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Abstract Multivitamin/mineral (MVM) supplements possess highly saline matrix which, unless eliminated, precludes accurate determination of trace amounts of toxic metal impurities by inductively coupled plasma mass spectrometry (ICP-MS). Multi-step separations (up to four-steps) are described in literature; often for single element determinations due to the difficulties in removing the matrix components. In this study, we developed a three-step sequential coprecipitation procedure for simultaneous separation of As and Cd impurities from MVM supplements for determination by ICP-MS. The procedure provided effective elimination of salt matrix, including Ca, Mg and KCl along with the interfering molybdenum (Mo) and tin (Sn) from MVM solutions. KCl, Mo and Sn were reduced by two-step Mg(OH) 2 coprecipitation to about 34 μg mL−1 K (ca. 31 μg mL−1 Cl) and 0.4 μg mL−1 Mo. Levels of Sn and Na were not significant. A third coprecipitation of the resulting MVM solution with HF + NH 4 OH mixture precipitated virtually all Ca and Mg to as low as 1 and 10 μg mL−1, respectively. The recoveries for As and Cd in the spiked MVM solutions were about 96% and 95%, respectively. The accuracy of the method was validated with analysis of multivitamin/multielement tablets certified reference material (SRM 3280). Experimental values were 112 ± 37 ng g−1 for 75As, and 76 ± 5, 79 ± 5, and 78 ± 7 ng g−1 for 110Cd, 111Cd and 114Cd isotopes, respectively, that were not significantly different from the certified values of As (132 ± 44 ng g−1) and Cd (80.2 ± 0.9 ng g−1) at 95% confidence level. Several commercially available MVM supplements were analyzed with the procedure. Mean As levels measured in the tablets varied between 24 and 128 ng g−1 and that for Cd were between 28 and 125 ng g−1 indicating total amount of As or Cd ingested per serving size were below the safe daily exposure limits. In addition, the results obtained for As and Cd with the procedure were lower in comparison to the values reported in literature indicating that ICP-MS analysis of complex MVM supplements could be prone to higher risks of inaccuracy without removal of interfering matrix. Highlights • Sequential coprecipitation is developed to determine toxic metal impurities from multivitamin/mineral (MVM) supplements. • The procedure is faster and allows simultaneous separation of As and Cd from MVM matrix. • KCl matrix, and interfering Mo and Sn is effectively removed. • Persistent Ca and Mg is completely eliminated from MVM solutions. • The method is validated with analysis of SRM 3280 for As and Cd. • Commercial MVM supplements contain lower As and Cd impurities than minimum risk levels (MRLs). [ABSTRACT FROM AUTHOR]

