Dielectric Barrier Discharge Atomizer Research Articles

Next generation of dielectric barrier discharge hydride atomizers for atomic absorption spectrometry: A case study on Pb, Bi, Se and Te

The performance of hydride atomizers based on dielectric barrier discharge (DBD) was evaluated by atomic absorption spectrometry as a detector employing Pb, Bi, Se and Te as model analytes. Two designs of DBD atomizers either with glued or sputtered electrodes were investigated in combination with sinusoidal or square-wave modulated high voltage power supply sources. Moreover, the effect of gas phase dryers on analyte response was studied. Nafion tubes were found as universal dryers capable of efficient water vapor removal with no losses of analyte. Sensitivity was compared among individual DBD configurations being related also to conventional externally heated quartz tube (multi)atomizers (MM)QTA. For Te and Se comparable sensitivities were reached in all configurations of DBD atomizers and MMQTA. On the contrary, QTA provided three times higher sensitivity for Bi and Pb than DBD atomizers. Sensitivity reached among DBD atomizers was the same regardless of their electrode design and high voltage waveform modulation for Se, Te and Bi. Differences in sensitivity were observed for Pb depending on DBD atomizer configuration. Here the best sensitivity was found in DBD with sputtered electrodes coupled to power source with square-wave modulation of high voltage. It was twice higher than that reached in the DBD atomizer with glued electrodes powered by sine-wave voltage. The sensitivity in DBD atomizers correlates negatively with the amount of analyte deposited in the atomizer during atomization. >90% of Bi and Pb introduced into the system is deposited while the deposited fraction of Te and Se, respectively, decreases to 60% and 35%.

Atomization of As and Se volatile species in a dielectric barrier discharge atomizer after hydride generation: Fate of analyte studied by selected ion flow tube mass spectrometry

Atomization of hydrides and their methylated analogues in a dielectric barrier discharge (DBD) plasma atomizer was investigated. Selected ion flow tube mass spectrometry (SIFT-MS) was chosen as a detector being capable of selective detection of non-atomized original volatile species allowing thus direct quantification of atomization efficiency. Selenium hydride (SeH2) and three volatile arsenic species, namely arsenic hydride (AsH3), monomethylarsane (CH3AsH2) and dimethylarsane ((CH3)2AsH), were selected as model analytes. The mechanistic study performed contributes to understanding of the atomization processes in atomic absorption spectrometry (AAS). The presented results are compatible with a complete atomization of arsenic hydride as well as its methylated analogues and with atomization efficiency of SeH2 below 80%. Using AsH3 as a model analyte and a combination of AAS and SIFT-MS detectors has revealed that the hydride is not atomized, but decomposed in the DBD atomizer in absence of hydrogen fraction in the carrier gas. Apart from investigation of analyte atomization, the SIFT-MS detector is capable of quantitative determination of water vapor content being either transported to, or produced in the atomizer. This information is crucial especially in the case of the low-power/temperature DBD atomizer since its performance is sensitive to the amount of water vapor introduced into the plasma.

Generation of tellurium hydride and its atomization in a dielectric barrier discharge for atomic absorption spectrometry

Atomization of tellurium hydride in a dielectric barrier discharge (DBD) atomizer was investigated for the first time. First, the conditions of hydride generation were optimized with the use of a miniature diffusion flame atomizer and high-resolution continuum source atomic absorption spectrometry. Generation efficiency of more than 90% was determined from a comparison of the response to solution nebulization with inductively coupled plasma mass spectrometry. Subsequently, atomization of tellurium hydride in a plane-parallel configuration of the DBD atomizer was optimized. Argon was found as the best carrier gas under a flow rate of 75 mL min−1 while the peak-to-peak high voltage was 18 kV. A limit of detection of 56 ng L−1 (3σ, n = 15) and repeatability (RSD) of 2.8% at 5 μg L−1 were reached. The accuracy and applicability of this methodology was verified by analysis of water Standard Reference Material NIST 1643f and two model samples of tap and stream water. Laser-induced fluorescence was employed to investigate a spatial distribution of free Te atoms and to estimate atomization efficiency in the DBD. Significant fractions of free Te atoms were identified all over the length of the optical tube of the DBD atomizer covered by the electrodes and atomization efficiency of up to 100% was quantified. A feasibility of tellurium hydride in-situ collection in the DBD atomizer was studied and collection efficiency of around 50% was found promising for further studies.

