Argon Microwave-induced Plasma Research Articles

Photochemical vapor generation combined with headspace solid phase microextraction for determining mercury species by microwave-induced plasma optical emission spectrometry

A new and simple photochemical vapor generation (PCVG) technique utilizing UVC irradiation combined with headspace solid phase microextraction (HS SPME) is developed for the unified separation and preconcentration of mercury species followed by their determination through miniaturized thermal desorption argon microwave-induced plasma optical emission spectrometry (TD–MIP–OES). Inorganic mercury (Hg2+), methylmercury, and ethylmercury are decomposed and reduced to mercury cold vapor in 2% formic acid through combined UVC irradiation and thermochemical reduction. The mercury vapor is subsequently liberated from the liquid phase and transported to the headspace. Without any tedious sample pretreatments, HS SPME using DVB/CAR/PDMS fiber affords clean and convenient one-step extraction followed by direct desorption into the injection port of the detection system. The 15 min-long UVC irradiation, thermal reduction of mercury species, and preconcentration of mercury vapor resulted in low limits of detection between 0.08 and 0.10 ng mL−1 for all mercury species. The method performance was validated by determining the total mercury and MeHg concentration in a tuna fish certified reference material (ERM CE464) and total mercury in sediment ERM CC580, and the results agreed well with the certified values.

Efficient degradation of Fipronil in water by microwave-induced argon plasma: Mechanism and degradation pathways

Fipronil and its metabolites are potentially harmful to the ecological environment and have chronic neurotoxic effects, which makes it to be classified as class C carcinogens. Fipronil has been banned from agricultural use in China since 2009, but its residue remains in the environment. Therefore, an efficient and economical method is urgently needed to degrade fipronil residues in the environment. Herein, the degradation of fipronil in water solution using argon microwave-induced plasma (MIP) system was studied and a plausible reaction pathway was proposed in combination with Density Functional Theory (DFT) calculations. The degradation of fipronil by MIP system was optimized in terms of input power, plasma-sample distance, initial concentration and gas flow rate. After short time MIP treatment with an input power of 150W, as high as 85.62% degradation efficiency was achieved for the fipronil at concentration of 20mg·L--1 under the optimized conditions, and the corresponding energy efficiency was 1334.8mg·kwh-1. Optical emission spectrometry (OES) was employed to characterize the distribution and intensity of OH, H and O species which play key roles in the degradation of fipronil by plasma, and it revealed that the degradation reaction mainly occurs at gas-liquid interface where the highest intensity of OH, H and O species was observed. High resolution mass spectrometric analysis in combination quantum chemical calculations indicate that a wide diversity of reaction processes occurred for fipronil degradation under MIP treatment, involving oxidation or reduction, nitro reduction, oxidative dichlorination, reductive dichlorination, hydration, dehydration and thiourea to urea. The possible degradation mechanism and pathways were proposed based on the degrading species identified by high resolution Mass Spectrometry (HRMS) and the thermodynamic profiles.

Measuring the electron density in plasmas from the difference of Lorentzian part of the widths of two Balmer series hydrogen lines

We present an alternative optical emission spectroscopy method to measure the plasma electron density from the difference of widths of two Balmer series hydrogen lines ( H α and H β ), especially convenient for non-thermal plasmas since with this method, there is no need to know either the gas temperature or the van der Waals contribution to the Lorentzian part of the line. In this paper it has been assumed that the part of full width at half maximum due to Stark broadening can be determined with the approximation of Lorentzian line shape. The method has been applied to the determination of the electron density in an argon microwave-induced plasma maintained at atmospheric pressure, and comparison with the results obtained using other diagnostic methods has been done. • An alternative method to measure the electron density in plasmas from two Balmer series hydrogen lines ( H α and H β ) is presented. • The method is very convenient for plasmas with electron densities of the order of 10 14 cm − 3 and above, at low gas temperatures. • It has been applied to the determination of the electron density of an argon microwave plasma at atmospheric pressure. • Results from it are in good agreement with previous ones obtained using other diagnostic methods.

