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In this study, we present a novel pulsed microwave-induced plasma (MIP) source coupled with a glow discharge for optical emission spectrometry (MIP-OES), operating at 1000 W power and a frequency of 2.45 GHz. The MIP cavity consists of a stainless steel cylindrical waveguide connected to a circular resonator made of the same material, joined through a dielectric quartz disc. The output of the MIP cavity is linked to a closed glow discharge quartz tube and a mechanical pump. Numerical simulations were employed to optimize the structure and dimensions of the MIP cavity. The nozzle position of the cylindrical resonator's output was precisely adjusted to align with the maximum magnetic field, achieving the TM011 mode, which results in a point plasma with high density. This configuration enables the cavity to produce a dense, warm plasma emission zone with a consistent emission rate around the circumference of the emitting source. The results demonstrate that the designed MIP source exhibits a significantly higher density and temperature compared to other sources with similar microwave parameters. [ABSTRACT FROM AUTHOR]

The utilization of hydrogen as an energy carrier faces a challenge due to its limited presence in its pure form in the Earth's atmosphere, necessitating its extraction from various sources. Among hydrogen production methods, microwave-induced plasma molecular cracking shows promise as an alternative. This review explores how different operational parameters of a microwave-induced plasma system with gas-phase discharge impact hydrogen production performance. Performance indicators include hydrogen production rate, energy yield, and final hydrogen concentration. Parameters influencing hydrogen production encompass microwave power, gas flow rate, initial hydrogen concentration, steam addition, gas injection method, and plasma-forming gas type. Other vital system parameters are also discussed. Higher absorbed power leads to increased hydrogen production, albeit less efficiently. Elevated carrier gas flow rate reduces residence time, consequently lowering performance, while higher fuel gas flow rates enhance hydrogen production. Introducing steam can enhance indicators and reduce soot, and injecting fuel gas directly into the plasma torch tip yields optimal hydrogen production. Avoiding excessive power, fuel gas flow, or water vapor is important, as hydrogen saturation can limit further performance enhancement. • Microwave-induced plasma appears as a promising alternative for H 2 production. • Operational parameters' impacts on the system performance were analyzed. • Steam addition and gas injection methods' impacts on H 2 production were discussed. • Optimal practices for enhanced H 2 production were determined. [ABSTRACT FROM AUTHOR]

To obtain reliable results in the quantitative determination of rare earth elements (REE) by atomic emission spectroscopy, it is particularly important to take into account the matrix effects of the macrocomponents contained in the analyzed solutions. Analytes obtained by liquid-phase and autoclave opening of geological samples of REE ores and minerals contain significant amounts of strong mineral acids used as reagents and such macrocomponents of the samples as aluminum (aluminosilicates) and phosphorus (phosphates in apatites). Here, we studied the effects of hydrochloric, nitric, sulfuric, and orthophosphoric acids and aluminum on the relative intensity of the ion analytical lines of La, Ce, Nd, Sm, Gd, Tb, Er, and Yb in atomic emission spectroscopy of the microwave-induced plasma (AES MIP). With an increase in the acid concentration from 0 to 1 mol/L, the relative intensity of the spectral lines of all investigated REE decreased monotonically by 10–20%. The depressing effect of aluminum, which is due to a decrease in the degree of ionization of REE atoms, was much stronger and reached 70%. It was shown that the AES MIP method is not inferior to atomic emission spectroscopy of inductively coupled argon plasma in terms of the detection limits of lanthanum, cerium, gadolinium, and erbium.

As a typical carbamate pesticide, methomyl was once widely used in agriculture for its excellent broad-spectrum insecticidal effect. However, due to its high toxicity, long half-life, and difficult degradation properties, it poses a serious challenge to water environment pollution. In this study, an electrode-free discharge microwave-induced plasma technology was used to rapidly and efficiently degrade methomyl in aqueous solution. In this experiment, the statistical design of experiments (DOE) was adopted to optimize the plasma degradation parameters. Under the optimized parameters (P = 140 W, D = 0 mm, R = 0.5 L/min), 78.4% removal of 50 mg/L of methomyl was achieved after 8 min. The optical emission spectrometry and free radical detection experiments showed that the active substances generated by the collision reaction between plasma and water molecules occurring at the gas–liquid interface were the key factors to exert the degradation effect. The degradation rate of methomyl decreased by 73.2% after the addition of tert-butanol (OH burster), while it decreased by only about 12.0% after the addition of peroxidase. These implied that ∙OH was largely responsible for methomyl degradation. In addition, based on the detected intermediates, possible degradation mechanisms and pathways were analyzed. [ABSTRACT FROM AUTHOR]