Atomization of lead hydride in a dielectric barrier discharge atomizer: Optimized for atomic absorption spectrometry and studied by laser-induced fluorescence

Atomization of lead hydride in a plane-parallel volume dielectric barrier discharge (DBD) atomizer coupled to a high voltage power supply source with sinusoidal waveform (28.5 kHz) was optimized with detection by atomic absorption spectrometry. Argon was found as the best discharge gas under a flow rate of 175 mL min−1 while the DBD optimum peak-to-peak high voltage was 25 kV. The performance of the novel DBD atomizer was compared to that of a conventional externally heated quartz tube atomizer (QTA) operating at 900 °C and 100 mL min−1 Ar carrier gas flow rate. Sensitivity and limit of detection (LOD) in QTA reached 0.21 s ng−1 Pb and 0.6 ng mL−1 Pb, respectively, while they reached 0.04 s ng−1 Pb and 2.3 ng mL−1 Pb in DBD. Laser-induced fluorescence (LIF) was employed to investigate the spatial distribution of free Pb atoms as well as to quantify lead hydride atomization efficiency in both atomizers. Free Pb atoms were present only in a central region of DBD atomizer. Atomization efficiency of lead hydride was quantified by LIF to be 23 ± 7%. On the contrary, free Pb atoms were distributed homogeneously along the whole optical arm in the QTA with atomization efficiency reaching 88 ± 18%.

Influences of voltage shape and discharge gas on the temporally and spatially resolved emission characteristics of tin in a planar dielectric barrier discharge

Choosing a suitable power supply concerning the shape of the excitation voltage and the type of discharge gas for elemental analysis with a dielectric barrier discharge is not trivial. Both significantly affect the analyte signal. By means of conventional methods such as inductively coupled plasma mass spectrometry or atomic absorption spectrometry optimal conditions can be found, however the reason why the specific parameter set results in ideal signals is hidden in the detailed characteristics of the DBD. These phenomena occur on a narrow time scale of nanoseconds to microseconds and are challenging to observe. Therefore, the emission profiles of tin in a planar dielectric barrier discharge atomizer were studied by means of temporally and spatially resolved optical emission spectroscopy by varying the type of discharge gas and the shape of the excitation voltage. The latter was realized by applying either a sinusoidal or a square wave power supply. The temporally resolved emission profile showed that in case of sinusoidal excitation the power is distributed over a longer time in several discharge events, whereas with square wave excitation the power is coupled to the dielectric barrier discharge in one intensive pulse. The spatially resolved emission signals indicated a different point of excitation of Sn within the dielectric barrier discharge for each power source. The Sn emission in a plasma, which was sustained by the square wave power supply, was not significantly influenced by the change of the discharge gas from argon to helium. However, for the emission signal in a plasma excited by the sinusoidal power supply, helium had an adverse effect.

Hydride generation atomic absorption spectrometry with a dielectric barrier discharge atomizer: Method optimization and evaluation of analytical performance for tin

Atomization conditions for tin hydride in the planar dielectric barrier discharge (DBD) plasma atomizer were optimized with detection by atomic absorption spectrometry (AAS). The effects of apparatus arrangement such as the shape of a waveform function of the high voltage power supply source, DBD atomizer design as well as presence of a dryer tube filled with NaOH pellets to prevent residual aerosol and moisture transport into the DBD were investigated in detail. The optimal experimental setup consisted of a square wave high voltage power supply source coupled to a DBD with vapor-deposited electrodes in the presence of NaOH dryer upstream the DBD atomizer. Argon was found as the best discharge gas under a flow rate of 120 mL min−1 while the DBD optimum high voltage supply rate was 7 kV. A sensitivity of 0.05 s ng−1 Sn and a limit of detection of 1.1 ng mL−1 Sn were reached under optimized conditions. Optimization of the whole experimental setup resulted in 7-fold improvement of sensitivity compared to the original arrangement consisting of a sinusoidal source coupled to a DBD atomizer with glued electrodes in absence of the dryer. The analytical performance of the DBD atomizer under optimized conditions was compared to that of a commonly used externally heated quartz tube atomizer.