Study of Spectral Character of Alkali Metals Using Microwave Plasma Torch Simultaneous Spectrometer

Abstract A microwave plasma torch (MPT) simultaneous spectrometer was used to study the spectral character and the matrix effect on alkali metal ions in solution. The main parameters were optimized. The microwave forward power was 100 W. The argon flow rate that was used to sustain the Ar-MPT included the flow rate of carrier gas and the flow rate of support gas, which were 0.8 and 1.0 L/min, respectively. The HC1 concentration in the solution was 0.02 mol/L. The observation height was 9.0 mm. The detection limits of Li, Na, K, Rb, and Cs were 0.0003, 0.0004, 0.009, 0.07 and 2.4 mg/L, respectively, and the results obtained by the Ar-MPT were compared with those obtained by argon inductively coupled plasma(Ar-ICP) and argon microwave induced plasma(Ar-MIP). The interference effects of several matrix elements were also studied.

Spectroscopic characterization of low power argon microwave-induced plasma with gaseous species produced from ethanol–water solutions in continuous hydride generation process

Abstract Low power microwave-induced argon plasma generated by resonant TE 101 rectangular cavity was investigated upon introduction of volatile species formed in the reaction with sodium tetraborohydrate(III) in hydrochloric acid–ethanol solution. The molecular emission bands of OH and CH were used for rotational temperature ( T rot ) determination, while the atomic emission lines of Ar, H and Sb were applied for excitation temperature ( T exc ) measurement. Assuming a Boltzmann distribution, the temperatures were calculated with the aid of the least squares method. Electron number density ( n e ) derived from Stark broadening of the H β line was found to be between 2.5×10 15 and 0.57×10 15 cm −3 . The detection limits (DL) were determined for Hg and Sb. The influence of ethanol concentration in analyte solution and microwave power on measured parameters, was investigated. The results showed that T rot (OH) increased from 2970 to 3820 K while T rot (CH) decreased from 6100 to 4540 K with ethanol concentration in the solution, ranging from 10 to 90%. Under the same experimental conditions the excitation temperature for Ar, H and Sb varied in the following ranges: 5670–4800, 6190–3950 and 10500–7390 K, respectively. It was observed that element DL were significantly influenced by the presence of ethanol in the sample solution. The DL values for Hg and Sb were, as follows: 0.5–11 and 5.3–35 μg l −1 , respectively.

Spectroscopic study of a surface-wave-sustained argon plasma column at atmospheric pressure by means of a power interruption technique

The instantaneous response and the temporal evolution of the intensity of some atomic lines to the sudden interruption of the high frequency (HF) power maintaining the discharge have been studied in an argon microwave-induced plasma (MIP) sustained by a surface wave at atmospheric pressure. The instantaneous response permits the detection of possible departures from the Local Thermodynamic Equilibrium (LTE) existing in the steady-state discharge and confirms that these discharges behave as a two-temperature plasma, in the investigated conditions. Furthermore, this response has allowed the determination of the elementary balances controlling the excited level populations. In turn, the so-called temporal evolution of the line intensities has given additional information about the processes governing the electron losses during the extinction in this type of discharge.

Enthalpy probe diagnostics of an atmospheric pressure argon microwaveinduced plasma

An argon microwave-induced plasma (MIP) at atmospheric pressure wasgenerated in a TE10 mode waveguide. The discharge was sustained bya relatively low absorbed power of around 215 W. An enthalpy probe was used tocharacterize the argon MIP discharge, yielding values of enthalpy, velocityand heavy particle temperature along the jet axis. The theory of the enthalpyprobe operation and calibration is reviewed and the system for itsimplementation is described. The heavy particle temperature is found to beabout 1600 K and the velocity to be about 150 m s-1 at theexit plane of the discharge tube for an argon flow rate of 1.6 l min -1. Although the assumption of local thermodynamic equilibrium isrequired to determine the temperature and velocity in the jet from the enthalpyprobe measurements, it is argued that the values obtained should be reasonableeven if, as expected in MIPs, the electron temperature issignificantly higher than the heavy particle temperature.

