Tiberiu Frentiu

Mercury determination in non- and biodegradable materials by cold vapor capacitively coupled plasma microtorch atomic emission spectrometry.

A new analytical system consisting of a low power capacitively coupled plasma microtorch (20 W, 13.56 MHz, 150 ml min(-1) Ar) and a microspectrometer was investigated for the Hg determination in non- and biodegradable materials by cold-vapor generation, using SnCl(2) reductant, and atomic emission spectrometry. The investigated miniaturized system was used for Hg determination in recyclable plastics from electronic equipments and biodegradable materials (shopping bags of 98% biodegradable polyethylene and corn starch) with the advantages of easy operation and low analysis costs. Samples were mineralized in HNO(3)-H(2)SO(4) mixture in a high-pressure microwave system. The detection limits of 0.05 ng ml(-1) or 0.08 μg g(-1) in solid sample were compared with those reported for other analytical systems. The method precision was 1.5-9.4% for Hg levels of 1.37-13.9 mg kg(-1), while recovery in two polyethylene certified reference materials in the range 98.7 ± 4.5% (95% confidence level).

A novel analytical system with a capacitively coupled plasma microtorch and a gold filament microcollector for the determination of total Hg in water by cold vapour atomic emission spectrometry

A novel, miniaturized analytical system of high sensitivity and precision based on atomic emission in a capacitively coupled plasma microtorch (13.56 MHz, 20 W, 200 mL min−1 Ar) equipped with a gold filament microcollector and a microspectrometer was investigated for total Hg determination in water. The method is based on cold vapour generation using SnCl2 and preconcentration on the microcollector followed by thermal desorption for 5 s and emission measurement at 253.652 nm. The microcollector consists of a gold filament of 80 μm diameter, 24 cm length and 43 turns encapsulated in a quartz capillary of 2.5 mm i.d., 4 mm o.d. supplied at 1.5 A. Due to very low thermal inertia, the fast, direct heating of the filament provides a high flow rate of Hg vapour toward plasma and hence sensitivity of the analytical system in the sub-ng L−1 Hg range. The optimal working conditions and figures of merit of the system are presented for Hg determination in drinking and river water, leachate of polyethylene terephthalate bottles and food packaging of biodegradable materials. At concentrations in the range of 0.06–57.4 ng L−1 the precision was 0.9–7.0%. The detection limit in solution was 0.02 ng L−1, while the absolute value was 0.5 pg. Validation of the system was carried out by analyzing a certified groundwater (ERM-CA615) that gave a recovery of 101 ± 2% for the certified concentration of 37.0 ± 0.4 ng L−1. The novel system can be prototyped as a substitute for existing systems based on atomic fluorescence or absorption.

Arsenic and antimony determination in non- and biodegradable materials by hydride generation capacitively coupled plasma microtorch optical emission spectrometry.

A sensitive method using a miniature analytical system with a capacitively coupled plasma microtorch (25 W, 13.56 MHz, 0.4 l min(-1) Ar) was developed and evaluated for the determination of As and Sb in recyclable plastics and biodegradable materials by hydride generation optical emission spectrometry. Given their toxicity, As and Sb should be subject to monitoring in such materials despite not being included within the scope of Restriction of Hazardous Substances Directive. The advantages of the proposed approach are better detection limits and lower analysis cost relative to conventional systems based on inductively coupled plasma optical emission and flame atomic absorption spectrometry with/without derivatization. Samples were subjected to acidic microwave-assisted digestion in a nitric-sulfuric acid mixture. Chemical hydride generation with 0.5% NaBH4 after the prereduction of As(V) and Sb(V) with 0.3% L-cysteine in 0.01 mol l(-1) HCl (10 min contact time at 90±5°C) was used. Under the optimal hydride generation conditions and analytical system operation the detection limits (mg kg(-1)) were 0.5 (As) and 0.1 (Sb), whereas the precision was 0.4-7.1% for 10.2-46.2 mg kg(-1) As and 0.4-3.2% for 7.1-156 mg kg(-1) Sb. Analysis of two polyethylene CRMs revealed recoveries of 101±2% As and 100±1% Sb.