Behavior of selenium hydride in heated quartz tube and dielectric barrier discharge atomizers

Atomization of SeH2 in an externally heated multiple microflame quartz tube atomizer (MMQTA) as well as planar dielectric barrier discharge (DBD) atomizer was investigated using a variety of probes. Deposits of Se on inner surfaces of the atomizers were quantified and their distribution visualized by autoradiography with 75Se radiotracer. The gas phase fraction of Se transported beyond the confines of the atomizers was also determined. In the MMQTA, a 15% mass fraction of Se was deposited in a narrow zone at both colder ends of the optical arm (100–400 °C). By contrast, a 25-40% mass fraction of Se was deposited homogeneously along the entire length of the optical arm of the DBD, depending on detection technique employed. The fraction of Se transported outside the MMQTA approached 90%, whereas it was 50–70% in the DBD. The presence of H2 was essential for atomization of selenium hydride in both atomizers. The gaseous effluent arising from the hydride generator as well as the atomizers was investigated by direct analysis in real time (DART) coupled to an Orbitrap-mass spectrometer, enabling identification of major gas phase species of Se.

Dielectric barrier discharge induced atomization of gaseous methylethylmercury after NaBEt4 derivatization with purge and trap preconcentration for methylmercury determination in seawater by GC-AFS

A novel method suitable for methylmercury (CH3Hg) analysis in seawater by gas chromatography (GC)-atomic fluorescence spectrometry (AFS) based on dielectric barrier discharge (DBD) induced atomization of gaseous methylethylmercury (CH3HgC2H5) after sodium tetraethylborate (NaBEt4) derivatization with purge and trap preconcentration was developed in this work. In the proposed method, with NaBEt4 used as derivatization reagent, the nonvolatile CH3Hg could be converted to the gaseous CH3HgC2H5 and trapped in a quartz tube with Tenax sorbent for preconcentration. A DBD atomizer was employed for the atomization of CH3HgC2H5 to Hg0 between the GC separation and AFS detection instead of the conventional thermal decomposition atomizer, which had not been reported before. The DBD atomizer not only produces a comparable atomization efficiency for CH3HgC2H5 to the thermal decomposition atomizer, but also can be operated at room temperature with low power consumption (5 W). The effects of DBD input discharge voltage, DBD discharge distance, N2 gas purge time, and thermal desorption time on CH3Hg determination were evaluated. The method provided good reproducibility (RSD, 2.0%) and low detection limits of CH3Hg (LOD, 0.0008 ng L−1). The proposed method was validated by the analysis of a certified reference material (GBW08675) and successfully applied to the determination of CH3Hg in sub ng L−1 level in different seawater samples.

Trace determination of antimony by hydride generation atomic absorption spectrometry with analyte preconcentration/atomization in a dielectric barrier discharge atomizer

Atomization conditions for antimony hydride in the plasma atomizer based on a dielectric barrier discharge (DBD) with atomic absorption spectrometric detection were optimized. Argon was found as the best discharge gas under a flow rate of 50 mL min− 1 while the DBD power was optimum at 30 W. Analytical figures of merit including interference study of As, Se and Bi have been subsequently investigated and the results compared to those found in an externally heated quartz tube atomizer (QTA). The limit of detection (LOD) reached in DBD (0.15 ng mL−1 Sb) is comparable to that observed in QTA (0.14 ng mL−1 Sb). Finally, possibility of Sb preconcentration by stibane in situ trapping in a DBD atomizer was studied. For trapping time of 300 s, the preconcentration efficiency and LOD, respectively, were 103 ± 2% and 0.02 ng mL−1.

