1,721,031 research outputs found
Using stable isotope databases for authenticity assessment of commercial flavoured products
No full textDevelopment of honey, vegetable oil, flour, and collagen stable isotope reference materials
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Compound-specific carbon and hydrogen isotope analysis of volatile organic compounds using headspace solid-phase microextraction
No full textNatural flavouring materials are in high demand, and a premium price is paid for all-natural flavourings, making them vulnerable to fraud. At present, compound-specific isotope analysis (CSIA) is perhaps the most sophisticated tool for determining flavour authenticity. Despite promising results, the method is not widely used, and the results are limited to the most common volatile organic compounds (VOCs). This paper describes a robust protocol for on-line measurements of δ13C and δ2H using HS-SPME coupled with GC-C-IRMS and GC-HTC-IRMS for common fruit VOCs. To achieve reproducible and accurate results, a combination of a peak size/linearity correction with drift correction were used. Finally, the results were normalised by multiple point linear regression using the known and measured values of reference materials. Special care was taken to avoid irreproducible isotopic fractionation and the effects of equilibration, adsorption, desorption times and temperatures on δ13C or δ2H values were examined. Method validation was performed, and the average combined measurement uncertainty (MU) was 0.42‰. All the δ13CVPDB values were below ±3*MU, regardless of analytical conditions. In contrast, for δ2HVSMOW-SLAP values, only low temperature (30 °C) with equilibration time (15 min) and shorter adsorption time (between 10 and 20 min) can produce an isotopic difference of <10‰. Therefore, method optimisation can minimise MU, and data normalisation and method validation are essential for obtaining meaningful data for use in flavour authenticity studie
Characterization of truffles (Tuber sp.) in Slovenia using stable isotope approach and elemental composition
No full textAnthropogenic markers in the Holocene stratigraphic sequence of the Gulf of Trieste (northern Adriatic Sea).
No full textThe Gulf of Trieste is a shallow semi-enclosed marine basin in the northernmost part of the Adriatic Sea that has been affected by the relative rise in sea-level during the Holocene. The sedimentary sequences in three cores, ranging in length from 130 to 320 cm, were investigated through the variability in grain-size parameters, major (Al, Fe, S, N, Ca and Mg) and trace (Ti, Mn, Cr,
Ni, Cu, Zn and Hg) elements, organic and inorganic C, δ13C and 14C dating in order to obtain information on paleoenvironmental
evolution and the historical development of heavy metal contamination. The potential sources of pollution are: urban sewage from nearly 400,000 inhabitants, industrial effluents, and 500 yr of Hg mining activity in the Idrija region (western Slovenia), located in the upper basin of the Isonzo river, the main freshwater input to the coastal zone. The conventional 14C ages of bulk sedimentary OC in the basal part of the three cores were 9030±70 (GT1), 8270±50 (GT2) and 9160±120 (GT3) yr BP. An upward increase in highly negative δ13Corg values from the core bottoms indicates that lacustrine-swamp conditions in the study area were rapidly followed by a typical marine depositional environment. Cluster analysis performed on the geochemical data for all subsamples of the three cores identifies several groups with a clear stratigraphic meaning. Factor analysis of the data shows related element groups that can be interpreted as being related to, for instance, the natural contribution from aluminosilicates and carbonates, from organic matter (peat) and the more recent anthropogenic “impact”. Predicted natural linear relationships for metal-Al were obtained from the core subsamples and they can be used as a baseline to evaluate metal enrichments on a regional scale. Results show that more recent sediments in the central sector of the Gulf of Trieste are slightly enriched in Cu (max Enrichment Factor EF=2.1) and Zn (max EF=1.6), and noticeably contaminated by Hg (up to 23.32 μg g−1) to a maximum depth of 90 cm and up to 60 times above the estimated regional background (0.13 μg g−1). The Hg historical trend is well correlated with extraction activity at the Idrija mine, thus allowing indicative sedimentation rate estimation and tentative assessment of the rate of Hg accumulation in bottom
sediments (from 1.77 to 31.49 mg m−2 yr−1 at the surface). The large inventory of Hg in the core GT2 appeared to be the result of
proximity to the fluvial source, which is still active in supplying Hg to the coastal areas and makes the Gulf of Trieste one of the most Hg contaminated area in the whole Mediterranean basin
Geochemical and sedimentological markers in the Holocene stratigraphic sequence of the Gulf of Trieste.