The objectives of this work are to develop nanocarrier systems for the Ru(II)-p-cymene naproxen antitumor metallodrug, [Ru(η6-p-cymene)(npx)Cl] or Rupcy, based on polymeric nanoparticles (NPs) composed by the biodegradable poly(lactic acid) (PLA) and the hydrophilic polymerised β-cyclodextrin (PolyCD); to validate an analytical method for determination of Ru incorporated into the metallodrug loaded-NPs. The PolyCD was prepared by single step condensation and polymerisation reaction and incorporated as a polymer blend during the fabrication of PLA/PolyCD blends NPs and also as a core/shell structure built by adsorption of the PolyCD onto the surface of PLA NPs to give PLA(core)/PolyCD(shell) NPs. Three different loaded-systems incorporating the metallodrug (Rupcy-PLA NPs (1), Rupcy-PLA/PolyCD blends (2), and Rupcy-PLA(core)/PolyCD(shell) NPs (3)) were prepared by nanoprecipitation. The characterisation was performed by Proton Nuclear Magnetic Resonance, Matrix Assisted Laser Desorption/Ionization Time-of-Flight, Fourier-Transform Infra-red and UV-VIS Electronic Absorption Spectroscopies, Thermogravimetric Analysis, Differential Scanning Calorimetry, Dynamic Light Scattering, and Electrophoretic Light Scattering. Ru was determined by Microwave Induced Plasma Optical Emission Spectrometry (MIP-OES) with validation of the method. The metallodrug entrapment efficiency was around 90% (w/w) and drug loading was at 3–4% (w/w). The characterised metallodrug-loaded systems exhibited monomodal size distributions and appropriate hydrodynamic diameters [218.3 ± 13.5 (1), 205.4 ± 14.4 (2), 231.5 ± 22.0 (3) nm] and zeta potential values [−31.5 ± 2.2 (1), −26.1 ± 4.5 (2), −28.8 ± 6.1 (3) mV]. The validation of the MIP-OES method by evaluating selectivity, linearity, precision, accuracy, and limits of detection and quantification succeeded. The NPs parameters are compatible with colloidally stable systems. The MIP-OES method showed to be simple, reliable, and feasible to quantify indirectly the amount of the metallodrug-loaded into the PLA NPs. [ABSTRACT FROM AUTHOR]

Transition metal nitrogen carbon based single‐atom catalysts (SACs) have exhibited superior activity and selectivity for CO2 electroreduction to CO. A favorable local nitrogen coordination environment is key to construct efficient metal‐N moieties. Here, a facile plasma‐assisted and nitrogen vacancy (NV) induced coordinative reconstruction strategy is reported for this purpose. Under continuous plasma striking, the preformed pentagon pyrrolic N‐defects around Ni sites can be transformed to a stable pyridinic N dominant Ni‐N2 coordination structure with promoted kinetics toward the CO2‐to‐CO conversion. Both the CO selectivity and productivity increase markedly after the reconstruction, reaching a high CO Faradaic efficiency of 96% at mild overpotential of 590 mV and a large CO current density of 33 mA cm‐2 at 890 mV. X‐ray adsorption spectroscopy and density functional theory (DFT) calculations reveal this defective local N environment decreases the restraint on central Ni atoms and provides enough space to facilitate the adsorption and activation of CO2 molecule, leading to a reduced energy barrier for CO2 reduction. [ABSTRACT FROM AUTHOR]