Preconcentration and Atomization of Arsane in a Dielectric Barrier Discharge with Detection by Atomic Absorption Spectrometry.

Atomization of arsane in a 17 W planar quartz dielectric barrier discharge (DBD) atomizer was optimized, and its performance was compared to that of a multiple microflame quartz tube atomizer (MMQTA) for atomic absorption spectrometry (AAS). Argon, at a flow rate of 60 mL min(-1), was the best DBD discharge gas. Free As atoms were also observed in the DBD with nitrogen, hydrogen, and helium discharge gases but not in air. A dryer tube filled with NaOH beads placed downstream from the gas-liquid separator to prevent residual aerosol and moisture transport to the atomizer was found to improve the response by 25%. Analytical figures of merit were comparable, reaching an identical sensitivity of 0.48 s ng (-1) As in both atomizers and limits of detection (LOD) of 0.15 ng mL(-1) As in MMQTA and 0.16 ng mL(-1) As in DBD, respectively. Compared to MMQTA, DBD provided 1 order of magnitude better resistance to interference from other hydride-forming elements (Sb, Se, and Bi). Atomization efficiency in DBD was estimated to be 100% of that reached in the MMQTA. A simple procedure of lossless in situ preconcentration of arsane was developed. Addition of 7 mL min(-1) O2 to the Ar plasma discharge resulted in a quantitative retention of arsane in the optical arm of the DBD atomizer. Complete analyte release and atomization was reached as soon as oxygen was switched off. Preconcentration efficiency of 100% was observed, allowing a decrease of the LOD to 0.01 ng mL(-1) As employing a 300 s preconcentration period.

Atomization of Bismuthane in a Dielectric Barrier Discharge: A Mechanistic Study.

Atomization of bismuthane in a planar dielectric barrier discharge (DBD) atomizer was investigated using a variety of probes, including atomic absorption spectrometry (AAS) to monitor distribution of free atoms along the optical path and direct analysis in real time (DART) coupled to an Orbitrap mass spectrometer to identify the structure of the species arising from the hydride generator as well as the atomizer. Results obtained with the DBD were compared to those from a conventional externally heated quartz tube atomizer (QTA). Free Bi atoms were essentially absent outside the central part of the DBD atomizer, suggesting their high reactivity. The gas phase analyte fraction transported beyond the confines of the DBD or QTA atomizers, quantified by inductively coupled plasma mass spectrometry (ICP-MS), was less than 10%. The amount of Bi found in acidic leachates of the interiors of both atomizers, representing the fraction retained on their surfaces, was ca. 90%. These complementary experiments comprising the determination of recovered Bi in the nitric acid leachates from deposition in the atomizer on the one hand and quantification of the Bi fraction transportable outside the atomizer on the other, were in excellent agreement, providing 100% mass balance of detected analyte. The high fraction of Bi deposited in the atomizers indicates significant reactivity of free Bi atoms, which is in accord with the fact that almost no free Bi atoms exist beyond the physical boundaries of the DBD. The extent of interference from other hydride forming elements (As, Sb, Se) on Bi response by AAS using DBD and QTA atomizers was investigated, with the former atomizer providing superior performance. Compared to QTA, DBD provided 2 orders of magnitude and 1 order of magnitude, respectively, better resistance to interference from Se and Sb.

Determination of bismuth by dielectric barrier discharge atomic absorption spectrometry coupled with hydride generation: method optimization and evaluation of analytical performance.