Abstract A procedure is developed for selective extraction of methylmercury (CH 3 Hg+) from heavily Hg-contaminated soils and sediments for determination by chemical vapor generation inductively coupled plasma mass spectrometry (CVG-ICP-MS). Soils artificially contaminated with 40 μg g−1 inorganic mercury (Hg2+) or methylmercury chloride (CH 3 HgCl) were agitated by shaking or exposing to ultrasounds in dilute hydrochloric acid (HCl) or nitric acid (HNO 3) solutions at room temperature. Extractions in HCl (5 or 10% v/v) resulted in substantial leaching of Hg2+ from soils, whereas 5% (v/v) HNO 3 provided selectivity for quantitative extraction of CH 3 Hg+ with minimum Hg2+ leaching. Agitation with ultrasounds in 5% (v/v) HNO 3 for about 3 min was sufficient for extraction of all CH 3 Hg+ from soils. Coprecipitations with Fe(OH) 3 , Bi(OH) 3 and HgS were investigated for removal of residual Hg2+ in soil extracts. Hydroxide precipitations were not effective. Thiourea or l -cysteine added to soil extracts prior to hydroxide precipitation improved precipitation of Hg2+, but also resulted in removal of CH 3 Hg+. HgS precipitation was made with dilute ammonium sulfide solution, (NH 4) 2 S. Adding 30 μL of 0.35 mol L−1 (NH 4) 2 S to soil extracts in 5% (v/v) HNO 3 resulted in removal of all residual Hg2+ without impacting CH 3 Hg+ levels. Vapor generation was carried out by reacting Hg2+-free soil extracts with 1% (m/v) NaBH 4. No significant interferences were observed from (NH 4) 2 S on the vapor generation from CH 3 Hg+. The slopes of the calibration curves for CH 3 HgCl standard solutions in 5% (v/v) HNO 3 with and without (NH 4) 2 S were similar. Limits of detection (LOD, 3s method) were around 0.08 μg L−1 for 5% (v/v) HNO 3 blanks (n = 10) and 0.10 μg L−1 for 5% (v/v) HNO 3 + 0.005 mol L−1 (NH 4) 2 S blanks (n = 10). Percent relative standard deviation (%RSD) for five replicate measurements varied between 3.1% and 6.4% at 1.0 CH 3 HgCl level. The method is validated by analysis of two certified reference materials (CRM); purely Methylmercury sediment (SQC1238, 10.00 ± 0.291 ng g−1 CH 3 Hg+) and Hg-contaminated Estuarine sediment (ERM – CC580, 75 ± 4 ng g−1 CH 3 Hg+ and 132 ± 3 μg g−1 total Hg). CH 3 Hg+ values for SQC1238 were between 13.0 and 13.2 ng g−1, and 79 and 81 ng g−1 for ERM – CC580. Hg-contaminated soils (57–96 μg g−1 total Hg) collected from the floodplains of Oak Ridge, TN were analyzed for CH 3 Hg+ using the procedure by CVG-ICPMS. CH 3 Hg+ levels ranged from 30 to 51 ng g−1 and did not correlate with total Hg levels (R2 = 0.01). Graphical abstract Image 1 Highlights • Methylmercury was selectively separated from Hg-contaminated soils. • Dilute HNO 3 minimized leaching of Hg2+ from soil to solution. • Ultrasound-assisted agitation ensured fast extraction of methylmercury. • Coprecipitation with ammonium sulfide eliminated residual Hg2+ effectively from soil extracts. • Chemical vapor generation was optimized for determination of methylmercury from Hg-contaminated soils by ICP-MS. [ABSTRACT FROM AUTHOR]

Mercury in aqueous systems can be present in different chemical forms. Of these, dissolved elemental Hg(0) (DEM) is of great importance because it can readily be partitioned between air and water. Analytical methods used for determining DEM are conventionally based on removal of Hg(0) by purging, pre-concentration on gold and detection by either cold vapour atomic absorption (CV-AAS) or atomic fluorescence spectrophotometry (CV-AFS). At present, there is no agreed protocol for the measurement of DEM in aqueous samples. A new method is described here, which is based on continuous stripping of DEM by mercury-free nitrogen in a flow injection mode and detection by CV-AAS. The partitioning of DEM between aqueous and gas phases is largely dependent on the composition of the former. Moreover, calibration using the standard addition method is not possible due to the reactivity of DEM introduced from calibration solutions. Calibration is therefore done by reference measurements using a manual method for DEM involving quantitative removal and CV-AFS detection. DEM is then determined in the water sample by applying the partitioning factor. The optimised method is precise, sensitive and linear over a wide concentration range. It has provided comparable results with the manual method when applied on board a research vessel in the Mediterranean Sea (0.02–0.05 ng L−1) and during a pilot laboratory-scale experiment on industrial aqueous media from wet flue gas desulphurisation (WFGD) equipment (2–300 ng L−1). [ABSTRACT FROM AUTHOR]