This article presents a new type of microwave-induced atmospheric-pressure low-temperature dielectric barrier discharge source, based on the principle of parallel plate transmission lines (PPTLs). This source is a simple structure with small size, large plasma discharge area, and low discharge temperature. Experiments show that linear plasma discharge with width of 15 mm can be obtained with input power of only 25 W at 2.45 GHz. The temperature of sample placed 1 mm vertically away from the nozzle and treated for 3 min is about 45 °C even with 60-W microwave input power, which proved its thermal safety even for the biomedical applications. Emission spectroscopy diagnosis indicates that the electron density of plasma can be controlled easily by adjusting the discharge gap and the dielectric thickness. It makes this source available for various applications. This work provides a new approach to obtain uniform linear plasma. [ABSTRACT FROM AUTHOR]

As a prospective ignition technique, microwave-assisted spark ignition (MAI) can accelerate flame and thus satisfy the demand for effective ignition. However, its acceleration mechanism on flame velocity is still unclear, which hinders its application and optimizations. Therefore, this research focuses on understanding the flame acceleration mechanism behind MAI. In this paper, MAI is achieved through radiating a microwave pulse after spark ignition. The flame velocity and the precise absorbed energy under different combustion conditions are investigated with flame kernel's Schlieren images and microwave energy diagnostics, respectively. The results show that MAI accelerates flame primarily by the interaction between microwave plasma and flame front, rather than the free electrons within the flame. Specifically, microwave accelerating flame takes two processes: energy absorption, and velocity match. Energy absorption refers to the microwave energy absorbed by residual electrons after ignition to generate and sustain microwave plasma, while velocity match involves the outward plasma with faster velocity propelling the slower flame front. Moreover, the plasma velocity shows a positive relationship with absorbed microwave energy. The velocity match between microwave plasma and flame is important to successful flame acceleration. Besides, the efficiency of energy absorption and flame acceleration varies with plasma type (glow or incandescent). Glow plasma is characterized by effective flame acceleration but relatively low absorption efficiency, and incandescent plasma is in reverse. The maximum absorption efficiency can be elevated to 70 % with incandescent plasma occurring. Ultimately, the plasma velocity declines with its traveled distance, which might impair the flame acceleration. [ABSTRACT FROM AUTHOR]

Microwave-induced plasma optical emission spectrometry (MIP OES) has increasingly become a major resource for multi-elemental analysis. One of the greatest breakthroughs in the field has been the development of a commercial instrument based on a Hammer cavity, which runs on N 2 gas obtained from an air compressor and a N 2 generator. Here, we describe the most recent advances in MIP OES instrumentation, as well as related developments in sample preparation and alternative sample introduction systems, strategies to reduce the effects of background emission and analytical signal fluctuations on accuracy, and new calibration and plasma diagnostics methods. Recently published studies have contributed to minimize matrix effects and improve robustness of MIP OES analysis, which allowed for applications involving a broad range of analytes and sample types. Together, the array of recent developments in MIP OES contributes to its acceptance and increasing adoption as a cost-effective alternative in trace element analysis. Image 1 • The most recent developments in MIP OES instrumentation are discussed. • MIP OES increasingly becomes a consolidated method in trace element analysis. • MIP OES-related sample preparation and sample introduction systems are reviewed. • Plasma diagnosis and signal correction methods for improving MIP OES are discussed. • Novel calibration methods used with MIP OES for accurate analysis are reviewed. [ABSTRACT FROM AUTHOR]

In this work, we evaluate the application of microwave-induced plasma optical emission spectrometry (MIP OES) to determine of Al, Cr, Co, Cu, Fe, Mn, Ni and Zn in children’s cough syrup, eye drops, and oral antiseptic using standard dilution analysis (SDA). The SDA method is simple, with only two calibration solutions prepared per sample. The first solution (S1), composed of 50% sample +50% of a standard solution, is introduced into the plasma and the analytical signals are monitored in a time-resolved fashion. Then, the second solution (S2), composed of 50% sample +50% blank, is poured into the vial containing S1. As the solutions mix, the analytical signals gradually drop to a stable baseline. The calibration curve is computed by plotting the ratio of the analyte signal (SA) over the internal standard signal (which is also part of S1) (SIS) on the y-axis, versus the inverse of the IS concentration on the x-axis (i.e., SA/SIS versus 1/CIS). In this study, SDA results were compared with values obtained with the traditional methods of external calibration (EC), internal standardization (IS), and standard additions (SA) in MIP OES determinations. The precision (represented as percent RSD) for SDA showed values in the range of 2.50–8.00% for all samples, while conventional calibration methods showed RSDs in the range of 6.40–32.50% for EC, 8.30–21.80% for IS, and 5.20–17.40% for SA. The LODs calculated for SDA are below the maximum limits allowed by the major pharmaceutical regulatory agencies, and presents superior precision and accuracy compared to the traditional calibration methods. Considering its simplicity and efficiency, SDA is an important new tool for accurate analyses of pharmaceuticals. [ABSTRACT FROM AUTHOR]

