A more quantitative extraction of arsenic-containing compounds from seafood matrices is essential in developing better dietary exposure estimates. More quantitative extraction often implies a more chemically aggressive set of extraction conditions. However, these conditions may result in undesirable chemical changes in the native arsenicals which may further complicate the toxicological risk assessment. This balance between quantitative extraction and species-specific integrity may be best addressed by using simulated gastric juice as an extraction solvent to mimic 'bioavailability'. This, conceptually, should extract the bioavailable fraction and induce any chemical changes that would occur because of ingestion. The most chemically labile species associated with seafood are thought to be the arsenosugars and for this reason their chemical stability is investigated in this study. Four arsenosugars (3-[5'-deoxy-5'-(dimethylarsinoyl)-beta-ribofuranosyloxy]-2-hydroxypropylene glycol, As(328); 3-[5'-deoxy-5'-(dimethylarsinoyl)-beta-ribofuranosyloxy]-2-hydroxypropanesulfonic acid, As(392); 3-[5'-deoxy-5'-(dimethylarsinoyl)-beta-ribofuranosyloxyl-2-hydroxypropyl hydrogen sulfate, As(408); and 3-[5'-deoxy-5'-(dimethylarsinoyl)-beta-ribofuranosyloxy]-2-hydroxypropyl-2,3-hydroxypropyl phosphate, As(482)) were isolated from seaweed extracts and subjected to simulated gastric juice and acidic conditions which mimic the stomach's pH of 1.1. Three acid solutions were used to test the chemical stability of the arsenosugars: simulated gastric juice, 78 mM nitric acid and 78 mM hydrochloric acid. The composition of the solutions was monitored over time (up to 48 h) using IC-ICP-MS for detection. The arsenosugars were found to degrade at the rate of 1.4% per h at 38 degrees C and 12.2% per h at 60 degrees C. The plots of percent conversion versus time were found to be independent of the starting arsenosugar and all had r2 values of greater than 0.97. A single common degradation product was observed in all the stability studies. A mass balance between the starting arsenosugar (As(392), As(408) and As(482)) and the degradation product was conducted with each set of experiments. This mass balance indicated that the degradation process did not produce any unchromatographable species. This degradation product was tentatively identified as As(254) as determined by ESI-MS/MS spectral data. An acid hydrolysis mechanism was proposed for the formation of As(254) from each of the native arsenosugars by hydrolysis at the C-1 carbon on the ribose ring.

Palladium-exchanged zeolites are candidate materials for passive NO x adsorption in automotive exhaust aftertreatment, where mononuclear Pd cations behave as precursors to the purported NO x adsorption sites. Yet, the structures of zeolite lattice binding sites capable of stabilizing mononuclear Pd 2+ ions, and the mechanisms that interconvert agglomerated PdO and Pd domains into mononuclear Pd 2+ ions during Pd redispersion treatments, remain incompletely understood. Here, we use a suite of spectroscopic methods and quantitative site titration techniques to characterize mononuclear and agglomerated Pd species on zeolites with varying material properties and treatment history. Aqueous-phase methods to introduce Pd onto NH 4 -form zeolites initially form mononuclear [Pd(NH 3 ) 4 ] 2+ complexes, but subsequent thermal treatments (573−723 K; air) lead to in situ formation of H 2 that first reduces Pd 2+ to metallic Pd domains, which are then oxidized by air to PdO domains. Progressive treatment of Pd-zeolites in air to higher temperatures (723−1023 K) converts larger fractions of agglomerated PdO to mononuclear Pd 2+ , as quantified by H 2 temperature programmed reduction, because higher temperature treatments facilitate Pd redispersion toward deeper locations within chabazite (CHA) crystallites, which is corroborated by complementary titrimetric and spectroscopic data. Pd-CHA zeolites synthesized with similar bulk Pd and framework Al content, but varying framework Al arrangement, provide evidence that six-membered rings (6-MR) hosting paired Al sites (Al−O−(Si−O) x −Al, x = 1, 2) stabilize Pd 2+ ions and that otherwise isolated Al sites can stabilize [PdOH]+ species, identifiable by an IR OH stretch at 3660 cm −1 . These findings clarify the underlying chemical processes and gas environments that cause Pd agglomeration in zeolites and their subsequent redispersion to mononuclear Pd 2+ ions, which prefer binding at 6-MR paired Al sites in CHA, and indicate that higher temperature air treatments lead to more uniform Pd spatial distributions throughout zeolite crystallites.