An Improved Argon Microwave-Induced Plasma Ionization Detector for Gas Chromatography

The microwave-induced plasma ionization detector (MIPID) for gas chromatography has been improved. The effect of the structure of MIPID and experimental parameters on its performance were studied with argon as the discharge and carrier gas. The sensitivity, linear dynamic range, noise, and stability of three types of MIPIDs have been compared for various compounds. For most organic compounds, detection limits in the range 10−10–10−11g with a linear dynamic range of four to five orders of magnitude were obtained. The influence of air entrainment into the plasma on the analytical performance of the detector was also studied.

Vertically positioned axially viewed aerosol cooled plasma — a new design approach for microwave induced plasma optical spectrometry with solution nebulization

Abstract A vertically positioned axially viewed argon microwave induced plasma (Ar-MIP) system is described, which can serve as a spectrochemical excitation source. The design concept of improved TE 101 rectangular cavity based on strong coupling between the plasma load and the magnetron generator has been presented. The idea of plasma cooling with a pure water aerosol is explained. The torch cooling system which permits aerosol generation and circulation has been described in detail. The influence of cooling on the argon plasma positioning in the discharge tube was investigated. The spectroscopic temperatures of iron and argon have been measured to evaluate excitation conditions and effect of plasma cooling. Analytical performance of the presented MIP system was characterized by determination of the limits of detection for some elements and comparison with other Ar-MIP experimental setups. Analysis of certified reference material was performed to determine the accuracy and precision available with the presented system.

A possibility of element specific detection in HPLC by means of MIP-AES coupled with hydraulic high pressure nebulization.

An interface for coupling hydraulic high pressure nebulization (HHPN) with microwave induced plasma (MIP) atomic emission spectrometry (AES) is described. An appropriate spray chamber and aerosol desolvation system has been constructed for matching the HHPN generated aerosol flow with the loading capacity of toroidal argon and cylindrical helium MIP sources. The system has been optimized for aqueous solutions. Nanogram amounts of metals and nonmetals could be detected by the HHPN-MIP-AES technique developed. The HHPN devices are directly compatible with HPLC solvent flow, therefore they can be directly coupled with HPLC separations in aqueous media.

Direct coupling of high-performance liquid chromatography to microwave-induced plasma atomic emission spectrometry via volatile-species generation and its application to mercury and arsenic speciation

The on-line coupling of vesicle-mediated high-performance liquid chromatography (HPLC) to low-power argon microwave-induced plasma (MIP) detection is described. The analytical potential of such a hybrid technique is illustrated for the speciation of mercury and arsenic compounds. Continuous cold vapour (CV) or hydride generation (HG) techniques were used as interfaces between the exit of the HPLC column and the MIP, held in a surfatron at reduced pressure. Detection was by atomic emission spectrometry (AES). The effect of different surfactants on mercury CV generation was evaluated using SnCl2 as the reducing solution instead of sodium tetrahydroborate(III). Emission signals increased by about 75% by adding the vesicle-forming surfactant didodecyldimethylammonium bromide (employed as the HPLC mobile phase for speciation). Enhancements of around 100% of signals were found in micelles of cetyltrimethylammmonium bromide. The detection limits by vesicular HPLC–HG-MIP-AES for the more toxic arsenic species investigated (namely, arseneous, arsenic, monomethylarsonic and dimethylarsinic acids) were in the range 1–6 ng ml–1. The detection limits for mercury speciation by vesicular HPLC–CV-MIP-AES were 0.15 ng ml–1 Hg for inorganic mercury and 0.35 ng ml–1 Hg for methylmercury. Both methods have been successfully applied to the speciation of mercury and arsenic in natural waters (sea-water and tap water) and in human urine.