As a prospective ignition technique, microwave-assisted spark ignition (MAI) efficiently enhances ignition with plasma absorbing microwave energy. This paper achieves MAI through radiating a single 0.2 ms microwave pulse after the initial spark ignition, and investigates the ignition performance and the precise absorbed energy of MAI in different absorption patterns. The absorption pattern is tailored by the microwave pulse power. The results show that the enhancement of MAI can be divided into two categories based on ignition performance and absorbed energy: the glow enhancement and the incandescence enhancement. Compared to the glow enhancement, the incandescence enhancement has a greater energy absorption efficiency and thus induces more significant ignition enhancement. Additionally, the effect of gas parameters, including gas pressure and components, on these two enhancement categories is studied. Increasing pressure or decreasing methane concentration facilitates the generation of incandescence enhancement. Ultimately, the causes of both enhancements are discussed. The incandescence enhancement may be originated from the ionization of metal particles in the microwave field, whereas the glow enhancement is attributed to gas ionization. This work highlights the potential application of metal-microwave discharge on MAI, which can play a crucial role in suiting different conditions and further understanding the mechanisms of MAI. [ABSTRACT FROM AUTHOR]

A novel centralized microwave jet burner system is proposed here that can be used as a test platform to enable studies of plasma-assisted combustion (PAC) under various operation conditions and combustible mixtures. Spectroscopic characterizations of this burner are conducted using optical emission spectrum with methane/O2/N2and methane/O2/Ar mixtures for comparison to distinguish the effects of the bath gas on flame enhancement and to delineate the flame enhancement mechanism of microwave induced plasma. The results show that the flame enhancement, by applying a nonequilibrium plasma, is more efficient when the dilution inert N2in the air is replaced by Ar. The bath gas in the oxidizer stream plays an important role in the flame enhancement mechanism for the PAC system through more efficient direct impact of excited electrons on oxygen in the plasma and resulting in earlier initiation of the chain reactions through branched OH formation reactions in the flame. [ABSTRACT FROM AUTHOR]

In this work, standard dilution analysis (SDA) is combined with microwave-induced plasma optical emission spectrometry (MIP OES) to determine seven elements in coffee, green tea, energy drink, beer, whiskey and cachaça (Brazilian hard liquor). No sample preparation other than simple dilution in HNO 3 1% v v −1 is required. Due to relatively low plasma temperatures, matrix effects may compromise accuracies in MIP OES analyzes of complex samples. The method of standard additions (SA) offers enhanced accuracies, but is time-consuming and labor intensive. SDA offers a simpler, faster approach, with improved accuracies for complex matrices. In this work, SDA's efficiency is evaluated by spike experiments, and the results are compared to the traditional methods of external calibration (EC), internal standard (IS), and standard additions (SA). SDA is comparable to the traditional calibration methods, and it provides superior accuracies for applications involving ethanol-containing beverage samples. The SDA-MIP OES procedure is effective. Using only two calibration solutions, it may be easily automated for accurate and high sample throughput routine applications. [ABSTRACT FROM AUTHOR]

