The Development of a Rapid, Cost-Effective, and Green Analytical Method for Mercury Speciation.

Mercury is a naturally occurring metal found in various inorganic and organic forms within the environment. Due to its high toxicity, there is global concern regarding human exposure to this element. The combination of high-performance liquid chromatography and inductively coupled plasma mass spectrometry (HPLC-ICP-MS) is commonly used to analyze the different forms of mercury in a sample due to its high sensitivity and ability to selectively detect mercury. However, the traditional HPLC-ICP-MS methods are often criticized for their lengthy analysis times. In this study, we have refined the conventional approach by transitioning to ultra-high performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (UHPLC-ICP-MS). This modification has resulted in significant reductions in runtime as well as reagent and argon usage, thereby offering a more rapid, environmentally friendly, and cost-effective method. We successfully adapted an HPLC-ICP-MS method to UHPLC-ICP-MS, achieving the analysis of Hg2+ and MeHg+ within 1 min with a mobile phase consumption of only 0.5 mL and a sample volume of 5.0 µL; this is a major advance compared to HPLC analysis with run times generally between 5 and 10 min. The method's performance was assessed by analyzing muscle and liver tissue samples (serving as reference material) from fish, demonstrating the versatility of the method in relation to different complex matrices.

Photo-generation of mercury cold vapor mediated by graphene quantum dots/TiO2 nanocomposite: On line time-resolved speciation at ultra-trace levels.

Mercury speciation was achieved using a nanocomposite, consisting of graphene quantum dots (GQDs) and TiO2 nanoparticles, to mediate photo-degradation of mercurial species into the Hg cold vapor detected by atomic spectrometry. Sample solution (containing Hg2+, CH3CH2Hg, and CH3Hg at hundreds of ng L-1) was placed in quartz tube containing formic acid solution (2% v/v) and microliter aliquot of GQDs/TiO2 nanocomposite dispersion (0.6 mg of nanocomposite). The tube was placed inside a photochemical reactor then, adapted to the mercury-dedicated spectrometer. Quantitative speciation was achieved taking advantage of the differences in UV photodegradation kinetics: Hg2+ (5 min), CH3CH2Hg (9 min) and CH3Hg (13 min). Gas-chromatography cold vapor atomic fluorescence spectrometry was used to confirm the evolution of the reactions over time during photo-reaction. The limits of detection were 10 ng L-1 for CH3CH2Hg and 7 ng L-1 for Hg2+ and CH3Hg.

Mercury and methylmercury levels in soils associated with coal-fired power plants in central-northern Chile.

Mercury pollution is a worldwide problem, and is associated with a number of natural and anthropogenic processes. The present work, conducted in Chile, a country that has traditionally depended heavily on fossil fuels for power generation, examines total mercury (THg) and monomethylmercury (MMHg) concentrations in soils across different sites exposed to coal fired power plant emissions. Samples from four selected (Renca, Laguna Verde, Las Ventanas, Huasco) and 1 control (Quintay) sites were analyzed using cold vapour and fluorescence spectroscopy (CV-AFS) for THg determination and chromatographic separation with atomic fluorescence detection (DI-GC-AFS) was followed for speciation analysis. From the sites analyzed, Renca and Las Ventanas showed high concentrations of total mercury, exhibiting ranges between 135 - 568 and 94-464 ng g-1 respectively, while Laguna Verde and Huasco exhibited lower values ranged 5-27 and 9-44 ng g-1 respectively. Conversely, analysis of MMHg concentrations showed that only Renca site possessed high values, ranging between 0.1 and 3.0 ng g-1, resulting in this site being considered contaminated. Conversely, other sites showed minimal values comparable to the control site (0.024 ±â€¯0.003 ng g-1) in terms of MMHg concentrations. An analysis of the differences between MMHg and THg concentrations in contaminated sites, suggests an overall absence of methylation in soils of Las Ventanas, probably related to the very high levels of soil heavy metals, especially copper. Moreover, the influence of the composition and physicochemical properties of the different soils on the mobility of the species was assessed. Results obtained (as Log Kd) were 3.5 and 4.1 for Renca and Las Ventanas respectively, suggesting low mobility of mercury species in the environment for both sites. Finally, the data obtained allowed us to establish a first approximation of the differences in concentration and mobility of total and MMHg associated with coal fired power plants emission in central-northern Chile, an area previously understudied in a country heavily dependent on fossil-fuels.