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The selectivity and the ability to obtain structural information from detection schemes used in arsenic speciation research are growing analytical requirements driven by the growing number of arsenicals extracted from natural products and the need to minimize misidenti®cation in exposure assessments. Three arsenosugars were extracted from ribbon kelp utilizing accelerated solvent extraction. The three arsenosugars were separated from other arsenicals with near baseline resolution using a PRP-X100 column and a 20 mM (NH 4) 2 CO 3 mobile phase at a pH of 9 with IC-ICP-MS detection. Utilizing these chromatographic conditions, the molecular weight was determined for each arsenosugar utilizing ion chromatography-electrospray ionization-mass spectrometry (IC-ESI-MS) in the positive ion mode. The molecular weight and retention times for the three arsenicals are 328 u (4.6 min), 482 u (8.2 min) and 392 u (14.2 min). The IC-ESI-MS-MS spectra from each of the arsenosugars were compared to the spectra reported in the literature, which were obtained via direct infusion of standard materials. All three MS-MS spectra contain m/z 237, 195 and 97, which are fragments of the base dimethylarsinylriboside common to all the arsenosugars. Adequate sensitivity for each arsenical was achieved using a 6.1 ng and a 22 ng injection for IC-ESI-MS and IC-ESI-MS-MS, respectively. Given the unavailability of standards, the arsenosugar distribution was determined via relative chromatographic areas using IC-ICP-MS. The IC-ICP-MS indicated the presence of an arsenic heteroatom within the same retention windows in which the arsenosugars were detected via IC-ESI-MS. The IC-ESI-MS and IC-ESI-MS-MS detection scheme provided structural information but at reduced sensitivity. In an attempt to preserve sensitivity and improve selectivity of the IC-ICP-MS, an on-line membrane hydride generation detection scheme was evaluated. The hydride system indicated that the three unknown peaks (arsenosugars) were not hydride active, thereby simplifying the chromatographic resolution needed to quantitate the more toxicologically important arsenicals, such as MMA, DMA, As(III) and As(V), while minimizing the potential for misidenti®cation.

The native distribution of As(III) and As(v) in drinking water supplies can influence the treatment removal strategy. The stability of As(III) and As(v) in iron-rich drinking waters can be affected by the formation of Fe precipitates (Fe oxides and/or hydroxides designated by "FeOOH"). These precipitates (ppts) can form during the transport of the sample to the laboratory for arsenic speciation analysis. The analysis of the ppt indicates considerable loss of the aqueous arsenic species (As(aq)) to the solid phase "FeOOH" ppt. Studies of laboratory reagent water containing both As(III) and Fe(III) indicate that the resulting "FeOOH" ppt contained a mixture of As(III) and As(v) with near quantitative removal of the As(aq) in 18 hr. The corresponding aqueous fraction after filtration through a 0.45 microm filter was composed primarily of As(v). The formation of "FeOOH" ppt and the loss of As(aq) to the ppt can be virtually eliminated by the use of EDTA, which sequesters the FeIII). Reagent water fortified with Fe(III), As(III) and EDTA produced less than a 1 ppb change in the As(III)aq concentration over 16 d. The EDTA treatment was also tested on three well waters with different native As(III )/As(v) ratios. The native distribution of As(III)/As(v) was stabilized over a period of 10 d with a worst case conversion of As(III) to As(v) of 2 ppb over a 30 d period. All well waters not treated with EDTA had dramatic losses (a factor of 2-5) of As(aq) in less than 1 d. These results indicated that EDTA preservation treatment can be used to preserve As(aq) in waters where the predominant species is the reduced form [As(III)] or in waters which the predominant species is the oxidized form [As(v)]. This preliminary investigation of EDTA to preserve As species in Fe-rich waters indicates stability can be achieved for greater than 14 d.