A novel analysis online system based on direct coupling of micro-fluidic μchip-based photo-micro-reactor/ultrasonic nebulization (μchip-UV/MR/USN) to microwave induced plasma-optical emission spectrometry (MIP OES) for simultaneous determination of inorganic trace elements in human body fluids and water samples was developed. A univariate approach and the simplex optimization procedure were used to achieve optimized conditions and derive analytical figures of merit. Minimum dead volume, high photo-decomposition and nebulization efficiency and high sample transport efficiency were obtained by using this interface. The experimental concentration detection limits for simultaneous determination, calculated as the concentration giving a signal equal to three times the standard deviation of the blank (LOD, 3σ blank criterion, peak height) were 30, 6, 1, 2, 10, 2, 7, 5, 8, 10, 9 and 30 μg L − 1 for Ba, Ca, Cd, Cu, Fe, Li, Mg, Mn, Pb, Sr, Zn and C, respectively. Repeatability expressed as the relative standard deviations (RSD, n = 6) for the target elements ranged from 4% to 8%. Quantitative data obtained for Seronorm urine and water reference materials were in good agreement with the corresponding reference values, proving the potential of this analysis system for multi-element trace analysis via MIP OES. The proposed method had been successfully applied for the determination of inorganic trace elements in urine, mineral water and implant fluid samples. The developed method is quite suitable for routine analysis of inorganic trace elements in biological and environmental fields and precious biological samples such as implant fluids. [ABSTRACT FROM AUTHOR]

An innovative method of volatile organic compounds analysis by using microwave-induced plasma ionization (MIPI) source in combination with an ambient ion trap mass spectrometer is presented here. Using MIPI for direct sample vapor, analysis was achieved without any sample preparation or subsequent heating. The relative abundance of the target compounds can be obtained almost instantly within a few seconds. The ionization processes of different volatile compounds was optimized, and the limits of detection were identified in the range of 0.15-4.5 pptv or 0.73-8.80 pg ml−1. The relative standard deviation (RSD) is in the range of 4-14%, while correlation coefficients of the working curves ( R2) are better than 0.98. The new method possesses advantages of ease operation, time-saving, high sensitivity and inexpensive setup. In addition, the ionization processes of short n-alkane chains were investigated with the MIPI technique, and a unique [M + 13]+ was detected, which has not been reported in detail by any other related ionization techniques. An ionization mechanism was proposed on the basis of the experimental results obtained in this work and available information in literatures, in which the n-alkanes in the plasma environment possibly generate protonated cyclopentadiene [M - 5]+ or alkyl-substituted analogues as well as hydrous ions [M + 13]+ and [M + 13 + 18]+, as shown in Scheme 1 in the main text. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Microwave-induced plasma optical emission spectrometry (MIP-OES) using Okamoto-cavity was investigated in the determination of manganese, in comparison with argon radio-frequency inductively-coupled plasma (ICP)-OES. An important point of this study is that, in the Okamoto-cavity MIP, the emission intensity of particular atomic emission lines is much elevated by adding oxygen of ca. 10% to the nitrogen matrix plasma gas. Intensity variations in emission lines of manganese atom as well as the ion and in a band head of nitrogen molecule were observed, when oxygen was added to the nitrogen plasma, indicating that the emission intensity of the atomic lines was drastically elevated while the intensities of the ionic lines and the nitrogen band head decreased in a similar manner. This observation can be explained by the fact that the nitrogen excited species, contributing to the transition of the band head, are consumed through collisions with oxygen molecules to cause their dissociation, and eventually manganese atoms in the nitrogen–oxygen plasma would be less ionized than in the pure nitrogen plasma, because the ionization of manganese is also caused by collisions with the nitrogen excited species. Optimization of the measuring parameters in the Okamoto-cavity MIP-OES was conducted for the determination of manganese; as a result, the Mn I 403.076-nm line was recommended as the analytical line in the nitrogen-oxygen mixed gas MIP, while the most intense ionic line, Mn II 257.065nm, should be employed in the argon ICP. Their detection limits were of the same order, implying that the Okamoto-cavity MIP had as good analytical performance as the conventional ICP. [Copyright &y& Elsevier]

