Eugen Darvasi

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.

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.

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.

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.

Sono-induced cold vapour generation interfaced with capacitively coupled plasma microtorch optical emission spectrometry: analytical characterization and comparison with atomic fluorescence spectrometry

Sono-induced cold vapour generation in 0.2 mol L−1 formic acid has been interfaced for the first time with a low power (10 W) and low argon consumption (100 mL min−1) capacitively coupled plasma microtorch for mercury determination by optical emission using a low resolution microspectrometer. The method meets the requirements of green analytical chemistry in terms of the derivatisation method, cost-effective conditions for plasma generation and miniaturized instrumentation. The method is based on sample ultrasonication in a batch reactor, purging of mercury vapour, moisture removal from vapour in a Nafion tubing, Hg preconcentration on a gold filament microcollector, thermal desorption and introduction of mercury vapour into plasma via an Ar stream. Emission episode spectra of Hg were recorded at 253.652 nm. Under the optimized conditions, a detection limit of 5.0 ± 0.3 ng L−1 was found, which was better than the 12 ng L−1 obtained by atomic fluorescence spectrometry after chemical cold vapour generation with SnCl2. The analytical capability of the new method was demonstrated by analysing the certified reference materials and real samples of fish tissue, soil and sediment mineralized in an acidic mixture. The method is highly sensitive and the matrix effects associated with cold vapour generation were avoided by sample dilution. Mercury was determined using external calibration with recovery and precision in the range of 96.3–104.5% and 0.8–7%, respectively. No systematic error against atomic fluorescence with chemical cold vapour generation using SnCl2 was observed.

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.

Evaluation of figures of merit for Zn determination in environmental and biological samples using EDL excited AFS in a new radiofrequency capacitively coupled plasma

A new atomic fluorescence spectrometry system based on medium power single ring electrode radiofrequency capacitively coupled plasma torch (SRTr.f.CCP) (275 W; 27.12 MHz; 0.7 L min−1 Ar) and electrodeless discharge lamp (EDL) was assessed for Zn determination in environmental and biological samples. The EDL-SRTr.f.CCP-AFS method is virtually free from non-spectral interferences and provides a detection limit of 8.2 μg L−1 and 0.8–2.8 mg Kg−1 Zn in liquid and solid samples, respectively. The accuracy and precision of the method were assessed by Zn determination in various certified reference materials. For concentration levels of 59–11400 μg L−1 in water and 17–316 mg Kg−1 in solid sample a relative standard deviation of 1.0–10.0% and recovery of 103 ± 9% were obtained. The new spectrometric system fulfils the requirements for Zn determination in environmental and biological matrices with the advantage of an easy operation and low running costs compared to ICP-MS.