Marilena D'Amato

Changes in Selenium Speciation Associated with Increasing Tissue Concentrations of Selenium in Wheat Grain

Wheat (Triticum aestivum) collected in the Nawanshahr-Hoshiarpur Region (Punjab, India) showed the highest selenium concentrations ever recorded in cereal grains (29-185 microg g(-1)). There was a strong positive relationship between the selenium content in shoots and that in kernels, showing that grain selenium concentration can be predicted from that in the vegetative tissues of the plant. The identity and content of the selenocompounds in the grain samples and in wheat-based reference materials were investigated by HPLC-ICP-dynamic reaction cell-MS. Reversed-phase, cation exchange, and anion exchange HPLC were used to separate the selenium species after ultrasound-assisted enzymatic extraction with an ultrasonic probe. Selenomethionine and selenate accounted for 72-85% and 2-6% of the sum of the selenium species, respectively. The proportion of organic Se species varied with increasing Se content; namely, SeMet showed a relative reduction whereas the other organoselenium compounds increased up to 18-22% of the total chromatographed selenium. Se-methyl-selenocysteine was detected as a minor compound (0.2-0.5%) in high-Se wheat by both reversed-phase and cation exchange HPLC using retention time matching with the standard substance spiked to the sample extracts. Regular consumption of locally produced wheat-based food items may lead the population of the study area to an excessive intake of selenium. On the other hand, the large predominance of selenomethionine shows that local wheat can be a promising raw material for naturally enriched products to be used to supplement human and animal diets in low selenium areas.

Arsenic speciation in wheat and wheat products using ultrasound- and microwave-assisted extraction and anion exchange chromatography-inductively coupled plasma mass spectrometry

Wheat appears to be the major contributor to the intake of inorganic arsenic in countries where the diet is not rice-based. Ultrasound- and microwave-assisted extraction of arsenic in wheat and wheat based food using different solvents or enzymes was investigated in terms of extraction yield and species stability. Four extraction procedures were selected for the study of arsenic speciation in wheat and wheat products by anion exchange HPLC-ICP-MS using a PRP-X100 column with 10 mM NH4H2PO4, 10 mM NH4NO3, and 2% CH3OH at pH 5.5 as the mobile phase. Total arsenic in the samples ranged from 8.6 to 29.8 ng g−1 dry weight. About 95% of the arsenic was found to be present in inorganic form with AsIII as the most abundant species, whereas the remainder was mainly DMA. Microwave-assisted extraction with HNO3 was the most effective in liberating the arsenic species, which were then satisfactorily recovered from the chromatographic column. The LODs achieved, i.e., 0.35–0.46 ng g−1 dry weight, were suitable for the determination of arsenic species at the low levels found in sample extracts.

Arsenic contamination of the environment-food chain: a survey on wheat as a test plant to investigate phytoavailable arsenic in Italian agricultural soils and as a source of inorganic arsenic in the diet.

Seven hundred and twenty-six samples of wheat grains from the majority of Italian agricultural areas were pooled into 141 composite samples, homogeneous with respect to geographical origin and wheat variety. The average arsenic concentration of the pooled samples was 9 ng g(-1), with a range of 2-55 ng g(-1) (dry weight basis). The spread of arsenic concentrations (coefficient of variation of 91%) was related to spatial variability associated with geochemical and environmental factors. Temporal variability was investigated by a 3-year longitudinal study on 7 wheat cultivars grown in 22 areas of central and northern Italy. Average year-to-year variation in arsenic levels was low, and the average of the coefficients of variation was 23%. These results show that mapping of phytoavailable arsenic in agricultural soils can be done by measuring arsenic concentration in representative samples of wheat grains. Arsenic speciation in the grain showed that As(III) and As(V) were the major As compounds, highlighting the importance of wheat as a source of inorganic arsenic in the diet.

Investigating agglomeration and dissolution of silica nanoparticles in aqueous suspensions by dynamic reaction cell inductively coupled plasma-mass spectrometry in time resolved mode

Dynamic reaction cell inductively coupled plasma-mass spectrometry was used to investigate the behaviour of aqueous suspensions of SiO2 nanoparticles in terms of agglomeration and dissolution, two critical aspects in the evaluation of the potential toxicity of nanomaterials in vitro and in vivo. Polyatomic interferences arising from 12C16O and 14N2 on 28Si were dealt with using methane as reactive gas in the dynamic reaction cell. The agglomeration of four different SiO2 nanomaterials at mass concentrations in the range of 40–400 ng ml−1 was studied by time resolved analysis. The intensities of the transient signals generated by the ionisation of a number of nanoparticles at each given sampling time were recorded in time scan and converted into averaged particle diameters using the reference material ERM-FD 100 as a calibrant. The different agglomeration behaviours exhibited by the various nanomaterials were confirmed by experiments using membrane filtration with selected cut-offs. These experiments also revealed that the nanomaterials showed a 30-fold difference in terms of solubility. Electron microscopy (SEM and TEM), used as the reference technique for measurement of primary particle size and particle size distribution, yielded consistent results highlighting the viability of the analytical approach developed. The method allows for rapid screening of the stability of nanosilica suspensions and monitoring of any changes over time with minimal sample preparation.

Dietary exposure to trace elements and radionuclides: the methodology of the Italian total diet study 2012-2014

This article presents the methodology of the Italian Total Diet Study 2012-2014 aimed at assessing the dietary exposure of the general Italian population to selected nonessential trace elements (Al, inorganic As, Cd, Pb, methyl-Hg, inorganic Hg, U) and radionuclides (40K, 134Cs, 137Cs, 90Sr). The establishment of the TDS food list, the design of the sampling plan, and details about the collection of food samples, their standardized culinary treatment, pooling into analytical samples and subsequent sample treatment are described. Analytical techniques and quality assurance are discussed, with emphasis on the need for speciation data and for minimizing the percentage of left-censored data so as to reduce uncertainties in exposure assessment. Finally the methodology for estimating the exposure of the general population and of population subgroups according to age (children, teenagers, adults, and the elderly) and gender, both at the national level and for each of the four main geographical areas of Italy, is presented.

Dietary exposure of the Italian population to inorganic arsenic: The 2012–2014 Total Diet Study

Dietary exposure of the Italian population to inorganic arsenic has been assessed in the national Total Diet Study (TDS) carried out in 2012-2014. Within the TDS, food samples (>3000) were collected to be representative of the whole diet of the population, prepared as consumed, and pooled into 51 food groups, thus modelling the Italian diet. Inorganic arsenic was determined by HPLC-ICP-MS after chemical extraction and quantified in all samples. Occurrence data were combined with national individual consumption data to estimate mean and high level dietary exposure of the general population and of population subgroups according to age and gender, both at the national level and for each of the four main geographical areas of Italy. The intakes assessed are in the lower range of iAs exposure estimates in other European countries carried out without the support of the TDS approach. However, taking the lower limit of the BMDL01 range established by the EFSA as reference point, the margins of exposure are <2 for the mean intake in infants and toddlers and <1 for the 95th percentile intakes in all younger age groups. Our results indicate the goal to check and further reduce the dietary exposure to inorganic arsenic.