Atomization of bismuth hydride in a 17 W planar quartz dielectric barrier discharge (DBD) atomizer was optimized and the performance of this device compared to that of a conventional quartz tube atomizer (QTA) for atomic absorption spectrometry (AAS). Modification of the inner surface of the DBD atomizer using dimethyldichlorsilane (DMDCS) was essential since it improved sensitivity by a factor of 2-4. Argon, at a flow rate of 125 mL min(-1), was the best DBD discharge gas. Free Bi atoms were also observed in the DBD with nitrogen, hydrogen, and helium discharge gases but not in air. The detection limit for Bi (1.1 ng mL(-1)) is worse than with the QTA (0.16 ng mL(-1) Bi). A poorer detection limit compared to a QTA is a consequence of the shorter optical path of the DBD. Moreover, the lower atomization efficiency and/or faster decay of free atoms in the DBD has to be considered. The performance of the DBD as an atomizer reflects both effects, i.e., atomization efficiency and free atom decay, was estimated to be 65% of that of the externally heated quartz tube atomizer. Nevertheless, this hydride generation DBD-AAS approach can be used for the routine determination of Bi, providing repeatability and accuracy comparable to that reached with a QTA, as demonstrated by analysis of NIST SRM 1643e (trace elements in water). The potential of in-atomizer preconcentration in a DBD atomizer is outlined.

Computational Modelling of the Volatile Hydride Fragmentation in a Dielectric Barrier Discharge Atomizer

In this study, we present a model whereby a fragmentation of arsenic hydride in a rectangular dielectric barrier discharge (DBD) atomizer is investigated. The aim is to elucidate the distribution of the intermediates species and generated free analyte atoms along atomizer channel, which is required to decide the optimal position for spectrometric data acquisition. Simulation results indicate that formation of intermediate species and free arsenic atoms is initiated in the first section of atomization channel before reaching the section between the electrodes. Moreover, concentration of free arsenic atoms saturates to a maximum and does not vary thereafter along atomization channel. This result could be attributed to the presence of abundance of hydrogen radicals along atomization channel which limits recombination reactions and ultimately maintains free atom life, which is so useful for analytical purposes. This outcome suggests an approach for radial data acquisition from any position along DBD atomization channel with same sensitivity. Furthermore, this result indicates that DBD atomizer is appropriate for analytical purposes and competitive to other well known atomization tools such as a quartz cell atomizer. The model has been verified experimentally upon examining arsenic and mercury qualitatively from applying chemical vapour generation techniques. Approximately similar results obtained from three radial positions along the atomization channel, whereas a significant increase in signal intensity observed when applying axial viewing by 22 and 40% for arsenic and mercury respectively. Furthermore, a quantitative determination for arsenic is also tried; however, the results were found not useful for model validation due to the hydrogen magnification effect on the recorded spectrum.

A Miniaturized Long-Optical Path Atomic Absorption Spectrometer with Dielectric Barrier Discharge as Atomizer for Mercury and Methylmercury

The development of miniaturized instrumentations for specific analytical purposes has been one of the most im- portant momentum in the field of instrumental innovation. Sequential injection system as a miniaturized analytical platform provides an alternative for field of analysis of heavy metal contaminants. It will exhibit more powerful capability with the introduction of atomization function and improvement of detection sensitivity. In this work, a miniature long-optical path atomic absorption spectrometric system is developed with dielectric barrier discharge (DBD) low temperature micro-plasma as atomizer. Mercury and methylmercury vapor is generated in a sequential injection system. It is directed to flow through a gas-liquid separator, a glass wool moisture-removal microcolumn and the DBD atomizer, and finally transported into the long optical-path detection cell for quantitative analysis by atomic absorption spectrometry. A 10 mA lamp current is used with a mercury hollow cathode lamp, and a 260 V negative high voltage for the photomultiplier is set. The detection sensitivity of the present system is highly improved by the increase of absorption optical path (1.1 mm i.d., 400 mm length), and the at- omization of hydride is completely achieved by the DBD micro-plasma atomizer. Meanwhile, a glass wool moisture-removal microcolumn integrated in the flow system effectively eliminates the influence of concomitant moisture during the vapor generation process, which avoids the drift of absorbance baseline. The absorbance arising from mercury is recorded by turn- ing off the DBD atomizer, while the total absorbance from both mercury and methylmercury is measured by turning on the DBD atomizer. Further experiments demonstrated satisfactory additivity for the absorbance arising from inorganic and methyl mercury, which provides basis for the determination of mercury and methylmercury. With a sampling volume of 1.0 mL, detection limits of 0.3 and 0.4 μgL -1 are achieved respectively for inorganic and methylmercury, along with RSD val- ues of <4%. The reliability of the present system is demonstrated by analyzing certified reference materials and real sam- ples for mercury speciation. Keywords dielectric barrier discharge; long optical-path; atomic absorption spectrometry; mercury; speciation