Atmospheric pressure capacitively coupled plasma source for the direct analysis of non-conductive solid samples

An atmospheric pressure capacitively coupled device for the rf sputtering and direct analysis by AES of non-conductive solid samples was developed. It operates at 13.56 MHz, with Ar flow rates lower than 1 l min –1 and rf input powers between 20 and 50 W. With the aim of studying the expulsion mechanism and determining the analytical performance, the following materials were used: ZnO with known content of trace elements (Si, Pb, Cd and Na); four andesite standards with certified contents of Pb, Cu and Cr; and a synthetic (laboratory made) andesite standard. The expulsion mechanism depends on the rf power. Below 38 W, the sputtering rate is nearly constant and the atomisation is produced only by sputtering. At powers higher than 38 W, thermal evaporation will be present in addition to rf sputtering. All measurements for evaluating the analytical performance were made at optimum working parameters (rf power=36 W, Ar flow rate=0.5 l min –1 ). The detection limits are 0.3, 0.7, 1.0 and 0.9 µg g –1 for Na, Pb, Si and Cd, respectively, in the ZnO matrix and 0.8, 1.0 and 0.5 µg g –1 for Pb, Cr and Cu, respectively, in the andesite matrix. The dynamic range for Pb is about three orders of magnitude. The relative standard deviations for Pb in the certified standards are between 1.7 and 12.7% and the recoveries compared with the certified values are between 95 and 104% for the concentration range 5.8-35.1 µg g –1 .

Simultaneous determination of As and Sb in soil using hydride generation capacitively coupled plasma microtorch optical emission spectrometry – comparison with inductively coupled plasma optical emission spectrometry

A method using a miniature analytical system based on hydride generation capacitively coupled plasma microtorch optical emission spectrometry with a QE65 Pro microspectrometer was developed and evaluated for the simultaneous determination of As and Sb in soil samples. The use of this microspectrometer allows the examination of the spectral range between 190 and 220 nm where the continuum background emission of the plasma is low and the most intense resonance lines As 193.759; 197.262 nm and Sb 206.833; 217.581 nm are located. The method involves microwave-assisted digestion of samples in aqua regia, prereduction of As(V) and Sb(V) to their (+3) species with 0.3% L-cysteine by heating in a boiling water bath at 90 ± 5 °C and hydride generation in 0.01 mol L−1 HCl (pH = 2.00 ± 0.01) medium with 0.5% NaBH4 solution. The method was optimized in order to provide the simultaneous determination of As and Sb. The figures of merit were evaluated at different emission wavelengths under the optimum conditions of plasma microtorch operation (10 W, 150 mL min−1 Ar), and the best performances were obtained at 193.759 nm (As) and 217.581 nm (Sb). The figures of merit of the method were compared to those of the traditional hydride generation inductively coupled plasma optical emission spectrometry taken as a reference method. Analysis of CRMs revealed recoveries of 101 ± 9% As and 102 ± 3% Sb comparable to 102 ± 7% As and 98 ± 4% Sb in the reference method. The precision of determinations was 2–10% for 90–210 mg kg−1 As and 40–130 mg kg−1 Sb, close to 3–8% in hydride generation inductively coupled plasma optical emission spectrometry. The Bland and Altman test performed on 10 soil samples indicated no significant difference between the results obtained by the two methods, so that the miniature analytical system could be successfully applied for As and Sb monitoring in environmental samples. The proposed method is attractive in terms of analytical costs due to limited consumption of high purity HCl, power and Ar to sustain the plasma, and therefore more advantageous than hydride generation inductively coupled plasma optical emission spectrometry.