Organic germanium compounds, especially Ge-132, more corrctly denoted as bis-beta-carboxyethyl germanium sesquioxide ([Ge(=O)CHCHCOH]O), are of continued interest as they are said to promote health and display anticancer activity. Although these beneficial effects have never been substantiated by comprehensive clinical studies, this drug can still be obtained through various sources and is usually marketed as a nutritional supplementation rather than an anticancer medication. As the quality standards under which this drug is produced are unknown, the need for an effective quality control of these products arises. To date, Ge-132 is considered generally as a safe compound for application in contrast to inorganic germanium which demonstrates severe renal toxicity. In this paper, a new approach to the determination of Ge-132, based on derivatization by ethyl chloroformate reagent (ECF), in the presence of ethanol and pyridine in the mixture, and subsequent analysis by gas chromatography coupled with microwave-induced plasma-atomic emission detection (GC-MIP-AED), is reported. Reaction conditions of the derivatization procedure were optimized with particular respect to the reagent (ECF) and catalyst (pyridine) concentrations. The proposed method is capable of distinguishing Ge-132 from inorganic germanium. The derivatization procedure was also tested with the use of methyl chloroformate (MCF) as alternative reagent, providing interesting additional information about the nature of the final product and the proposed reaction scheme. Among the two types of chloroformates, i.e., MCF and ECF, the latter proved to be more suitable for the proposed method, providing a calibration curve of superior sensitivity and linearity compared with the one obtained with MCF. The method was applied successfully in three real samples, two food supplements, and one commercially available fertilizer. The analysis of the Ge-132 derivative showed good linearity in the concentration of 1-250 mg L ( r = 0.9986) and a satisfactory precision (RSD = 6.8 %), which qualifies the proposed method for the speciation analysis of Ge in various matrices. [ABSTRACT FROM AUTHOR]

This work describes the development of a fast method for speciation analysis of triethyl-lead and tributyl-tin species in urine samples after in situ derivatization by tetraethyl- or tetrapropyl-borate reagents. The alkylation reaction is done in the aqueous and urine medium and the less-polar derivatives are extracted in hexane by liquid-liquid extraction. The species were extracted and the extract was efficiently collected from the aqueous phase after centrifugation. Finally, the organometallic species are separated by gas chromatography and determined from the emission signals of elemental lead and tin. Atomic lead and tin are formed from the organolead and organotin compounds during atomization of the column eluate in a microwave-induced helium plasma source. The simultaneous measurement of lead (Pb) at 405.780 nm and tin ( Sn) at 303.419 nm was achieved by an atomic emission detector. Finally, the analytes were determined with satisfactory precision (<5%) and detection limits of 0.05 μg Pb/ L and 0.48 μg Sn/ L, respectively, when 10 m L of urine is extracted with 1 m L of hexane and 1 μ L of extract is injected. [ABSTRACT FROM AUTHOR]

Abstract: Cavity Ring-Down Spectroscopy with a tunable diode laser has been used for the detection of fluorine at trace levels. A homemade experimental setup was constructed to accommodate the microwave-induced plasma glow discharge inside the optical cavity. The energy delivered by helium plasma discharge was successfully used not only for the dissociation of fluorine molecules but, more importantly, also for the excitation of fluorine atoms into their metastable level 3s4P5/2. The absorption observed at the 3s4P5/2–3p4Do 7/2 transition (corresponding to a 685.603-nm atomic line) was used for fluorine atom detection. Good agreement between theoretical and measured absorption line shapes confirmed the selectivity of fluorine atomic absorption. We observed an absorption coefficient of 4∙10− 6 cm− 1, corresponding to a detection of F(3s4P5/2) atoms at about 1.5∙106 atomscm− 3. These data demonstrate that we achieved a detection limit of 100ng g− 1 under the conditions of our initial homemade experimental setup. However, the optimization of the system may lead to the improvement of the detection limit by approximately two orders of magnitude. [Copyright &y& Elsevier]

