Selenium and tellurium concentrations of Carboniferous British coals

The authors wish to thank Kier Group, the British Coal Utilisation Research Association (BCURA) and Uniper (E.On) for kindly providing coal samples. The authors are grateful to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), and Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS) for supporting this study. The authors are grateful for the thorough and constructive comments from two anonymous reviewers, as well as the careful editorial handling of Prof. Ian Somerville. This work was supported by the NERC under Grant number NE/L001764/1.Peer reviewedPublisher PD

Determination of Se at low concentration in coal by collision/reaction cell technology inductively coupled plasma mass spectrometry

The authors are grateful to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Grant 309297/2016-8), Instituto Nacional de Ciência e Tecnologia de Bioanalítica – INCTBio (CNPq Grant Nr. 573672/2008-3) and Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS, Grants16/2551-0000 (182-0) and 16/2551-0000516-8) for supporting this study. Funding for the sample collection provided by NERC Security of Supply programme UK (grant NE/L001764/1).Peer reviewedPostprin

Development of methods for Mg, Sr and Pb isotopic analysis of crude oil by MC-ICP-MS : addressing the challenges of sample decomposition

New approaches in isotope geochemistry require the development of novel methods for the isotopic analysis of crude oil, a typically complex and very hard to digest organic geological matrix. In this work, methods were developed for the determination of isotope ratios of Mg, Sr and Pb in crude oil by multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). Two sample preparation methods, (i) microwave-assisted wet digestion within an ultra-high pressure digestion cavity (MAWD-PDC) and (ii) solubilization of inorganic solids as obtained after the ASTM D4807 test method, were evaluated. Using MAWD-PDC, up to 0.5 g of crude oil was efficiently digested using only 6 mL of 14.4 mol L-1 HNO3 (75 min, temperature up to 250 degrees C). MAWD-PDC was shown to be a suitable sample preparation method for subsequent determination of Mg, Sr and Pb isotope ratios. On the other hand, the ASTM method does not require sophisticated equipment. With this approach up to 10 g of oil can be dissolved in toluene and filtered through a nylon membrane and elements present as inorganic solids, such as Mg and Sr, are retained on the membrane and can be easily recovered in water. However, Pb was not recovered. Column chromatographic protocols for target element isolation were fine-tuned for each analyte to ensure quantitative yields. No statistical difference was observed between the results for Mg and Sr isotope ratios obtained using both sample preparation methods. A proof-of-concept study showed that the Mg-Sr-Pb isotopic composition of the Brazilian crude oils was within the range observed for seawater and the deposit bedrock, suggesting that the methods developed can be considered as promising tools to decipher the formation history of oil reservoirs

Microwave-Induced Combustion of Coal for Further Sulfur Determination by Inductively Coupled Plasma Optical Emission Spectrometry or Ion Chromatography

In this work, a method using microwave-induced combustion (MIC) was optimized in order to obtain a fast, simple, efficient and greener sample preparation method for coal digestion and further determination of sulfur by inductively coupled plasma optical emission spectrometry (ICP OES). Accuracy was evaluated by comparison of the results with those obtained using elemental analysis by UV-fluorescence, microwave-assisted acid digestion with determination by ICP OES and by analysis of certified reference materials of coal. Some parameters that influence MIC method, such as the type and concentration of absorbing solution, the necessity of using a reflux step as well as the cooling time were carefully optimized. No statistical difference was observed for combustion without reflux followed by 5 min of cooling, in comparison to the reference values obtained by elemental analysis. Complete digestion was obtained with this fast and simple method (total digestion program required only 6 min) and using a diluted acid solution for quantitative recovery. The feasibility of digests for sulfur determination as sulfate by ion chromatography (IC) with conductivity detection was also demonstrated. The possibility of determining other elements, commonly monitored in coals, is another advantage of this high-efficiency digestion method (MIC) combined with the multielemental capacity of ICP OES or IC instruments

Microwave-Induced Combustion of Coal for Further Sulfur Determination by Inductively Coupled Plasma Optical Emission Spectrometry or Ion Chromatography

In this work, a method using microwave-induced combustion (MIC) was optimized in order to obtain a fast, simple, efficient and greener sample preparation method for coal digestion and further determination of sulfur by inductively coupled plasma optical emission spectrometry (ICP OES). Accuracy was evaluated by comparison of the results with those obtained using elemental analysis by UV-fluorescence, microwave-assisted acid digestion with determination by ICP OES and by analysis of certified reference materials of coal. Some parameters that influence MIC method, such as the type and concentration of absorbing solution, the necessity of using a reflux step as well as the cooling time were carefully optimized. No statistical difference was observed for combustion without reflux followed by 5 min of cooling, in comparison to the reference values obtained by elemental analysis. Complete digestion was obtained with this fast and simple method (total digestion program required only 6 min) and using a diluted acid solution for quantitative recovery. The feasibility of digests for sulfur determination as sulfate by ion chromatography (IC) with conductivity detection was also demonstrated. The possibility of determining other elements, commonly monitored in coals, is another advantage of this high-efficiency digestion method (MIC) combined with the multielemental capacity of ICP OES or IC instruments

