No abstract

Edible seaweed consumption is a route of exposure to arsenic. However, little attention has been paid to estimate the bioaccessibility and/or bioavailability of arsenosugars in edible seaweed and their possible degradation products during gastrointestinal digestion. This work presents first use of combined inductively coupled plasma mass spectroscopy (ICP-MS) with electrospray ionization tandem mass spectrometry (ESI-MS/MS) with two-dimensional HPLC (size exclusion followed by anion exchange) to compare the qualitative and quantitative arsenosugars speciation of different edible seaweed with that of their bioavailable fraction as obtained using an in vitro gastrointestinal digestion procedure. Optimal extraction conditions for As species from four seaweed namely kombu, wakame, nori and sea lettuce were selected as a compromise between As extraction efficiency and preservation of compound identity. For most investigated samples, the use of ammonium acetate buffer as extractant and 1 h sonication in a water bath followed by HPLC-ICP-MS resulted in 40-61% of the total As to be found in the buffered aqueous extract, of which 86-110% was present as arsenosugars (glycerol sugar, phosphate sugar and sulfonate sugar for wakame and kombu and glycerol sugar and phosphate sugar for nori). The exception was sea lettuce, for which the arsenosugar fraction (glycerol sugar, phosphate sugar) only comprised 44% of the total extracted As. Interestingly, the ratio of arsenobetaine and dimethylarsinic acid to arsenosugars in sea lettuce extracts seemed higher than that for the rest of investigated samples. After in vitro gastrointestinal digestion, approximately 11-16% of the total As in the solid sample was found in the dialyzates with arsenosugars comprising 93-120% and 41% of the dialyzable As fraction for kombu, wakame, nori and sea lettuce, respectively. Moreover, the relative As species distribution in seaweed-buffered extracts and dialyzates was found to be very similar. Collection of specific fractions from the size-exclusion column to be analysed using anion-exchange HPLC-ESI-MS/MS enabled improved chromatographic selectivity, particularly for the less retained arsenosugar (glycerol sugar), facilitating confirmation of the presence of arsenosugars in seaweed extracts and dialyzates. Using this approach, the presence of arsenobetaine in sea lettuce samples was also confirmed.

The effect of added organic acids on the calcium availability of vegetables was investigated using the dialysis profiles obtained from an in vitro simulated gastrointestinal digestion with continuous-flow dialysis method. Citric acid was the most effective enhancer followed by tartaric, malic, and ascorbic acids. For amaranth, which has a low calcium availability (5.4%), a significant increase of availability was observed with increasing concentrations of all acids studied. With the continuous-flow dialysis approach, organic acids could be observed to promote the dialyzability even at an elevated intestinal pH. An enhancement effect from added organic acids was not clearly observed for Chinese kale, which itself contains a high amount of available calcium (52.9%).

The CCQM-K123 key comparison was organized by the Inorganic Analysis Working Group (IAWG) of CCQM to assess and document the capabilities of the national metrology institutes (NMIs) or the designated institutes (DIs) to measure the mass fractions of sodium, calcium, potassium, magnesium phosphorous and sulfur in biodiesel fuel (BDF). National Metrology Institute of Japan (NMIJ) and National Institute of Standards and Technology (NIST) acted as the coordinating laboratories. Results were submitted by 11 NMIs and DIs. Most of the participants used inductively coupled plasma-mass spectrometry (ICP-MS), isotope dilution technique with ICP-MS and inductively coupled plasma-optical emission spectrometry (ICP-OES) with microwave acid digestion. Accounting for relative expanded uncertainty, comparability of measurement results for each of Na, Ca, K, Mg and P was successfully demonstrated by the participants. Concerning S, the variation in results between participants, particularly those using IDMS methods was observed. According to the additional evaluation and investigation, the revised results were overlapping between IDMS measurements at the k = 2 level. However, this KC does not support S measurements. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

The key comparison CCQM-K89 was undertaken to demonstrate the capability of participating NMIs and DIs in measuring the contents of incurred trace elements (total arsenic, cadmium and lead) and essential elements (calcium and zinc) at µg/g (for arsenic, cadmium, lead and zinc) and mg/g (for calcium) levels in a herb matrix sample by various analytical techniques.This key comparison was organized by the Government Laboratory of the Hong Kong Special Administrative Region (GLHK) and agreed at the Inorganic Analysis Working Group Meeting in Hindås, Sweden in October 2010 as a benchmarking exercise with arsenic (a trace element) and calcium (an essential element) chosen as the 'exemplary' elements. It was also agreed that a pilot study CCQM-P126 would be run in parallel with this key comparison.The key comparison serves to facilitate claims by participants on the Calibration and Measurement Capabilities (CMCs) as listed in Appendix C of the Key Comparison Database (KCDB) under the Mutual Recognition Arrangement of the International Committee for Weights and Measures (CIPM MRA).A total of 20 NMIs/DIs registered for this programme and 18 of them submitted their results. Most of the participants used microwave acid digestion methods for sample dissolution. For the instrumental determination, a variety of techniques like ICP-MS, AAS, INAA, ICP-AES were employed by the participants. For this key comparison, inorganic core capabilities have been demonstrated by concerned participants with respect to methods including ICP-MS (without isotope dilution), ID-ICP-MS, ICP-AES, INAA, AAS and ion chromatography with iteratively matrix-matched calibration on the determination of total arsenic, calcium, cadmium, lead and zinc in a matrix of herb.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).