Dissolved gaseous mercury (DGM) was studied in surface and deep waters of the Mediterranean Sea over the last 15 years during several oceanographic cruises on board the Italian research vessels Urania and Minerva Uno, covering the Western and Eastern Mediterranean Basins as well as Adriatic Sea as its northernmost part. DGM was measured together with other mercury species (RHg - reactive Hg, THg - total Hg, MeHg - monomethyl Hg and DMeHg - dimethylmercury), and with water quality parameters in coastal and open sea deep water profiles. DGM represents a considerable portion of THg (on average 20%) in Mediterranean waters. Spatial and seasonal variations of measured DGM concentrations were observed in different identified water masses. DGM was the highest in the northern Adriatic, the most polluted part of the Mediterranean Sea as a consequence of Hg mining in Idrija and heavy industry in northern Italy, and near the Gulf of Lion. Generally, average DGM concentration was higher in the West and East Mediterranean Deep Waters (WMDW and EMDW) and Levantine Intermediate Water (LIW) than in overlaying Modified Atlantic Water (MAW); however, it was the highest in N Adriatic Surface waters (NAdSW) and consequently in outflowing Adriatic Deep Waters (AdDW). In deep water profiles the portion of DGM typically increased at depths with oxygen minimum and then towards the bottom, especially in areas with strong tectonic activity (Alboran Sea, Strait of Sicily, Tyrrhenian Sea), indicating its bacterial and/or geotectonic origin. During oceanographic cruises in 2011 and 2015 in the Tyrrhenian Sea, novel methods for continuous DGM determination in surface waters (Wangberg and Gardfeldt, 2011, Begu et al., 2016) were applied and compared to the standard method, and showed good agreement. [ABSTRACT FROM AUTHOR]

Abstract Microbial transformations of toxic monomethylmercury (MMHg) and dissolved gaseous mercury (DGM) at the lower levels of the marine food web are not well understood, especially in oligotrophic and phosphorus-limited seas. To examine the effects of probable phosphorus limitation (PP-limitation) on relations between mercury (Hg) fractions and microorganisms, we determined the total mercury (THg), total methylated mercury (MeHg), DGM, and microbiological and chemical parameters in the Central Adriatic Sea. Using statistical analysis, we assessed the potential microbial effects on Hg transformations and bioaccumulation. Only in the absence of PP-limitation conditions (NO–PP-limitation) is MeHg significantly related to most chemical and microbial parameters, indicating metabolism-dependent Hg transformations. The heterotrophic activity of low nucleic acid bacteria (abundant in oligotrophic regions) seems responsible for most of Hg methylation under NO–PP-limitation. Under these conditions, DGM is strongly related to microbial fractions and chlorophyll a , indicating biological DGM production, which is probably not metabolically induced, as most of these relations are also observed under PP-limitation. MMHg biomagnification was observed through an increased bioaccumulation factor from microseston to mesozooplankton. Our results indicate that Hg transformations and uptake might be enhanced under NO–PP-limitation conditions, emphasizing their impact on the transfer of Hg to higher trophic levels. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

The mechanisms of mercury (Hg) microbial transformations in coastal marine water column are poorly understood. In an effort to study seasonal Hg transformation mechanisms and underlying processes in the coastal marine ecosystem of the Gulf of Trieste (northern Adriatic Sea), we have successfully applied the 197 Hg radiotracer technique in series of incubation experiments. This area is characterized by continuous Hg input from the Soča/Isonzo River as a consequence of nearly 500 years of activity at the Idrija Mine (W Slovenia). The method proved to be valuable, since it allowed us to follow Hg transformations at concentrations similar to those found in the study site. During our study, Hg methylation in the marine water column could not be detected, suggesting that sediments are the principal methylation site and the source of MeHg to the water column. Conversely, the water column showed a pronounced Hg reduction potential, mostly of photochemical origin, suggesting that the Gulf of Trieste is a source of Hg 0 to the atmosphere. However, the high Hg reduction potential observed in autumn was most likely related to a phytoplankton (diatom) autumn bloom, indicated by high Chl a concentrations measured during that period. We hypothesize that the microbial reduction was either linked to the expression of mer genes or, a consequence of non-specific redox reactions. Variations in bacterioplankton community fingerprints (as determined by Denaturing Gradient Gel Electrophoresis) suggested that community structure had little influence on microbial Hg reduction potential. Nevertheless, our results indicate that in the absence of photochemistry, interactions between microbes and organic matter may enhance biogeochemical Hg 2 + reduction potential in some coastal marine environments. [ABSTRACT FROM AUTHOR]