A spectrometric determination of aqueous fluoride has been improved by coupling of continuous powder introduction microwave-induced plasma optical emission spectrometry with separation of the analyte onto powdered sorbents. A selective solid phase extraction method for preconcentrating trace fluoride from aqueous environmental samples on calcium hydrogenphosphate dihydrate in batch operation was employed while, for flow operation, the zirconium modified activated carbon method was adopted. The fluoride could be readily excited in helium plasma at 685.6 nm. Using a 1-L sample volume and a preconcentration factor of 1000, practical detection limit with respect to water sample is in the range 4.0-4.7 ng mL-1, depending on the sorbent used. External calibration was done using standards obtained by the dropping of standard fluoride solution on the powdered sorbent covering fluoride content from 50 to 5000 µg g-1. The procedure was applied to the determination of fluoride in mineral waters and certified reference material (CRM) drinking water. [ABSTRACT FROM AUTHOR]

In the past few years, microwave induced plasma optical emission spectrometry (MIP-OES) has generated great interest as an alternative technique to inductively coupled plasma-based techniques due to its lower operational cost. Since MIP-OES suffers from severe matrix effects due to easily ionizable elements (EIEs) (Na, Ca, etc.), it is unclear whether this technique could be employed for elemental bioavailability studies in soils and sediments since the main extractant solutions employed in such works may contain high levels of these elements. Thus, the aim of this work was to evaluate the feasibility of MIP-OES as a detector for such applications. To this end, the influence of different extractant solutions (0.25 mol L−1 MgCl 2 , 0.25 mol L−1 CaCl 2 , 0.10 mol L−1 acetic acid, 0.05 mol L−1 Na 2 EDTA, 0.25 mol L−1 NaNO 3 , 0.25 mol L−1 NaOAc/HOAc and 0.10 mol L−1 NH 2 OH·HCl) on the analyte emission of several elements (As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Rh, Se, Sr and Zn) was investigated. Results were compared to those obtained using a reference solution made of 5% w w−1 HNO 3 solution. For saline extractant solutions, both the optimum nebulizer gas flow rate (Q g) and analyte emission were modified with regard to the reference solution. In general, the optimum Q g was reduced by between 0.1 and 0.2 L min−1 for both ionic and atomic lines. Under optimum Q g conditions, analyte emission was supressed by saline solutions except for atomic lines with an upper electronic state below 4 eV, which were enhanced. The magnitude of matrix effects was strongly dependent on EIE ionization energy. The lower the ionization energy, the greater the matrix effects were registered. No measurable matrix effects were registered on both Q g and analyte emission within experimental uncertainties for NH 2 OH·HCl and acetic acid extractant solutions. Experimental data suggest that matrix effects were related to changes in plasma characteristics and the analyte excitation/ionization mechanism. To mitigate matrix effects and improve long-term MIP-OES performance, internal standardization using either Rh (343.489 nm and 369.236 nm) or OH molecular emission band (308.958 nm) was required. This calibration methodology was successfully applied to the study of the elemental bioavailability in soil samples from a vineyard affected by copper-based fungicides and sediment samples from an area affected by mining waste. [Display omitted] • MIP-OES is suitable as a detector for elemental bioavailability studies. • Saline extraction solutions affect to Q g and the analyte emission signal. • Matrix effects depend on wavelength characteristics and the extractant solution. • Internal standard mitigates matrix effects and improve long-term MIP-OES performance. [ABSTRACT FROM AUTHOR]

Abstract: A novel magnetically excited microwave plasma emission source was developed and tested. Unlike previous microwave plasma sources which couple energy from the microwave electric field, this source couples energy from the magnetic field. The resultant plasma shape allows easy entrainment of wet sample aerosol, such as is produced by a conventional inductively coupled plasma (ICP) nebulizer and spray chamber, into the core of the plasma. Plasma support gas can be either nitrogen or air although better sensitivity is achieved using nitrogen. Good stability of operation was observed for both aqueous and organic solvents over a wide range of sample flows. The measured performance when used as a spectroscopic source in conjunction with an echelle polychromator showed detection limits approaching those of commercial ICP sources. [Copyright &y& Elsevier]