No full textCarbon and Nitrogen isotope compositions of organic matter in coastal marine sediments (the Gulf of Trieste, N Adriatic Sea): indicators of sources and preservation.
No full textTerrestrial organic carbon (OC) preserved in marine sediments is an important reservoir in the global carbon cycle, but remains poorly constrained. We determined the elemental and C- and N-isotopic compositions of organic material (OM) in surface sediments and sediment cores from the Gulf of Trieste (N Adriatic), an area characterized by relatively high riverine input. This multiple tracer approach permits evaluation of how sensitive each tracer is for constraining the terrestrial component of OM. Using the relevant terrestrial and marine OM nd-members, we estimate that the terrestrial contribution ranges from about 90% at the mouth of the Isonzo River and decreases to V10% in the center of the Gulf. In the southern part of the Gulf, 32–44% of terrestrial OC is contributed from smaller rivers, while the d15N values of OM reflect more effective nutrient utilization. Analyses of different size fractions show that smaller particles are consistently more organic-rich and tend to be transported further from the river mouth, depending on river discharge. In the size fraction 2–16 um, elemental ratios and d13Corg and d15N isotopic signatures are consistent with a sedimentary OM pool dominated by bacterially derived biomass. Radiocarbon analyses of sedimentary OC yield depleted D14C values (-338.7 %o to -429.4%o), indicating a significant fraction of relatively old OC. The natural abundance of 13C and 14C tracers suggests a two-component mixture of ancient and modern C in the sediments down to approximately 60 cm sub-bottom, with an estimated ~45% of sedimentary OC probably being derivedfrom ancient sedimentary OC (kerogen). In addition, there is a significant change in the source of organic material downcore inthese sediments which, along with geological evidence, indicate contributions from freshwater swamps typical of coastal lakeswith intermittent connections to the sea (brackish) prior to ~9000 BP. Depth variations in a core from a salt marsh furtherindicate temporal variability of OM deposition and transformations in a changing brackish-marine environment in the past
Isotope partitioning between cow milk and farm water: A tool for verification of milk provenance
Full text linkRationale: The oxygen and hydrogen isotope compositions of the water component of the milk from nine Italian dairy farms were studied together with the farm water for one year. The aim was to verify the importance of farm water and seasonal temperature variation on milk isotope values and propose mathematical relations as new tools to identify the milk origin. Methods: Milk was centrifuged to separate the solids and then distilled under vacuum to separate water. δ(18O/16O) and δ(2H/1H) analyses of the water molecules were carried out using a water equilibrator online with a mass spectrometer. For oxygen and hydrogen isotope determination, water was equilibrated with pure CO2 for 7.5 h and with pure H2 for 5 h, respectively. The isotope ratio value is indicated with δ (expressed on the VSMOW/SLAP scale) as defined by IUPAC. Results: The average annual isotope value of milk at the different cattle sheds is mostly related to the farm water suggesting that the drinking water is the most important factor influencing the isotopic values of the milk water. The milk/water fractionation factor correlates with the milking time and, thus, the seasonal temperature is best described by a 4th order polynomial regression line. A two-level check model was used to verify the milking provenance. Conclusions: This study shows that it is essential to analyze both milk and farm water to indicate provenance. A two-step verification tool, based on the difference between the measured and calculated δ(18O/16O)M values, and the difference between the calculated and estimated milk-water fractionation factors, allowed the source determination of milk. Both conditions must be met if the milk is considered to be from the Parmigiano-Reggiano production region. Although this approach was developed for this region, it can easily be tested and adapted to other dairy production areas
Sources and contribution of terrestrial organic carbon to surface sediments in the Gulf of Trieste (N Adriatic)
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