The use of optical emission spectrometry with microwave induced plasma (MIP) discharges in a surfatron combined to different types of hydride generation for the determination of arsenic

The stability and analytical figures of merit of argon microwave induced plasma (MIP) discharges in a surfatron as sources for optical emission spectrometry (OES) are described. These MIPs have been used for the determination of arsenic after hydride generation. They could cope with the excess of hydrogen developed during the hydride generation step and thus not necessitated an isolation of the hydrides before releasing them into the MIP. Two methods for the generation of the volatile AsH3 were applied. First a micro method was used with solid NaBH4 on which 10 μ1 of the acidified sample solution is transferred. Its capabilities were compared to those of continuous hydride generation using a 5% (w/w) NaBH4-solution and continuous liquid removal in a flow cell. Both methods were optimized for an argon MIP operated at a power of 120–160 W and gas flows of 20 l/h Ar. In the case of solid NaBH4 the detection limit for As has been found to be 1.0 μg/ml (10 ng) and with the flow cell hydride generation 50 ng/ml. The calibration curves are linear over three orders of magnitude. Interferences caused by Sb, Fe, Sn and NaCl were investigated. No interferences occurred for Sb up to an interferent concentration of 250 μg/ml. The presence of Fe causes a significant depression of the As signal whereas an increase of the As signal was observed in the case of Sn. High NaCl concentrations did not influence the As signals when using continuous hydride generation, but had a great influence when using solid NaBH4.

Direct solid sample analysis in a moderate-power argon microwave-induced plasma with spark generation

A spark–Ar microwave-induced plasma (MIP) atomic emission spectrometry system has been developed for the direct analysis of solid samples. Particles of the sample are generated with a spark and swept into a moderate-power Ar MIP connected to a sequential spectrometer. Low-Alloy Steel and Aluminium Alloy Standard Reference Materials were analysed by the proposed system and the detection limits for most elements of interest were around 10 µg g–1 or less, which are comparable to a spark–Ar inductively coupled plasma (ICP) system. Precisions were in the range 3–11%, which are 2–3 times higher than those of the spark–ICP system. Hence spark–MIP AES is a viable alternative technique to spark–ICP-AES.

Spectroscopic study of argon MIP discharge used for analysis of solutions

Microwave-induced plasma (MIP) is an attractive excitation source which seems to be competitive to ICP-AES discharge. Reduced requirements in power and amounts of carrier gas and solution are considerable in comparison with ICP-AES. However, some disadvantages (such as a partial atomization and instability of discharge) can arise from the reduced power. Fundamental studies of MIP could be a help for control and proper selection of operating parameters of this discharge type. The behavior of solutions sprayed into an argon plasma was studied in a commercial MIP under different experimental conditions (argon and aerosol flow rates, discharge power). Rotational and vibrational energy distributions on the basis of the OH A2Σ − X2π molecular spectra and electronic energy distributions on the basis of atomic spectra have been measured under operative conditions and discussed from the point of view of analytical applications of MIP.

A novel microwave plasma cavity assembly for atomic emission spectrometry

Abstract The design approach that leads to a simple new cavity structure for a microwave discharge used for analytical chemistry is outlined. The design and construction of a totally new and efficient microwave cavity assembly, namely an integrated microwave generator/cavity combination, operated at 2.45 GHz, and preliminary operating conditions that exceed certain operational capabilities of the existing Beenakker and surfatron arrangements are described. The feasibility of operating such a microwave plasma cavity arrangement to form plasma discharges in argon, helium, nitrogen, air and oxygen at atmospheric pressure for atomic emission spectrometry has been demonstrated. The generation of an oxygen microwave induced plasma (MIP) discharge with conventional tubes used routinely in the argon or helium MIP suggests its application in spectrochemical analysis. The introduction of wet aerosols, because of the excellent resistance to detuning caused by changes in plasma density, can be accomplished by using direct solution nebulization with no desolvation system and with a typical inductively coupled plasma nebulizer-spray chamber.