Determination of Se and Te in coal at ultra-trace levels by ICP-MS after microwave-induced combustion

A method for ultra-trace determination of Se and Te in coal by inductively coupled plasma mass spectrometry (ICP-MS) was developed. Samples (up to 500 mg) were prepared by microwave-induced combustion (MIC) in a closed system pressurized with 20 bar of oxygen. Inorganic acids or their mixtures were evaluated as absorbing solution. Using HNO3 + HCl (1 + 1), results obtained for Se and Te after sample preparation by MIC agreed with those obtained by reference methods, microwave-assisted wet digestion (MAWD) using concentrated HNO3 and HF, and solid sampling electrothermal vaporization inductively coupled plasma mass spectrometry (SS-ETV-ICP-MS), and also with a certified reference material of coal (NIST 1632c) for Se. Very low limits of quantification (LOQ) were obtained: 0.002 and 0.007 mg kg1 for Se and Te, respectively. Major elements were determined in final solutions obtained by MAWD and MIC, and their concentration in solutions of MIC was negligible (<10 mg L1), minimizing the risk of interference in ICP-MS analysis. The proposed method was applied to samples of coal from the United Kingdom, with a wide range of inorganic composition (from 3 to 41% ash content), showing its robustness and feasibility for routine analysis. Se concentration ranged from 0.291 to 11.5 mg kg1, and Te was mainly found at ultra-trace levels (<0.007 to 0.11 mg kg1). The proposed method presents several advantages over the reference methods, such as the use of a higher sample mass, low LOQs and, an important aspect, no need of using HF

Selenium and tellurium concentrations of British coals

Standard mode and collision/reaction cell mass spectroscopy methods have been utilised in order to overcome spectral interferences and provide ultra-low quantification of selenium (Se) and tellurium (Te) in British coals for the first time. The accurate detection of Se and Te in coals is becoming increasingly important, as coals and pyrite have been identified as potentially significant trace element sources. The mean Se concentration of British coals bear comparison to that of world coals, with anomalous Se content (concentrations above 4 mg/kg) across westerly exposures, often coinciding with high sulphur (S) content and visible pyrite. New Te data for British coals gives a mean concentration of 0.02 mg/kg, with anomalous Te in Ayrshire. There is a positive correlation in the Te/Se ratio across the sample set. The close relationship between Se and Te, as well as Se-Te with both early syngenetic and later cleat filling pyrite, confirms an important role for sulphides in Se and Te sequestration in British coals. The high Se-Bowland Shale and/or Ordovician volcanics may have provided the trace element source British coals of similar or younger age. Regional intrusive activity (shallow Se and Te concentrations of British coals LB draft manuscript tabular intrusions or more extensive plutons) and episodes of intense deformation can alter the thermal maturity of coals, and may have driven the movement of trace element-rich fluids through strata, locally enriching coals in Se and Te

Low cost sample preparation method using ultrasound for the determination of environmentally critical elements in seaweed

In this study, ultrasound (US) was evaluated for As, Cd, Pb, Mn, Sr and V extraction from seaweed samples. The following parameters of ultrasound-assisted extraction (UAE) using an US bath were: frequency (25 to 130 kHz), amplitude (30 to 100%), temperature (30 to 80 °C), sample mass (50 to 200 mg), extractant concentration (1 to 3 mol L−1 of HNO3) and treatment time (5 to 30 min). Acoustic density and power density distribution were calculated using the calorimetric method and mapping of the acoustic pressure distribution was also evaluated. The optimized UAE conditions were 200 mg of sample in 10 mL of 2 mol L−1 HNO3 and 30 min of sonication in a 25 kHz US bath (37.2 ± 4.0 W L−1) at 70% of amplitude and 70 °C. Analytes were quantified using inductively coupled plasma mass spectrometry and results were compared with values obtained using “silent” conditions (magnetic or mechanical stirring at 500 rpm, and without stirring), and a reference method based on microwave-assisted wet digestion (MAWD). The UAE method demonstrated the best extraction efficiency (higher than 95%) for all analytes, especially for As, Cd and V, with lower standard deviations (up to 5%) and lower blank values in comparison with the silent conditions. The proposed UAE method was more advantageous than the reference method, being faster, simpler, safer, more environmentally friendly, and with higher detectability (lower limits of quantification, from 0.0033 to 1.34 µg g−1). In addition, negligible blank values were obtained for UAE and no interference were observed in the determination step. Furthermore, the optimized UAE method was applied for Antarctic seaweed samples and comparison with results obtained by MAWD was satisfactory. In this sense, UAE is demonstrated to be a suitable option for sample preparation of seaweed samples and further determination of environmentally critical elements avoiding the use of concentrated reagents as in the MAWD reference method