Characterization and assessment of potential environmental risk of tailings stored in seven impoundments in the Aries river basin, Western Romania

BackgroundThe objective of this study was to examine the potential environmental risk of tailings resulted after precious and base metal ores processing, stored in seven impoundments located in the Aries river basin, Romania. The tailings were characterized by mineralogical and elemental composition, contamination indices, acid rock drainage generation potential and water leachability of hazardous/priority hazardous metals and ions. Multivariate statistical methods were used for data interpretation.ResultsTailings were found to be highly contaminated with several hazardous/priority hazardous metals (As, Cu, Cd, Pb), and pose potential contamination risk for soil, sediments, surface and groundwater. Two out of the seven studied impoundments does not satisfy the criteria required for inert wastes, shows acid rock drainage potential and thus can contaminate the surface and groundwater. Three impoundments were found to be highly contaminated with As, Pb and Cd, two with As and other two with Cu. The tailings impoundments were grouped based on the enrichment factor, geoaccumulation index, contamination factor and contamination degree of 7 hazardous/priority hazardous metals (As, Cd, Cr, Cu, Ni, Pb, Zn) considered typical for the studied tailings. Principal component analysis showed that 47% of the elemental variability was attributable to alkaline silicate rocks, 31% to acidic S-containing minerals, 12% to carbonate minerals and 5% to biogenic elements. Leachability of metals and ions was ascribed in proportion of 61% to silicates, 11% to acidic minerals and 6% to the organic matter. A variability of 18% was attributed to leachability of biogenic elements (Na, K, Cl-, NO3-) with no potential environmental risk. Pattern recognition by agglomerative hierarchical clustering emphasized the grouping of impoundments in agreement with their contamination degree and acid rock drainage generation potential.ConclusionsTailings stored in the studied impoundments were found to be contaminated with some hazardous/ priority hazardous metals, fluoride and sulphate and thus presents different contamination risk for the environment. A long term monitoring program of these tailings impoundments and the expansion of the ecologization measures in the area is required.

Characterisation of soil quality and mobility of Cd, Cu, Pb and Zn in the Baia Mare area Northwest Romania following the historical pollution

The paper presents a characterisation of the soil quality and mobility of Cd, Cu, Pb and Zn in the Baia Mare city, northwest Romania, historically polluted with airborne particulate matter resulted from non-ferrous ores processing. Although the impact of the ores smelters on the environment is relatively limited today, Baia Mare is still a highly polluted site with Cd, Pb, Cu and Zn. The concentration ranges of metals in soil were (mg kg−1): 1.9-25.4 Cd, 87.7-9880 Pb, 78.3-962 Cu, 109-11500 Zn, of which in (%): 1.3-80; 2.2-40; 2.0-34 and 0.3-21 as mobile species in 0.005 mol L−1 diethylenetriaminepentaacetic acid (DTPA). Baia Mare is more polluted with Cu, Pb and Zn than Copsa Mica and Cu, Pb than Zlatna, other smelter centres in Romania. Also, pollution is higher compared to similar centres in Europe. Cd, Pb and Cu are the most severe contaminants as available species for plants and should be considered in the soil remediation strategy. The PCA on metal contents following aqua regia mineralisation and DTPA extraction allowed the identification of anthropogenic origin from three sources associated with the Flotation Station (residual species), Cuprom plant (Cu, Cd and Zn mobile species) and Romplumb plant (Pb mobile species). The car traffic as anthropogenic source does not modify the pollution pattern caused by industrial activity since no association between Pb and Zn was found. On the other hand, an affinity between Cd and Zn as well as between Cu and Pb were also identified. A particular case is that of Cu, for which the PCA revealed an interference of polluters. Statistics are in agreement with the distribution maps of contaminants.

Study of partitioning and dynamics of metals in contaminated soil using modified four-step BCR sequential extraction procedure

The modified four-step BCR sequential extraction procedure (exchangeable and weak acid available species, reducible, oxidisable and residual fractions) was used to examine the distribution of As, Cd, Cr, Cu, Pb, and Zn with soil depth in an area (Baia Mare — Bozanta, Romania) with both high natural level of elements considered as toxic and historical pollution resulting from nonferrous metallurgy. The BCR approach proved a high metal input of anthropogenic origin down to 40 cm, while at lower depths the naturally elevated metal content must be considered. Results of the partitioning study and XRD analysis of solid matrix showed the greatest potential for chemical remobilisation of Cd, Zn, and Cu in weak acidic medium as well as their affinity for the oxidisable fraction (organic matter/sulphide). The tendency of Cr, Pb, and As to be immobilised as residual or reducible species on Fe-Mn oxides was evident. Although the partitioning of As in chemically inactive forms such as scorodite (FeAsO4 · 2H2O) soluble under reducible conditions and beudantite (PbFe3(AsO4)(SO4)(OH)2)), a residual species soluble in acid media, chemical mobilisation from soil in groundwater was confirmed. Dynamic processes of metal retention in soil under different conditions, namely acidic, reducing or oxidisable, were predicted from the Pearsonșs correlation analysis of element species with soil characteristics and components such as Fe, Mn, organic matter content, pH, and total element content, respectively. At the moment of the study, soil and groundwater in the area were found to be polluted with As, Cd, Cu, Pb and Zn.

