Carabelli, the Istituto Zooprofilattico di Torino and the Institute of Metrological Research in Turin).
MEDESP group concluded project (in Italian): Development Of An Optical Sensor For The Determination Of Pharmaceutical Compounds And Of Their Photoreactivity In Aqueous Solution (PHARMASENS) - CONCLUDED
Research activities is mainly focused on the following topics:
Determination of inorganic components in pharmaceutical formulations and food
- Traditional Ayurvedic remedies are easily available nowadays not only in India, their country of origin, but also in Western countries. Some of these products (rasausadhi) contain high concentrations of potentially toxic elements as main or secondary ingredients, in addition to elements essential for human health; for these reasons, it is interesting to determine their elemental composition. We assessed the concentrations of Al, As, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Pb, Si and Zn in several ayurvedic formulations manufactured in various places in India, purchased on the Internet and in Italian pharmacy. Concentrations were determined by inductively coupled plasma-optical emission spectrometry or (for Pb and Cd) by graphite furnace atomic absorption spectrometry after sample mineralization. We compared the calculated daily intake of each element with reference values, considering maximum tolerable intake levels issued by the European Food Safety Authority and by the Joint FAO/WHO Expert Committee on Food Additives or recommended nutrient amounts. The experimental results were treated with chemometric pattern recognition techniques. While elements content in medicines purchased in Italian pharmacy and on the Internet were found largely than the safety limits, the daily intake of As, Hg and Cu upon consumption of some medicines traditionally manufactured in India largely exceeded the tolerable intake level of these elements. We have also determined the bioaccessibility of potentially toxic elements by treating the medicines with extracting solutions simulating the gastric and intestinal fluids.
Some considered Ayurvedic formulations purchased in India
- The concentrations of Cd, Cu and Pb were determined in dandelion, i.e. Taraxacum officinale, leaves and underlying soil samples collected at 12 sites in the Province of Cuneo in the vicinity of streets or roundabouts. Taraxacum officinale leaves are traditionally picked up and eaten as salad, but this plant is able to tolerate a wide range of environmental conditions among which the presence of high concentrations of metals. So the knowledge of the metal content in Taraxacum officinale from the point of view of food safety. The concentrations were compared with reference values for plant and soils and with maximum allowable concentrations in edible vegetables according to WHO. Neither dandelion nor soil samples were found to be polluted by metals, but the comparison with limits for vegetables suggests that caution should be used in consuming spontaneously growing vegetables.
Development of new analytical methods for the determination of trace elements using electrochemical sensors;
- We developed a new procedure for the determination of aqueous Hg(II) by anodic stripping voltammetry at a gold nanoparticle-modified glassy carbon electrode (AuNPs-GCE). The gold nanoparticles were electrodeposited onto a glassy carbon electrode at -0.8 V for 360 s using a solution of HAuCl4. The AuNPs-GCE showed to provide better performances than solid and film gold electrodes, in particular for the lower detection limits and the repeatability. The feasibility of using the AuNPs-GCE to determine Hg in drinking waters, sediments, particulate matter, tuna fish and pharmaceuticals was demonstrated: an excellent agreement was found between the results of the analyses and the expected values.With this technique we also developed a procedure for the determination of methylmercury and for the differentiation between methylmercury and inorganic mercury. The procedure had good accuracy, repeatability and linearity. The determination of total mercury in solutions containing both methylmercury and inorganic mercury was performed after converting the former into the inorganic form. Different sample solution pre-treatments were tested for this purpose, and an acid digestion in a microwave oven with HNO3 and H2O2 was found to be the most effective. The selective determination of methylmercury in the presence of inorganic mercury was possible after masking the latter through reduction to the elemental state with SnCl2. The amount of inorganic mercury was determined by difference.
SEM image of gold nanoparticles electrochemically deposited on glassy carbon electrode
- We evaluated the efficiency of the determination of As(III) by anodic stripping voltammetry (ASV) using a lateral gold electrode. The applicability of the procedure for As(III) determination in drinking waters was demonstrated. Furthermore, we studied the modifications of the electrode surface during use. Cyclic voltammetry (CV) was used to study the electrochemical behaviour of As(III) and for the daily monitoring of electrode surface. We evaluated the possibility to apply the equations valid for flow systems also to a stirred system, in order to calculate the number of electrons transferred per molecule during the stripping step.
Development of new remediation procedures for contaminated soils
- We have investigated the possibility to apply natural clays (montmorillonite and vermiculite) for the clean-up of extracts resulting from the application of soil washing to a metal-contaminated soil collected from an industrial site (ACNA) in Cengio, Italy, included in the Italian list of national priorities for environmental reclamation. The soil was initially characterized for its total metal content; we also studied the availability of the pollutants by leaching at pH 5.0 and by Tessier's sequential extraction procedure. The fractionation and speciation of As in a contaminated soil were investigated, and a remediation strategy was developed. By applying a speciation procedure we found that As(V) prevails over As(III) whereas more than 40 % of total arsenic is in organic form. The fractionation of As was investigated with a sequential extraction methods designed for anions. The possibility of recovering the metals by elution with acid and of reusing the clay was also demonstrated.