The heteropolyanion [PW 11 O 39 RhCl] 5-(1-Cl) was synthesized by hydrothermal reaction of [PW 11 O 39 ] 7and RhCl 3 at 150 °C for 20 h. The tetramethylammonium salt of 1-Cl was characterized by elemental analysis, 31 P and 183 W NMR, and solution molecular weight determination by ultracentrifugation (found 2744 ( 63, calcd 2816). The cyclic voltammogram of 1-Cl shows an irreversible reduction wave at -0.45 V vs Ag/AgCl, and controlled potential reduction at -0.5 V generates the dimeric metal-metal bonded species [(PW 11 O 39 Rh) 2 ] 10-(2). The composition and structure of 2 have been confirmed by elemental analysis of the cesium salt, analytical ultracentrifugation (ionic weight 5821 ( 186, calcd 5561), P and W NMR, and a limited structural analysis of the potassium salt, which revealed a Rh-Rh bond length of 2.52(2) Å (K 10 [(PW 11 O 39 Rh) 2 ]‚xH 2 O, triclinic, P1 h; a ) 12.703(6), b ) 17.868(8), and c ) 19.131(9) Å; R ) 96.56(2), β ) 97.12(2), and γ ) 91.318(33)°; Z ) 2; V ) 4278(3) Å 3 ). Aqueous solutions of 2 show an absorption band at 720 nm attributed to the π*fσ* transition of the metal-metal bond. Photolysis (λ > 670 nm) of acetone solutions of 2 with PhCH 2 Br yields [PW 11 O 39 RhBr] 5-(1-Br) and PhCH 2 CH 2 Ph. Oxidation of 2 by air, Br 2 , and hypochlorite yields [PW 11 O 39 Rh(H 2 O)] 4-(1-aq), 1-Br, and 1-Cl, respectively. Photochemical, electrochemical, and ligand substitution routes to other [PW 11 O 39 RhL] nspecies, L ) I -, CN -, CH 3 COO -, pyridine, or S-bonded dimethyl sulfoxide, are described. Each of these complexes has a characteristic P NMR resonance, and mixtures are separable by chromatography on Sephadex.

An accelerated solvent extraction (ASE) device was evaluated as a semi-automated means of extracting arsenicals from ribbon kelp. The effect of the experimentally controllable ASE parameters (pressure, temperature, static time, and solvent composition) on the extraction efficiencies of arsenicals from seaweed was investigated. The extraction efficiencies for ribbon kelp (approximately 72.6%) using the ASE were fairly independent (< 7%) of pressure, static time and particle size after 3 ASE extraction cycles. The optimum extraction conditions for the ribbon kelp were obtained by using a 3 mL ASE cell, 30/70 (w/w) MeOH/H2O, 500 psi (1 psi = 7 KPa), ambient temperature, 1 min heat step, 1 min static step, 90% vol. flush, and a 120 s purge. Using these conditions, two other seaweed products produced extraction efficiencies of 25.6% and 50.5%. The inorganic species present in the extract represented 62.5% and 27.8% of the extracted arsenic. The speciation results indicated that both seaweed products contained 4 different arsenosugars, DMA (dimethylarsinic acid), and As(V). One seaweed product also contained As(III). Both of these seaweed products contained an arsenosugar whose molecular weight was determined to be 408 and its structure was tentatively identified using ion chromatography-electrospray ionization-mass spectrometry/mass spectrometry (IC-ESI-MS/MS).

We identified an individual who was coinfected with two SARS-CoV-2 variants of concern, the Beta and Delta variants. The ratio of the relative abundance between the two variants was maintained at 1:9 (Beta:Delta) in 14 days. Furthermore, possible evidence of recombinations in the Orf1ab and Spike genes was found.