Analytical characterization of a method for mercury determination in food using cold vapour capacitively coupled plasma microtorch optical emission spectrometry – compliance with European legislation requirements

This paper presents the analytical characterization of a highly sensitive and inexpensive method for Hg determination in food based on cold vapour capacitively coupled plasma microtorch optical emission spectrometry. The novelty of the work lies in combining the on-line preconcentration of Hg cold vapour on a gold filament microcollector with a low-power (20 W) and low Ar consumption (200 mL min−1) microtorch to increase the sensitivity of the method. The method involves microwave assisted digestion of the lyophilized samples in a HNO3–H2O2 mixture, conventional chemical cold vapour generation using the SnCl2–HCl system, on-line preconcentration on a gold filament and emission measurement at 253.652 nm using a low-resolution microspectrometer. The figures of merit were discussed in relation with the demands in the Decisions 2007/333/EC, 2011/836/EC and 2002/657/EC on the determination of toxic elements in food. The detection and quantification limits were 0.005 μg kg−1 and 0.015 μg kg−1 allowing the use of the method for Hg determination in foods such as chicken meat, bread, rice, vegetables and fruits. For concentrations in the range 0.57–25.2 μg kg−1 the precision was 0.7–9.0%, below the maximum standard uncertainty set in the above mentioned legislation. Recovery of 97.9 ± 4.6% and trueness in the range (−7.7)–(+4.7%) in the analysis of five certified reference materials were found to be satisfactory, since the found concentrations fall within the ±10% bound of the target value. The proposed method developed using miniaturized instrumentation is cost-effective and enables us to achieve Hg determination in food complying with European legislation. The system has analytical potential for the future and prototyping perspectives.

A miniaturized capacitively coupled plasma microtorch optical emission spectrometer and a Rh coiled-filament as small-sized electrothermal vaporization device for simultaneous determination of volatile elements from liquid microsamples: Spectral and analytical characterization

A low power and low argon consumption (13.56 MHz, 15 W, 150 ml min(-1)) capacitively coupled plasma microtorch interfaced with a low-resolution microspectrometer and a small-sized electrothermal vaporization Rh coiled-filament as liquid microsample introduction device into the plasma was investigated for the simultaneous determination of several volatile elements of interest for environment. Constructive details, spectral and analytical characteristics, and optimum operating conditions of the laboratory equipment for the simultaneous determination of Ag, Cd, Cu, Pb and Zn requiring low vaporization power are provided. The method involves drying of 10 μl sample at 100°C, vaporization at 1500°C and emission measurement by capture of 20 successive spectral episodes each at an integration time of 500 ms. Experiments showed that emission of elements and plasma background were disturbed by the presence of complex matrix and hot Ar flow transporting the microsample into plasma. The emission spectrum of elements is simple, dominated by the resonance lines. The analytical system provided detection limits in the ng ml(-1) range: 0.5(Ag); 1.5(Cd); 5.6(Cu); 20(Pb) and 3(Zn) and absolute detection limits of the order of pg: 5(Ag); 15(Cd); 56(Cu); 200(Pb) and 30(Zn). It was demonstrated the utility and capability of the miniaturized analytical system in the simultaneous determination of elements in soil and water sediment using the standard addition method to compensate for the non-spectral effects of alkali and earth alkaline elements. The analysis of eight certified reference materials exhibited reliable results with recovery in the range of 95-108% and precision of 0.5-9.0% for the five examined elements. The proposed miniaturized analytical system is attractive due to the simple construction of the electrothermal vaporization device and microtorch, low costs associated to plasma generation, high analytical sensitivity and easy-to-run for simultaneous multielemental analysis of liquid microsamples.