Study of the interaction between trace metals and clays and between trace metals and plants;
- We evaluated the distribution of 15 metal ions, namely Al, Cd, Cu, Cr, Fe, La, Mn, Ni, Pb, Sc, Ti, V, Y, Zn and Zr, in the soil of a contaminated site in Piedmont. This area was found to be heavily contaminated by Cu, Cr and Ni. The availability of these metal ions was studied using Tessier’s sequential extraction procedure: the fraction of mobile species, which potentially is the most harmful for the environment, was much higher than that normally present in unpolluted soils. This soil was hence used to evaluate the effectiveness of treatment with vermiculite to reduce the availability of the pollutants to two plants, Lactuca sativa and Spinacia oleracea, by pot experiments. The addition of vermiculite significantly reduced the uptake of metal pollutants by plants, confirming the possibility of using this clay in amendment treatments of metal-contaminated soils. The effect of plant growth on metal fractionation in soils was investigated. The sum of the metal percentages extracted into the first two fractions of Tessier’s protocol was found to be suitable in predicting the phytoavailability of most of the pollutants present in the investigated soil.
Study of the behaviour of metals in different natural matrices from contaminated and remote areas
- Antarctica is the most isolated continent on Earth and therefore it is nearly unaffected by anthropogenic activities. For this reason, this continent is considered a unique laboratory for investigating the natural behaviour of organic and inorganic compounds in the environment with a minimum level of anthropogenic influence. We have examined the distribution of a series of elements in lacustrine compartments from Terra Nova Bay, Northern Victoria Land, Antarctica in order to gain insight into the natural processes regulating species distribution in this environmental compartment and to point out the occurrence of possible present or future local and/or global anthropogenic contamination.In order to ascertain the natural dynamics of several elements, namely Al, As, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, Ti and Zn, as well as the possible perturbations by human activities and/or global contamination, soils and sediments from four catchments (Tarn Flat, Edmonson Point, Inexpressible Island and Northern Foothills) were studied. To accomplish the above mentioned objectives, the particle-size distribution and mineralogical composition, as well as the total C, H and N contents and the total concentrations of the investigated elements were determined. Finally in order to assess metal mobility, the modified BCR three-step sequential extraction procedure was applied to the samples and the partitioning of five metals, namely Cr, Fe, Mn, Pb and Zn, into different fractions was determined.Then, our attention was focused on freshwaters, algae, mosses and (for one site) on lichens. Lake water composition was found to be influenced by marine spray, lake geographical position and meltwater input. The bioaccumulation of elements from waters by algae was pointed out. Higher concentrations in algae than in mosses have been interpreted taking into account this phenomenon. Data processing by chemometric techniques showed correlations between elements and similarities among samples. No evidence of a detectable contamination by metals was found in the investigated area.
- The concentrations of 21 elements, namely Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, La, Mg, Mn, Na, Ni, P, Pb, Sr, Ti, V and Zn, were investigated in a marine sediment core from the Ross Sea (Antarctica). The elaboration of the experimental results by chemometric techniques has allowed us to exclude anthropogenic contamination whereas it has suggested a dependence on biological factors, such as the presence of corals. Furthermore, two sequential sequential extraction procedures were applied to selected sediment samples in order to evaluate metal mobility, as well as their availability. This study has shown the importance to combine data from total element concentrations with results from extraction procedures to better understand the environmental matrices.
- The temporal trends of ten elements, namely Cl, Cu, Cr, Fe, Mg, Ni, P, S, Zn and Zr, in airborne particulate matter sampled in the urban area of Turin were determined by wavelength dispersive X-ray fluorescence for the period from 2002 to 2005. A clear seasonal pattern with higher concentrations of most of the elements in the cold periods was observed. Moreover, no clear change in the chemical composition of atmospheric particulate matter was evidenced during the sampling period to indicate that similar sources have influenced the elemental composition of it in these last years. The application of multivariate chemometric techniques (Principal Component Analysis and Hierarchical Cluster Analysis) to the experimental results allowed us to identify correlations among the investigated elements and to reveal similarities and differences between sampling sites, highlighting the existence of the following main emitting sources: vehicular traffic/fossil fuel combustion, soil dust, anthropogenic secondary aerosol and NaCl.
Use of chemometric pattern recognition techniques for data processing
- We use of chemometric pattern recognition techniques for data processing. We are authors of two reviews about the role of chemometrics in single and sequential extraction assays.
- National Program for Research in Antarctica (PNRA)
Analytical techniques available to the research team include:
- stripping voltammetry (ASV, CSV, AdSV) with mercury electrodes;
- stripping voltammetry with nanostructured sensors;
- inductively coupled plasma atomic emission spectroscopy (ICP-AES);
- graphite furnace atomic adsorption spectroscopy (GF-AAS);
- inductively coupled plasma mass spectrometry (ICP-MS).
Software for statistics and chemometrics:
- Prof. Murugesan Velayutham (Anna University, Chennay, India);
- Prof. Massimo Gasparon (University of Queensland, St. Lucia, Australia);
- Dr. Tanmoy Karak, Tea Research Association, Kolkata, India.