Stability, preservation and storage of As(iii), DMA, MMA and As(v) in water samples.

Correct handling and preservation of water samples is crucial to ensure their integrity for arsenic speciation measurements. ISO TS 19620:2018 is a method for the determination of arsenic(iii) and arsenic(v) species in waters by liquid chromatography (LC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) or hydride generation atomic fluorescence spectrometry (HG-AFS). During the development of this method, a study was performed to establish the best practices for storage and preservation of samples to maintain the integrity of the arsenic speciation and stability. Four arsenic species were studied: arsenite (As(iii)), arsenate (As(v)), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in three different water types: deionised water, mineral water and natural river water. The effect of sample bottle material, light, storage temperature, and acidification were evaluated. When samples are acidified and refrigerated, they can reliably be stored for up to 12 weeks without significantly affecting the arsenic concentration and speciation. The sample bottle material and light had no affect on the speciation integrity or stability.

Determination of ultra-low volatile mercury concentrations in sulfur-rich gases and liquids.

Determining mercury (Hg) concentrations in a wide range of naturally occurring liquids (i.e., groundwater, hydrothermal fluids, acid mine drainage, submarine groundwater discharge, etc.) and gases, (i.e., volcanic and hydrothermal emissions, flue gas, natural gas, land fill gas, etc.) has obstacles due to the presence of H2S in many of such samples. The classical approach of trapping Hg on gold traps comes up against its limits due to "poisoning" of the traps by H2S and problems for its determination by cold vapor atomic fluorescence spectrometry (CV-AFS). Due to low concentrations of Hg in these sample types it is often necessary to collect large amounts of liquid or gas in excess of 20 L, which makes transport to the laboratory difficult. With this in mind we developed a portable method for the collection of Hg from gases and liquids rich in H2S. The method uses an impinger set-up with an alkaline trap followed by two potassium permanganate - sulfuric acid traps. The potassium permanganate (KMnO4) oxidizes elemental Hg vapor to Hg2+, which remains in the KMnO4 solution and thus can be analyzed by CV-AFS. Thus, rather than 25 L of sample, only a few mL have to be transported to the laboratory. A possible caveat of this approach is that naturally occurring gases are generally a mixture of several different gases, such as H2, CH4, SO2 and H2S, which can react with and thus consume KMnO4. The influence of various gas compounds at different concentrations were tested for their effect on the trapping of Hg by KMnO4. Hydrogen and CH4 did not cause any interference, while SO2 did react with the KMnO4. When the oxidizing capacity in the first KMnO4-trap was depleted due to SO2, Hg was trapped in the second KMnO4-trap, which acted as a safety trap. Good recoveries of 99.5 % were achieved for the Hg collected in both KMnO4-traps. Nevertheless, when H2S was introduced into the system, Hg recovery dropped by almost 50 %. This observation was attributed to the formation of mercury sulfide (HgS) in the trap when the oxidation capacity of the KMnO4-trap was consumed. HgS cannot be reduced by stannous chloride (SnCl2), which is necessary for detection by CV-AFS. The problem was overcome by adding an alkaline trap with the reductant sodium borohydride (NaBH4) in front of the two KMnO4-traps. In this trap H2S was converted to S2-, which does not reach the KMnO4-trap while at the same time NaBH4 prevented the oxidation of Hg to Hg2+ followed by precipitation as HgS. Good recoveries of 98.05 ±â€¯3.6 % (n = 3) were obtained for Hg when a volume of 1000 mL H2S was passed through the impinger train. Field testing of the method verified the effect of H2S on the trapping and ultimately the determination of Hg in the hydrothermal gas. With the alkaline trap we determined a Hg concentration of 358 ng m-3 Hg, while without the alkaline trap only 101 ng m-3 Hg. Thus, the set-up without the alkaline trap led to an underestimation of the real Hg concentration by 71.8 % and confirmed the necessity of an alkaline trap to overcome the interference of H2S.

Methylmercury varies more than one order of magnitude in commercial European rice.

Rice is known to accumulate methylmercury (MeHg) in the rice grains. MeHg as a neurotoxin impacts on the human central nervous systems and especially on the developing brain. In this exploratory study, 87 commercial rice products sold in Europe, including nine baby-rice products, were analyzed for total Hg and MeHg content. MeHg concentration in all rice products investigated range from 0.11 to 6.45µgkg(-1) with an average value of 1.91±1.07µgkg(-1) and baby-rice is not significantly different from other rice products. Total Hg ranges from 0.53 to 11.1µgkg(-1) with an average of 3.04±2.07µgkg(-1). MeHg concentrations in all rice products studied in this work would not exceed the provisional tolerable weekly intake (PTWI). 30% of all commercial market rice products exceeded 10% of the PTWI calculated for toddlers or 13% of products for adults with rice based diet.

Direct online HPLC-CV-AFS method for traces of methylmercury without derivatisation: a matrix-independent method for urine, sediment and biological tissue samples.

Mercury (Hg) is a global pollutant which occurs in different species, with methylmercury (MeHg) being the critical compound due to its neurotoxicity and bioaccumulation through the food chain. Methods for trace speciation of MeHg are therefore needed for a vast range of sample matrices, such as biological tissues, fluids, soils or sediments. We have previously developed an ultra-trace speciation method for methylmercury in water, based on a preconcentration HPLC cold vapour atomic fluorescence spectrometry (HPLC-CV-AFS) method. The focus of this work is mercury speciation in a variety of sample matrices to assess the versatility of the method. Certified reference materials were used where possible, and samples were spiked where reference materials were not available, e.g. human urine. Solid samples were submitted for commonly used digestion or extraction processes to obtain a liquid sample for injection into the analytical system. For MeHg in sediment samples, an extraction procedure was adapted to accommodate MeHg separation from high amounts of Hg(2+) to avoid an overload of the column. The recovery for MeHg determination was found to be in the range of 88-104% in fish reference materials (DOLT-2, DOLT-4, DORM-3), lobster (TORT-2), seaweed (IAEA-140/TM), sediments (ERM(®)-CC580) and spiked urine and has been proven to be robust, reliable, virtually matrix-independent and relatively cost-effective. Applications in the ultra-trace concentration range are possible using the preconcentration up to 200 mL, while for higher MeHg-containing samples, lower volumes can be applied. A comparison was carried out between species-specific isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SSID-GC-ICP-MS) as the gold standard and HPLC-CV-AFS for biological tissues (liver, kidney and muscle of pilot whales), showing a slope of 1.008 and R (2) = 0.97, which indicates that the HPLC-CV-AFS method achieves well-correlated results for MeHg in biological tissues.

Syntheses, emission properties and intramolecular ligand exchange of zinc complexes with ligands belonging to the tmpa family.

The zinc complexes [(L1)(2)Zn(MeOH)(2)](OTf)(2), [(L1)ZnCl(2)], [(L2)ZnCl(2)], [(L2)Zn(OTf)(H(2)O)]OTf and [(Me-bispic)ZnCl(2)] of the ligands N-[(2-pyridyl)methyl]-2,2'-dipyridylamine (L1), N-[bis(2-pyridyl)methyl]-2-pyridylamine (L2) and N-methyl-[bis(2-pyridyl)methyl]amine (Me-bispic) were synthesised and characterised. The first copper(I) complexes of the ligands L1 and L2 were also synthesised and structurally characterised. [(L1)ZnCl(2)] showed unexpected fluxional behaviour in solution and revealed an interesting intramolecular ligand exchange mechanism in the coordination sphere of the zinc ion. Furthermore, strong blue emission was observed under UV-light excitation.