Simultaneous determination of arsenic and antimony by hydride generation atomic fluorescence spectrometry with dielectric barrier discharge atomizer

Simultaneous determination of As and Sb by hydride generation atomic fluorescence spectrometry was developed with the dielectric barrier discharge plasma as the hydride atomizer. The low-temperature and atmospheric-pressure micro-plasma was generated in a quartz cylindrical configuration device, which was constructed by an axial internal electrode and an outer electrode surrounding outside of the tube. The optimization of the atomizer construction and parameters for hydride generation and fluorescence detection systems were carried out. Under the optimized conditions, the detection limits for As and Sb were 0.04 and 0.05 μg L −1, respectively. In addition, the applicability of the present method was confirmed by the detection of As and Sb in reference materials of quartz sandstone (GBW07106) and argillaceous limestone (GBW07108). The present work provided a new approach to exploit the miniaturized hydride generation dielectric barrier discharge atomic fluorescence spectrometry system for simultaneous multi-element determination.

Non-chromatographic determination of inorganic and total mercury by atomic absorption spectrometry based on a dielectric barrier discharge atomizer

A novel, fast and simple non-chromatographic approach for determination of inorganic and total mercury has been developed by cold vapor atomic absorption spectrometry based on dielectric barrier discharge (DBD) atomizer. The determination of inorganic mercury and total mercury can be achieved in a fast sequential fashion (1 min sample−1). In the proposed method, with 0.01% (m/v) NaBH4 used as reductant, inorganic mercury is reduced to elemental mercury, whereas the methylmercury forms an intermediate volatile methylmercury hydride (CH3HgH). A low temperature DBD atomizer was employed for the atomization of CH3HgH. Only inorganic mercury can be measured in the absence of the DBD plasma. However, in addition to inorganic mercury, CH3HgH can be atomized and total mercury is determined in the presence of the plasma. The methylmercury concentration can then be obtained from the difference. The effects of several experimental parameters, such as NaBH4 concentration, HCl concentration, discharge gas and gas flow rate on the analytical performance were investigated. The method provided good reproducibility (<3% RSD) and the detection limits of Hg2+ and CH3Hg+ were found to be 0.35 ng mL−1 and 0.54 ng mL−1, respectively. The proposed method was validated by the analysis of a certified reference material (tuna fish). In addition, it was successfully applied to the analysis of fish samples. The method is excellent for mercury speciation measurements as it provides short analysis time and good reproducibility.

Determination of bismuth in solid samples by hydride generation atomic fluorescence spectrometry with a dielectric barrier discharge atomizer

An atmospheric pressure dielectric barrier discharge (DBD) atomizer was investigated for bismuth (Bi) determination with hydride generation (HG) atomic fluorescence spectrometry (AFS). The characteristics of the atomizer and the effects of experimental parameters, including observation height, discharge power, flow rate of discharge gas and AFS carrier gas were optimized. The linear range of present method for Bi determination is 0.5–300.0 μg L −1 with a detection limit of 0.07 μg L −1 (3 σ). The method was validated by the analysis of reference materials (GBW08517 and GSB-14) and the results agreed well with the reference values. The established method was applied to the determination of Bi in ore, soil and ash samples.