Fate of mercury in a terrestial biological lab process using Polypogon monspeliensis and Cyperus odoratus.

Mercury has been extracted in Queretaro, Mexico since the 1960s. The mining wastes were open-air disposal and these mercury wastes have polluted the zone. The aim of this research was to evaluate mercury's fate in lab scale terrestrial reactors considering the following mercury species: soluble, interchangeable, strongly bound, organic, and residual ones. Soils were sampled in two former mines of Pinal de Amoles, Queretaro, Mexico (N 20° 58' to 21° 21' and West 99° 26' to 99° 43') with initial mercury concentrations were 424 ± 29 and 433 ± 12 mg kg-1 for "La Lorena" and "San Jose" former mines, respectively. Two vegetal species Polypogon monspeliensis and Cyperus odoratus were used and 20 reactors were constructed for the lab process. Total mercury was removed to 49-79% from both soils. Mercury elemental, exchangeable, and organic species had the most removal or exchange in the process. Metal uptake, by the plants, was of 5-6% for P. monspeliensis and 5-15% for C. odoratus. Also, mercury fate was estimated to the atmosphere to be 3.3-4.5 mg m-2 h-1 for both soils.

Speciation and quantification of Hg in sediments contaminated by artisanal gold mining in the Gualaxo do Norte River, Minas Gerais, SE, Brazil.

The Iron Quadrangle in SE Brazil was, in the eighteenth century, one of the most important Au producing regions of Brazil. In this region, gold is produced, even today, by artisanal methods that use Hg to increase the extraction efficiency with no control of Hg release to water systems and the atmosphere. In this context, the Gualaxo do Norte River is of particular interest; its springs are located in the Doce River basin, an important Brazilian basin that supplies water for 3.5 million people. The main goal of this work was to quantify and speciate the Hg in the sediments of the Gualaxo do Norte River using a direct mercury analyzer and gas chromatography-pyrolysis-atomic fluorescence detection system. Statistical analyses consisted of principal component analysis, aiming to assess interactions among elements and species and to group the variables in factors affecting the properties of sediment. The results show that total Hg (THg) and methylmercury (CH3Hg+) concentrations in samples ranged from 209 to 1207 µg kg-1 and from 0.07 to 1.00 µg kg-1, respectively (methylation percentages from 0.01 to 0.27%). Thermal desorption analysis showed that mercury is mainly present in the oxidized form, and correlation analyses pointed to a relationship between THg and MnO, indicating that manganese can oxidize and/or adsorb Hg. Together, MO and CH3Hg+ are important parameters in the third principal component, indicating the influence of OM on the methylation process. This first investigation on Hg methylation in this small-scale gold mining area points to the possibility of Hg bioaccumulation and to the need of better understanding the biogeochemical cycle of Hg in this area. Samples were collected in 2012, prior to the 2015 Fundão Dam disaster. The results are also a record of the characteristics of the sediment prior to that event.

Assessment of dispersive liquid-liquid microextraction for the simultaneous extraction, preconcentration, and derivatization of Hg2+ and CH3Hg+ for further determination by GC-MS.

This work reports the development of a dispersive liquid-liquid microextraction method for the simultaneous extraction, preconcentration, and derivatization of Hg(2+) and CH3Hg(+) species from water samples for further determination by GC-MS. Some parameters of the proposed method, such as volume and type of disperser and extraction solvent, and Na[B(C6H5)4] concentration were investigated using response surface methodology. Suitable recoveries were obtained using 80 µL C2 Cl4 (as extraction solvent), 1000 µL ethanol (as disperser solvent), and 300 µL 2.1 mmol/L Na[B(C6H5)4] (as derivatizing agent). Accuracy was evaluated in terms of recovery and ranged from 87 to 99% with RSD values <7%. In addition, a certified reference material of water (NIST 1641d) was analyzed and agreed with the certified value about 107% (for Hg(2+)), with RSD values <8.5%. LODs were 0.3 and 0.2 µg/L, with enrichment factors of 112 and 115 for Hg(2+) and CH3Hg(+), respectively. The optimized method was applied for the determination of Hg(2+) and CH3Hg(+) in tap, well, and lake water samples.