Iodine concentration of milk-alternative drinks available in the UK in comparison with cows' milk.

Iodine deficiency is present in certain groups of the UK population, notably in pregnant women; this is of concern as iodine is required for fetal brain development. UK milk is rich in iodine and is the principal dietary iodine source. UK sales of milk-alternative drinks are increasing but data are lacking on their iodine content. As consumers may replace iodine-rich milk with milk-alternative drinks, we aimed to measure the iodine concentration of those available in the UK. Using inductively coupled plasma-MS, we determined the iodine concentration of seven types of milk-alternative drink (soya, almond, coconut, oat, rice, hazelnut and hemp) by analysing forty-seven products purchased in November/December 2015. For comparison, winter samples of conventional (n 5) and organic (n 5) cows' milk were included. The median iodine concentration of all of the unfortified milk-alternative drinks (n 44) was low, at 7·3 µg/kg, just 1·7 % of our value for winter conventional cows' milk (median 438 µg/kg). One brand (not the market leader), fortified its soya, oat and rice drinks with iodine and those drinks had a higher iodine concentration than unfortified drinks, at 280, 287 and 266 µg/kg, respectively. The iodine concentration of organic milk (median 324 µg/kg) was lower than that of conventional milk. Although many milk-alternative drinks are fortified with Ca, at the time of this study, just three of forty-seven drinks were fortified with iodine. Individuals who consume milk-alternative drinks that are not fortified with iodine in place of cows' milk may be at risk of iodine deficiency unless they consume alternative dietary iodine sources.

The potential of bioprinting for preparation of nanoparticle-based calibration standards for LA-ICP-ToF-MS quantitative imaging.

This paper discusses the feasibility of a novel strategy based on the combination of bioprinting nano-doping technology and laser ablation-inductively coupled plasma time-of-flight mass spectrometry analysis for the preparation and characterization of gelatin-based multi-element calibration standards suitable for quantitative imaging. To achieve this, lanthanide up-conversion nanoparticles were added to a gelatin matrix to produce the bioprinted calibration standards. The features of this bioprinting approach were compared with manual cryosectioning standard preparation, in terms of throughput, between batch repeatability and elemental signal homogeneity at 5 µm spatial resolution. By using bioprinting, the between batch variability for three independent standards of the same concentration of 89Y (range 0-600 mg/kg) was reduced to 5% compared to up to 27% for cryosectioning. On this basis, the relative standard deviation (RSD) obtained between three independent calibration slopes measured within 1 day also reduced from 16% (using cryosectioning) to 5% (using bioprinting), supporting the use of a single standard preparation replicate for each of the concentrations to achieve good calibration performance using bioprinting. This helped reduce the analysis time by approximately 3-fold. With cryosectioning each standard was prepared and sectioned individually, whereas using bio-printing it was possible to have up to six different standards printed simultaneously, reducing the preparation time from approximately 2 h to under 20 min (by approximately 6-fold). The bio-printed calibration standards were found stable for a period of 2 months when stored at ambient temperature and in the dark.

Versailles project on advanced materials and standards (VAMAS) interlaboratory study on measuring the number concentration of colloidal gold nanoparticles.

We describe the outcome of a large international interlaboratory study of the measurement of particle number concentration of colloidal nanoparticles, project 10 of the technical working area 34, "Nanoparticle Populations" of the Versailles Project on Advanced Materials and Standards (VAMAS). A total of 50 laboratories delivered results for the number concentration of 30 nm gold colloidal nanoparticles measured using particle tracking analysis (PTA), single particle inductively coupled plasma mass spectrometry (spICP-MS), ultraviolet-visible (UV-Vis) light spectroscopy, centrifugal liquid sedimentation (CLS) and small angle X-ray scattering (SAXS). The study provides quantitative data to evaluate the repeatability of these methods and their reproducibility in the measurement of number concentration of model nanoparticle systems following a common measurement protocol. We find that the population-averaging methods of SAXS, CLS and UV-Vis have high measurement repeatability and reproducibility, with between-labs variability of 2.6%, 11% and 1.4% respectively. However, results may be significantly biased for reasons including inaccurate material properties whose values are used to compute the number concentration. Particle-counting method results are less reproducibile than population-averaging methods, with measured between-labs variability of 68% and 46% for PTA and spICP-MS respectively. This study provides the stakeholder community with important comparative data to underpin measurement reproducibility and method validation for number concentration of nanoparticles.

Cytosolic distribution of Cd, Cu and Zn, and metallothionein levels in relation to physiological changes in gibel carp (Carassius auratus gibelio) from metal-impacted habitats.