Evaluation of a hydride generation-atomic fluorescence system for the determination of arsenic using a dielectric barrier discharge atomizer

A new atomizer based on atmospheric pressure dielectric barrier discharge (DBD) plasma was specially designed for atomic fluorescence spectrometry (AFS) in order to be applied to the measurement of arsenic. The characteristics of the DBD atomizer and the effects of different parameters (power, discharge gas, gas flow rate, and KBH 4 concentration) were discussed in the paper. The DBD atomizer shows the following features: (1) low operation temperature (between 44 and 70 °C, depending on the operation conditions); (2) low power consumption; (3) operation at atmospheric pressure. The detection limit of As(III) using hydride generation (HG) with the proposed DBD-AFS was 0.04 μg L −1. The analytical results obtained by the present method for total arsenic in reference materials, orchard leaves (SRM 1571) and water samples GBW(E) 080390, agree well with the certified values. The present HG-DBD-AFS is more sensitive and reliable for the determination of arsenic. It is a very promising technique allowing for field arsenic analysis based on atomic spectrometry.

Application of atmospheric pressure dielectric barrier discharge plasma for the determination of Se, Sb and Sn with atomic absorption spectrometry

The atomization of hydride-forming elements, Se, Sb and Sn, has been studied with an atmospheric pressure dielectric barrier discharge atomizer. The elements were first converted to hydride through the reaction with NaBH 4. Then the hydride were atomized in the atomizer and detected by atomic absorption spectrometry. The effects of operational parameters such as power, gas flow rate and concentrations of HCl and NaBH 4 were investigated. Compared with other hydride atomization methods, the proposed atomizer shows the following features: (1) small size, which is preferable for the miniaturization of the total analytical system; (2) low temperature, which would be helpful for further improvement in the compactness of the total analytical system; (3) low power consumption, which is also necessary for the development of analytical instrumentation for in situ detection of environmentally important elements. The analytical performance of the atomizer has also been investigated. The detection limits of Sb, Se and Sn obtained with the present method were 13.0, 0.6 and 10.6 μg l − 1 . This detector is a very promising technique for hydride detection.

Atomization of Hydride with a Low-Temperature, Atmospheric Pressure Dielectric Barrier Discharge and Its Application to Arsenic Speciation with Atomic Absorption Spectrometry

This paper describes a novel hydride atomizer based on atmospheric pressure dielectric barrier discharge (DBD) plasma. The plasma was generated with a 3700-V, 20.3-kHz, and 5-W electrical power supply and easily sustained with inert gases (He or Ar) at a flow rate of 250 mL.min(-1) after optimization. However, it cannot be sustained with N2. This atomizer offers the advantages of low operation temperature and low power consumption in comparison with the currently used electrothermal quartz atomization operated at 900 degrees C with a power supply of several hundred watts. To confirm the utility of the proposed atomizer, four arsenic species (As(III), As(V), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA)) were determined by the present atomization technique. A hyphenation of HPLC coupled to hydride generation AAS with the optimized DBD atomizer has been successfully used for the speciation of arsenic in order to demonstrate the potential of this atomizer in the present study. The characteristics of the DBD atomizer and the effects of different parameters (discharge gas, gas flow rate, voltage, HCl concentration, KBH4 concentration) are discussed in the paper. Compared with other hydride atomization techniques, the proposed method shows the following features: (1) small size (70 mm x 15 mm x 5 mm), which is preferable for the miniaturization of the total analytical system; (2) low power consumption (< or =5 W), which indicates the possibility of the development of portable, fieldable analytical instrumentation for in situ detection using battery as power supply; (3) low atomizer temperature (approximately 70 degrees C), which is in favor of the compactness of the total instruments; (4) avoidance of residue moisture removal in comparison with the existed GD system, which leads to the facility of the system. The analytical figures of the present technique were evaluated. The detection limits of As(III), As(V), MMA, and DMA obtained with HG-DBD-AAS were 1.0, 11.8, 2.0, and 18.0 microg.L(-1), respectively. The accuracy of the system was verified by the determination of arsenic in reference material of orchard leaves SRM 1571. The concentration of As determined by the present method agreed well with the reference values. The speciation of arsenic in the freeze-dried urine SRM 2670 were carried out, and the results obtained were in agreement with the results of HPLC-ICPMS and the reported values by other laboratories.