Emil A. Cordos

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).

Flame atomic emission determination of rubidium in mineral and well waters using methane-air flame as excitation source.

The rubidium content of some well and mineral waters has been determined by flame atomic emission spectrometry using the methane-air flame. Effects of the flame and of instrumental parameters (flame composition, the observation height, spectral bandpass of the monochromator) on the emission of rubidium in methane-air flame was studied and optimized. The best results were obtained using the 780.0 nm rubidium line at the observation height of 11 mm, with the flame composition of 1.12 (relative stoichiometric units, RSU) and the slitwidth of 0.6 mm. The effect of Na, K, Ca and Mg on the emission of rubidium was studied too. The detection limit of 2.3+/-0.9 mug l(-1) was obtained, in the presence of 200 mg l(-1) Cs, at a significance level of 0.05, using the two-step Neyman-Pearson criterion. The rubidium content of waters has been determined directly using both external calibration curve and standard addition method. With background correction results agree between these two methods.

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 .

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.

Methane and Carbon Monoxide Gas Detection system based on semiconductor sensor

One of the most important actual problems in the gas detection field is that there are strong demands for gas methane leak detection and CO (carbon monoxide) detection to prevent explosions or CO poisoning accidents. In this sense, the present paper describes technical characteristics, test results, and a concluding application for methane and carbon monoxide based gas detection using a sensor which can detect both CO and methane with a single sensing element. The paper presents the detection method as well as the apparatus functional sketch

Preliminary investigation of a medium power argon radiofrequency capacitively coupled plasma as atomization cell in atomic fluorescence spectrometry of cadmium

The single ring electrode radiofrequency capacitively coupled plasma torch (SRTr.f.CCP) operated at 275W, 27.12 MHz and Ar flow rate below 0.7 lmin(-1) was investigated for the first time as atomization cell in atomic fluorescence spectrometry (AFS) using electrodeless discharge lamps (EDL) as primary radiation source and charged coupled devices as detector. The signal to background ratio (SBR) and limit of detection for Cd determination by EDL-SRTr.f.CCP-AFS were compared to those obtained in atomic emission spectrometry using the same plasma torch. The detection limit in fluorescence was 4.3 ngml(-1) Cd compared to 65 ngml(-1) and 40 ngml(-1) reported in r.f.CCP-atomic emission (AES) equipped with single or double ring electrode. The lower detection limit in EDL-SRTr.f.CCP-AFS is due to a much better SBR in fluorescence. The limit of detection was also compared to those in atomic fluorescence with inductively coupled plasma (0.4 ngml(-1)), microwave plasma torch (0.25 ngml(-1)) and air-acetylene flame (8 ngml(-1)). The influence of light-scattering through the plasma and the secondary reflection of the primary radiation on the wall of the quartz tube on the analytical performance are discussed. The non-spectral matrix effects of Ca, Mg and easily ionized elements are much lower in EDL-SRTr.f.CCP-AFS compared to SRTr.f.CCP-AES. The new technique was applied in the determination of Cd in contaminated soils, industrial hazardous waste (0.4-370 mgkg(-1)) and water (113 microgl(-1)) with repeatability of 4-8% and reproducibility in the range of 5-12%, similar to those in ICP-AES. The results were checked by the analysis of a soil and water CRM with a recovery degree of 97+/-9% and 98+/-4%, for a confidence limit of 95%. The present EDL-SRTr.f.CCP-AFS is a promising technique for Cd determination in environmental samples.

Analytical characterisation of a capacitively coupled plasma torch with a central tube electrode.

A new type of radiofrequency capacitively coupled plasma torch is presented. The torch electrode geometry is coaxial with a tubular central electrode and one or two outer ring electrodes. The argon plasma is generated at 275 W radiofrequency power and 27.12 MHz and it has a very good stability and a low gas consumption of 0.4 l min(-1). The nebulized sample is introduced through the tubular electrode into the core of the annular shaped plasma thus achieving a better atomisation and a lower background. The limits of detection for 20 elements are in the range of ng ml(-1) and the dynamic range between 2.5 and 3.5. The best results are obtained with the torch with two outer ring electrodes.

Validation of the Tessier scheme for speciation of metals in soil using the Bland and Altman test

The Tessier extraction method was used for speciation of Cu, Pb, Zn, As, Fe and Mn in a large concentration range in contaminated soil with various mineralogical compositions. The results were compared by X-ray fluorescence spectrometry (XRF) as a reference method using the Bland and Altman test. A sum of five fractions (exchangeable, bound to carbonates, Fe-Mn oxides, organic matter and residual forms) was compared with the total content determined on solid matrix by the reference method. A good agreement between the methods in the whole concentration range was found for Cu, Zn, As, and Fe. For Mn and Pb, XRF was found suitable to verify the sequential extraction only for concentrations above 250 mg kg−1. This was a consequence of a poorer reproducibility of Pb extraction using the Tessier scheme due to a great difference in the mineralogical composition and the diversity of the Pb species identified in soil. The poorer result of Mn was attributed to the spectral interference of Fe in XRF.

Analytical capability of a medium power capacitively coupled plasma for the multielemental determination in multimineral/multivitamin preparations by atomic emission spectrometry

A method for multielemental (Ca, Cr, Cu, Fe, K, Mg, Mn, Na, P and Zn) determination in multimineral/multivitamins by atomic emission spectrometry in a medium power radiofrequency capacitively coupled plasma (275 W) and low Ar consumption (0.4 L min(-1)) is proposed. Determinations were performed on commercially available tablets and a standard reference material after acidic high-pressure microwave assisted digestion and using the standard additions procedure. The detection limits (mg g(-1)) were in the range 0.003 (Na)-1.5 (P) and were not depreciated by the non-spectral interference of mineral matrices of K, Ca, Mg and Na excepting Zn and P. Found concentrations corresponded generally to the labelled contents with recovery in the range of 90-107% and 1.0-13.0% repeatability. The proposed technique could be an advantageous alternative to the more expensive inductively coupled plasma atomic emission spectrometry in the quality control of multimineral/multivitamin preparations.