In the present study the impact of environmental metal contamination in gibel carp (Carassius auratus gibelio) was investigated coupling disturbances in subcellular metal distribution to effect biomarkers. Gibel carp were caught at six different sampling sites in Flanders (Belgium), characterized by different degrees in environmental metal contamination. Tissue Cd, Cu and Zn concentrations and total metallothioneon (MT) levels were determined in gills, liver and kidney. Cytosolic metal distribution was measured in the main accumulating organs, liver and kidney, revealing tissue- and metal-dependent profiles. The MT pool dominated the cytosolic distribution profile. Although the importance of the MT pool increased with increasing environmental and cytosolic metal concentrations, also an undefined fraction of Cu and Cd fractions (probably free metal ions or metals bound to small organic complexes) increased at the most contaminated sampling sites. Disturbances in serum ion concentrations, serum alanine aminotransferase activity (ALT), hematocrite and condition factor were measured, as indicators of toxic effects. At the sampling site with the highest environmental Cd pollution a significant decrease in serum Ca(2+) concentrations and a significantly increased serum ALT activity were measured suggesting incomplete detoxification of Cd. Increased serum ALT concentrations suggested structural liver damage. The fact that the liver tissue, and probably also the kidney, could not cope with this high Cd burden in combination with the increased uptake of dissolved Cd through the gills most probably contributed to the perturbed serum Ca(2+) homeostasis.

Food-chain selenium and human health: spotlight on speciation.

There is a growing appreciation that it is not just the total intake of dietary Se that is important to health but that the species of Se ingested may also be important. The present review attempts to catalogue what is known about Se species in foods and supplements and the health effects in which they are implicated. The biosynthetic pathways involved in Se assimilation by plants and the way in which Se species are metabolised in animals are presented in order to give an insight into the species likely to be present in plant and animal foods. Known data on the species of Se in the food chain and in food supplements are tabulated along with their concentrations and the analytical methodology used. The latter is important, since identification that is only based on retention-time matching with authentic standards must be considered as tentative: for evidence of structural confirmation, fragmentation of the molecular ion in addition to MS data is required. Bioavailability, as normally defined, is higher for organic Se species. Health effects, both beneficial and toxic, thought to be associated with specific Se species are described. Potent anti-tumour effects have been attributed to the low-molecular-weight species, Se-methyl-selenocysteine and its gamma-glutamyl-derivative, found in a number of edible plants of the Allium and Brassica families. There remain considerable gaps in our knowledge of the forms of Se that naturally occur in foods. Without adequate knowledge of Se speciation, false conclusions may be drawn when assessing Se requirements for optimal health.

Induction and metal speciation of metallothionein in wood mice (Apodemus sylvaticus) along a metal pollution gradient.

We investigated the binding of Cd, Cu, and Zn to metallothionein (MT) and other metal-binding proteins in free-living wood mice (Apodemus sylvaticus L.) captured in four areas along a metal pollution gradient. We measured total and cytosolic Cd, Cu, and Zn concentrations in mouse liver and kidney by means of inductively coupled plasma-mass spectrometry (ICP-MS). Total (Cu, Cd, Zn)-MT levels were determined in the same tissues by means of the cadmium thiomolybdate saturation assay. Metal speciation of metalloproteins was studied by means of size-exclusion high-performance liquid chromatography-ICP-MS. Liver and kidney of wood mice from the site adjacent to the pollution source showed the highest Cd and Zn concentrations (total and cytosolic) and (Cu, Cd, Zn)-MT levels compared to the other sites farther away from the pollution source. No or only small site differences in tissue Cu concentrations were observed. Almost all the variation (85-95%) in hepatic and renal (Cu, Cd, Zn)-MT levels was explained by the total or cytosolic hepatic Zn and Cd concentration or the renal Cd concentration, respectively. An analysis of the cytosolic metal speciation showed that the Cd-MT, Cu-MT, and Zn-MT fractions in liver and kidney increased significantly with increasing cytosolic metal concentrations. Metals associated with the other cytosolic protein fractions did not increase with increasing exposure. These results illustrate the important role of MT in metal homeostasis and detoxification processes. We conclude that MT is a useful biomarker for environmental metal contamination in free-living wood mice.

Anion-exchange high performance liquid chromatography hyphenated to inductively coupled plasma-isotope dilution-time-of-flight mass spectrometry for speciation analysis of metal complexes with metallothionein isoforms in gibel carp (Carassius auratus gibelio) exposed to environmental metal pollution.

