Ana I. Cabañero

Quantification and speciation of mercury and selenium in fish samples of high consumption in Spain and Portugal.

Mercury (Hg) and selenium (Se) determinations were carried out to evaluate human exposure to those elements through fish consumption in Spain and Portugal. Atomic fluorescence spectroscopy (AFS) was applied in a cold vapor mode for total mercury quantification and was also hyphenated to gas chromatography (GC) to achieve the speciation of organomercurial species in fish samples. The results obtained show the highest concentration of Hg in swordfish and tuna (0.47±0.02 and 0.31±0.01 μg g−1, respectively), and a much lower concentration in sardine, mackerel shad, and octopus (0.048±0.002, 0.033±0.001, and 0.024±0.001 μg g−1, respectively), The determination of alkyl mercury compounds revealed that 93–98% of mercury in the fish samples was in the organic form. Methylmercury (MeHg) was the only species found in the three fish species with higher mercury content.Total selenium concentraton was high in sardine, swordfish, and tuna (0.43±0.02, 0.47±0.02, and 0.92±0.01 μg g−1, respectively), but low in mackeral shad and octopus (0.26±0.01 and 0.13±0.01 μg g−1, respectively). Speciation of selenium compounds was done by high-performance liquid chromatography in conjunction with inductively coupled plasma mass spectrometry (LC-ICP-MS). Selenomethionine (SeMet) was the only selenium compound identified in the fish samples with higher selenium content.Among the fish species studied, sardine had the most favourable Se:Hg and SeMet:MeHg molar ratios; therefore, its consumption seems to be preferable.

Isotope ratio mass spectrometry coupled to liquid and gas chromatography for wine ethanol characterization

Two new procedures for wine ethanol 13C/12C isotope ratio determination, using high-performance liquid chromatography and gas chromatography isotope ratio mass spectrometry (HPLC/IRMS and GC/IRMS), have been developed to improve isotopic methods dedicated to the study of wine authenticity. Parameters influencing separation of ethanol from wine matrix such as column, temperature, mobile phase, flow rates and injection mode were investigated. Twenty-three wine samples from various origins were analyzed for validation of the procedures. The analytical precision was better than 0.15 per thousand, and no significant isotopic fractionation was observed employing both separative techniques coupled to IRMS. No significant differences and a very strong correlation (r = 0.99) were observed between the 13C/12C ratios obtained by the official method (elemental analyzer/isotope ratio mass spectrometry) and the proposed new methodology. The potential advantages of the developed methods over the traditional one are speed (reducing time required from hours to minutes) and simplicity. In addition, these are the first isotopic methods that allow 13C/12C determination directly from a liquid sample with no previous ethanol isolation, overcoming technical difficulties associated with sample treatment.

Simultaneous Stable Carbon Isotopic Analysis of Wine Glycerol and Ethanol by Liquid Chromatography Coupled to Isotope Ratio Mass Spectrometry

A novel procedure was established for the simultaneous characterization of wine glycerol and ethanol (13)C/(12)C isotope ratio, using liquid chromatography/isotope ratio mass spectrometry (LC-IRMS). Several parameters influencing separation of glycerol and ethanol from wine matrix were optimized. Results obtained for 35 Spanish samples exposed no significant differences and very strong correlations (r = 0.99) between the glycerol (13)C/(12)C ratios obtained by an alternative method (gas chromatography/isotope ratio mass spectrometry) and the proposed new methodology, and between the ethanol (13)C/(12)C ratios obtained by the official method (elemental analyzer/isotope ratio mass spectrometry) and the proposed new methodology. The accuracy of the proposed method varied from 0.01 to 0.19 per thousand, and the analytical precision was better than 0.25 per thousand. The new developed LC-IRMS method it is the first isotopic method that allows (13)C/(12)C determination of both analytes in the same run directly from a liquid sample with no previous glycerol or ethanol isolation, overcoming technical difficulties associated with complex sample treatment and improving in terms of simplicity and speed.

Study of mercury–selenium interaction in chicken liver by size exclusion chromatography inductively coupled plasma mass spectrometry

In order to estimate metal distribution patterns in biomolecules of different sizes and their possible modification after long-term Hg and Se exposition, multi-elemental distribution of the cytosols of chicken livers were evaluated. For this purpose 72 chickens were fed under different controlled conditions. Chickens were exposed to Hg(II) and MeHg added to feed with or without selenium supplementation. Size-exclusion chromatography with ICP-MS detection was developed for multielemental (S, P, Cu, Zn, Se, Mn, Fe and Hg) speciation in chicken liver cytosol and optimisation of the separation parameters (25 mM Tris-HCl buffer, 50 mM KCl, pH 6.8, 1 ml min−1) was carried out. The liver extracts were injected into the column four times each and the variation between the runs was small (RSD 300–45 kDa), whereas Mn is mainly associated to high (116 kDa) and low (0.03 kDa) molecular weight species and P is mainly associated to low molecular weight species (5.5 kDa). Changes in the subcellular distribution and distribution patters caused by long-term Hg–Se administration have been discussed.

Carbon isotopic characterization of cider CO2 by isotope ratio mass spectrometry: a tool for quality and authenticity assessment

RATIONALE The cider market is an important sector of the food industry in certain regions. Adulteration of cider can happen in several ways: for example, by the addition of sugar, or of exogenous CO(2) to certain types of cider. Because such practices are not allowed by either Spanish legislation or the legislation of other countries, it is essential to study possible methods to detect these unauthorized practices. For this purpose a procedure was required to study the stable carbon isotopic composition of CO(2) in cider. METHODS A liquid sample of cider was transferred to a vial and CO(2) from the headspace of the vial was analyzed using a peripheral device interfaced to an isotope ratio mass spectrometer. Separation of the CO(2) from water and ethanol was achieved using a gas chromatography column located in the peripheral device. RESULTS The values for repeatability and reproducibility obtained indicated the robustness of the method, which is required for routine analysis. Ninety cider samples from various origins were analyzed, most of which showed a (13)C content consistent with the declared origin. The δ(13)C ranged from -24.80‰ to -20.89‰ for ciders with endogenous carbon dioxide (-22.74 ± 0.79‰) and -37.13‰ to -26.00‰ if industrial CO(2) was added. Several samples were also suspected of C4 sugar addition prior to the fermentation. CONCLUSIONS A fast, accurate and simple method for cider adulteration detection was developed. The addition of exogenous CO(2) as well as C4 sugar addition prior to fermentation could be detected. The method showed advantages over existing methods in term of simplicity (no sample preparation and very long-term stability of the sample), speed (less than 10 min/sample) and precision ((r ≤0.32 and R ≤0.42).