Methylation and bio-accessibility assessment of arsenate in crickets (Gryllusbimaculatus).

The ability of an organism to biomethylate toxic inorganic arsenic (As) determines both, the amount of As available for uptake higher up the food chain and the toxicity of bioavailable As. An exposure study was conducted to determine ability of farmed crickets to metabolize dietary arsenate. Crickets were exposed to 1.3 ± 0.1, 5.1 ± 2.5 and 36.3 ± 5.6 mg kg-1 dietary arsenate and quantitation of total As showed retention of 0.416 ± 0.003, 1.3 ± 0.04 and 2.46 ± 0.09 mg kg-1, respectively. Speciation analysis revealed that crickets have well developed ability to biomethylate dietary arsenate and the most abundant methylated As compound was DMA followed by MMA, TMAO and an unknown compound. Arsenobetaine, although present in all feed, control and As-rich, was measured only in the control crickets. To assess the bio-accessibility of the As species, crickets were subjected to simulated gastrointestinal digestion. The results showed that majority of As was extracted in saliva, followed by gastric and intestinal juice, which mass fraction was equal to residue. Over 78% of total As was shown to be bio-accessible with methylated species reaching 100% and iAs over 79% bio-accessibility. Additionally, arsenite and arsenate have shown different distributions between sequential leachate solutions. Bioaccumulation of As was observed in the studied crickets although it does not seem to occur to the same extent at higher exposure levels.

Arsenic speciation in sea cucumbers: Identification and quantitation of water-extractable species.

With the constant quest for new sources of superfoods to supplement the largely nutrient deficient diet of the modern society, sea cucumbers are gaining increasing popularity. Three species of sea cucumbers, Cucumaria frondosa, Apostichopus californicus and Apostichopusjaponicus were collected from three geographical regions, Atlantic and Pacific coast of Canada and Yellow sea/ East China sea in China, respectively. These organisms were sectioned into parts (body wall, tentacles, internal organ, skin and muscle) and analysed for total arsenic (As) by inductively coupled plasma mass spectrometry (ICP-MS) and As species by high-performance liquid chromatography (HPLC) coupled to ICP-MS. Normal and reversed sequential extractions were optimised to address As distribution between lipids (polar and non-polar) and water-extractable fractions. Two extraction methods for water-extractable As were compared in terms of the number and the amount of extracted species. The results revealed that total As concentration and As species distribution varies significantly between sea cucumbers species. Total As in studied body parts ranged between 2.8 ± 0.52 and 7.9 ± 1.2 mg kg-1, with an exception of the muscle tissue of A. californicus, where it reached to 36 ± 3.5 mg kg-1. Arsenobetaine (AsB) was the most abundant As species in A. californicus and A.japonicus, however, inorganic As represented over 70% of total recovered As in the body parts of C. frondosa. Arsenosugars-328 and 482 were found in all studied body parts whereas arsenosugar-408 was only found in the skin of A. californicus. This is the first time that such a variation in As species distribution between sea cucumber species has been shown.

Stabilization and Solvent Driven Crystal-to-Crystal Transition between New Bismuth Halides.

The investigations of bismuth halide chemistry in DMSO/MeOH solutions led to the discovery of a new solvent-stabilized compound with a chemical formula of Cs3BiBr6·3DMSO. In addition, a new phase of Cs3BiBr6 was generated as a result of a crystal-to-crystal transition driven by the change in the solvent composition. The solvent stabilized Cs3BiBr6·3DMSO adopts an orthorhombic P212121 type crystal structure with unit cell dimension of a = 13.6160(6) Å, b = 14.4359(8) Å, and c = 14.6487(7) Å. Bulk single crystals of Cs3BiBr6·3DMSO with average size of 4.5 × 3.5 × 3.5 mm3 were grown by the antisolvent crystal growth method. With the change of the solvent composition from 2:1 DMSO: MeOH to 1:1 DMSO: MeOH, the single crystals of Cs3BiBr6·3DMSO underwent a crystal-to-crystal transition yielding another structurally distinct Cs3BiBr6 phase, with a tetragonal P42/m type structure and unit cell dimensions of a = 9.8394(5) Å, b = 9.8394(5) Å, and c = 8.0950(6) Å. Both compounds exhibit isolated BiBr6 octahedral resembling the structures of the zero-dimensional (0D) perovskites.