The capability of post-column isotope dilution (ID) combined with anion-exchange HPLC-ICP-time-of-flight (TOF)-MS was for the first time investigated for environmental quality assessment through metal speciation analysis of metallothionein (MT) isoforms in cytosols of gibel carp (Carassius auratus gibelio), used as biomarkers for environmental metal exposure. A full spectral scanning of the biological sample (with 50 microl injection volume) using ICP-TOF-MS in transient mode allowed fast multi-isotope screening of cytosolic metal-containing fractions and to investigate the presence of matrix-induced interferences. The MT cytosolic fraction of liver and kidney of the carp, sampled at three different sampling sites in Belgium, was partially purified using size-exclusion (SE) HPLC. Quantification of the elements Cd (toxic) and Zn and Cu (essential) associated with MT isoforms in this fraction was addressed using an hybrid approach based on post-column addition of the enriched isotopes 65Cu, 67Zn, 106Cd and monitoring on-line the isotope ratios 63Cu/65Cu, 64Zn/67Zn and 114Cd/106Cd by ICP-MS with a time of flight instrument, which was coupled to anion-exchange HPLC. With this separation method, baseline separation of up to five MT isoforms, which is required for quantitative metal speciation by HPLC-ICP-IDMS, was achieved within a run of 15 min. The MT fraction of the cytosols was also analysed for the total metal content using IDMS with size-exclusion HPLC-ICP-MS and species-unspecific calibration. Results showed significant differences between speciation results and total MT concentrations of control fish and fish from the most contaminated sampling sites, revealing the potential of gibel carp MT for sequestering excess intracellular free-ions (essential and toxic elements) and for its protection against metal toxicity. Preferences for metal sequestration of metal complexes with MT isoforms were also found to be tissue-specific: excess of Cd was found preferably bound to a major MT isoform (tR = 8.0 min) in kidney, whereas excess intracellular Zn appeared to be mostly sequestered by four MT isoforms (tR=7.3, 8.0, 12.2 and 14.4 min) in liver, the MT form with tR = 8.0 min being the main Zn scavenger form. Such kind of quantitative speciation information on the preferences of MT isoforms in different fish organs for sequestering heavy metals, reported here for the first time, is important to elucidate the role of isoform-specific induction of vertebrate fish MT in metal detoxification and the use of MT as biomarker.

Induction and binding of Cd, Cu, and Zn to metallothionein in carp (Cyprinus carpio) using HPLC-ICP-TOFMS.

The binding of Cd, Cu, and Zn to metallothionein in carp was studied under control and acute Cd exposure scenarios. Carp were exposed to different Cd concentrations for 96 h. Total (Cu, Cd, Zn)-MT levels were determined by the cadmium thiomolybdate saturation assay. Total tissue and cytosolic Cd, Cu, and Zn concentrations were determined by ICP-MS. The cytosolic metal speciation was determined by high pressure liquid chromatography (size-exclusion [SE] in combination with anion exchange [AE]) directly coupled to an inductively coupled plasma time of flight mass spectrometer (ICP-TOFMS). This coupled technique allows the chromatographic separation and online determination of the metals associated to the protein fractions separated. Very strong differences in the tissue compartmentalization and cytosolic speciation of the metals were observed. For example, over 30% of cytosolic zinc was bound to MT in liver while this was only 2% in the kidneys although total cytosolic levels were considerably higher. Induction of metallothionein during cadmium exposure was also tissue specific, displaying different response patterns in gills, liver, and kidney. Cadmium accumulated much stronger in liver and kidney compared to the gills and the latter also showed much lower MT levels. The renal MT-induction was more sensitive to Cd exposure than the hepatic MT induction since a significant increase of Cd-MT and total MT levels occurred at lower tissue Cd concentrations in the kidney in comparison to the liver, except for the highest Cd exposure level where a drastic 10-fold increase in hepatic Cd-MT was observed. At this Cd exposure level also an apparent spill over of zinc to the high molecular weight fraction was observed in the kidneys.

Study of the effect of sample preparation and cooking on the selenium speciation of selenized potatoes by HPLC with ICP-MS and electrospray ionization MS/MS.

The efficiency of enzymatic hydrolysis and leaching with water using accelerated solvent extraction (ASE) or boiling was investigated for quantitative Se speciation in selenized potatoes using reversed phase HPLC coupled to ICP-MS. Preliminary identification of selenomethionine (SeMet), Se-methylselenocysteine (SeMeCys), and selenate in extracts of potato skin and flesh was achieved using complementary reversed phase and anion-exchange HPLC-ICP-MS and retention time matching with standards. The quantitative speciation data revealed a higher percentage of selenomethionine (73% of the total Se) found in the flesh in comparison with skin (containing 21% of the total Se as SeMet). ASE and boiling in water were found to be similar in terms of Se extraction efficiency and profiles. However, ASE was found to be more efficient than boiling with respect to sample cleanup and reduced sample handling. The presence of SeMet at parts per billion levels in selenized potatoes was confirmed by reversed phase HPLC with online ESI MS/MS.

Current mass spectrometry strategies for selenium speciation in dietary sources of high-selenium.

This document reviews the most relevant mass spectrometry approaches to selenium (Se) speciation in high-Se food supplements in terms of qualitative and quantitative Se speciation and Se-containing species identification, with special reference to high-Se yeast, garlic, onions and Brazil nuts. Important topics such as complexity of Se speciation in these materials and the importance of combining Se-specific detection and molecule-specific determination of the particular species of this element in parallel with chromatography, to understand their nutritional role and cancer preventive properties are critically discussed throughout. The versatility and potential of mass spectrometric detection in this field are clearly demonstrated. Although great advances have been achieved, further developments are required, especially if "speciated"certified reference materials (CRMs) are to be produced for validation of measurements of target Se-containing species in Se-food supplements.