Chemical generation of chlorine, bromine and iodine for sample introduction into a surfatron-generated argon microwave-induced plasma

A new analytical method that combines on-line gas generation and MIP-Surfatron for example introduction and analysis is reported. Chlorine, bromine, and lodine are generated continually from aqueous solutions by using a lead (IV) oxide minicolumn connected to the plasma excitation source via a gas-liquid separator. this permits introduction of the vaporized sample directly into the plasma by using the support gas flow as analyte carrier gas

Study of a toroidal argon MIP and a cylindrical helium MIP for atomic emission spectrometry—II: Combination with graphite furnace vaporization and use for analysis of biological samples

The capabilities of a toroidal argon and a diffuse helium microwave induced plasma (MIP) operated in a TM 010 resonator and in combination with electrothermal vaporization have been studied for atomic emission spectrometry (AES). The 75 W toroidal MIP has been found to improve the power of detection with respect to the filament argon MIP by a factor of 3–10. The detection limits using 50 μl solution aliquots for a large series of elements are between 0.1 and 100 ng ml . With a diffuse helium MIP in combination with graphite furnace vaporization the detection limit for P is 10 ng ml and for Pb 1 ng ml . In the toroidal argon MIP, matrix effects due to alkali elements occur already at concentrations of 10 μg ml of Na and could not be eliminated satisfactorily by the use of NH 4 NO 3 . In. the helium MIP, also volatilization interferences in the case of Ca and P were found. After separation of the alkali elements by sorption of the trace elements as hexamethylene-dithiocarbamates (HMDC) on acetylated cellulose, MIP-AES with the toroidal argon MIP coupled to electrothermal vaporization has been found to be suitable for multielement determinations in biological samples, subsequent to wet chemical sample decomposition in closed PTFE (Teflon) vessels. This is demonstrated by the determination of Fe, Cu and Zn in the NBS standard reference materials of bovine liver, orchard leaves and tomato leaves.

Excitation temperature measurements of a pulse-operated argon microwave-induced plasma.

The present study reports time-and spatially-dependent emission intensities and corresponding excitation temperatures for a pulse-operated argon microwave-induced plasma. These measurements were made at a variety operating conditions. Excitation temperatures were determined using argon, copper, and iron as thermometric species. Observed temperatures show significant differences with respect to each other. Argon emission lines exhibit a pronounced afterglow enhancement which is not observed for analytical lines. The relation-ship between excitation temperature and afterglow enhancement was studied. Excitation temperature was found to decrease suddenly at the falling edge of the microwave pulse.

Evaluation of Line and Continuum Sources for Atomic Fluorescence Spectrometry Using a Low-Powered Argon Microwave-Induced Plasma

An atomic fluorescence spectrometry system employing a low-powered, highly efficient MIP as the atom cell (MIP-AFS) has been developed and is evaluated with the use of direct aqueous nebulization. The MIP-AFS system employs hollow cathode lamp and Xe-arc lamp excitation sources. Detection limits of 14 elements were studied and compared to results for ICP-AFS. Linear working ranges of at least 5 orders of concentration magnitude were found. Interelement effects (i.e., vaporization, ionization, and scatter interferences) were also investigated.

Moderate-power argon microwave-induced plasma for the detection of metal ions in aqueous samples of complex matrix

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTModerate-power argon microwave-induced plasma for the detection of metal ions in aqueous samples of complex matrixPeter G. Brown, David L. Haas, John M. Workman, Joseph A. Caruso, and Fred L. FrickeCite this: Anal. Chem. 1987, 59, 10, 1433–1436Publication Date (Print):May 15, 1987Publication History Published online1 May 2002Published inissue 15 May 1987https://doi.org/10.1021/ac00137a013RIGHTS & PERMISSIONSArticle Views51Altmetric-Citations19LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (493 KB) Get e-Alerts Get e-Alerts