Abstract: Hollow alumina microspheres have been prepared by microwave-induced (MI) plasma pyrolysis of atomized aerosols of precursor solutions and subsequent calcination at 1300°C for 2h. When an aqueous solution of 0.5moldm−3 Al(NO3)3 without any additives was used as a precursor, hollow α-Al2O3 microspheres with a thick shell wall were prepared after post-calcination at 1300°C. The addition of a polypropylene (PO)–polyethylene(EO) blockcopolymer (molecular weight: 2900–6500) to the precursor solution was effective for increasing the yield of hollow microspheres, but resulted in the formation of many cracks and holes in the thinned shell wall. Hollow alumina microspheres with a thin, but strong, shell layer could be prepared by the simultaneous addition of tetraethylorthosilicate. [Copyright &y& Elsevier]

Abstract: Nickel titanium (NiTi) plate of 1.2mm thickness was successfully clad on AISI 316L stainless steel substrate by a microwave-assisted brazing process. Brazing was conducted in a multimode microwave oven in air using a copper-based brazing material in tape form. The brazing material was melted in a few minutes by microwave-induced plasma initiated by conducting wires surrounding the brazing assembly. Metallographic study by scanning-electron microscopy (SEM) and compositional analysis by energy-dispersive spectroscopy (EDS) of the brazed joint revealed metallurgical bonding formed via inter-diffusion between the brazing filler and the adjacent materials. A shear bonding strength in the range of 100–150MPa was recorded in shear tests of the brazed joint. SEM and X-ray diffractometry (XRD) analysis for the surface of as-received NiTi plate and NiTi cladding showed similar microstructure and phase composition. Nanoindentation tests also indicated that the superelastic properties of NiTi were essentially retained. The cavitation erosion resistance of the NiTi cladding was essentially the same as that of as-received NiTi plate, and higher than that obtained in laser or TIG (tungsten-inert gas) surfacing. The high resistance could be attributed to avoidance of dilution and defect formation in the NiTi clad since the cladding did not undergo melting and solidification in the brazing process. Electrochemical tests also recorded similar corrosion resistance in both as-received NiTi and NiTi cladding. Thus, the present study indicates that microwave-assisted brazing is a simple, economical, and feasible process for cladding NiTi on 316L stainless steel for enhancing cavitation erosion resistance. [Copyright &y& Elsevier]

A nitrogen-oxygen mixed gas microwave-induced plasma with an Okamoto cavity was employed as an atomization and excitation source for emission spectrometric analysis of organic solvent samples. Nitrogen–oxygen mixed gas produces very a stable microwave-induced plasma that is highly robust to the loading of 4-methyl-2-pentanone (MIBK), possibly because the organic solvent is completely combusted in the oxygen-containing plasma. After extracting test solutions containing Al, Co, Cr(III), Cu, Fe(III), Mo(VI), Ni, Pb with MIBK, both the aqueous phase and the organic phase were aspirated into the microwave-induced plasma, yielding linear calibration curves for both the species in the aqueous phase (Al, Co, Cr, Ni, and Pb) and those in the organic phase (Fe and Mo). These results indicate that Fe and Mo can be extracted with MIBK, which is explained by the partition coefficients of these elements in MIBK. [ABSTRACT FROM AUTHOR]

Abstract: A novel continuous powder introduction microwave-induced plasma atomic emission spectrometry method (CPI-MIP-AES) has been developed for trace determination of metals in ground and tap water samples after preconcentration on activated carbon. The experimental setup consisted of integrated rectangular cavity TE101 and vertically positioned plasma torch. The technical arrangement of the sample introduction system has been designed based on the fluidized bed concept. The satisfactory signal stability required for sequential analysis was attained owing to the vertical plasma configuration, as well as the plasma gas flow rate compatibility with sample introduction flow rate. The elements of interest (Cd, Cu, Cr, Fe, Mn, Pb, Zn) were preconcentrated in a batch procedure at pH 8–8.5 after addition of activated carbon and then, after filtering and drying of the activated carbon suspension, introduced to the MIP by the CPI system. An enrichment factor of about 1000-fold for a sample volume of 1 l was obtained. The detection limit values for the proposed method were 17–250 ng l−1. The proposed method was validated by analyzing the certified reference materials: SRW “Warta” Synthetic River Water and BCR CRM 399 major elements in freshwater. The method was successfully applied to the determination of the heavy metals in tap water samples. [Copyright &y& Elsevier]

Abstract: A nitrogen–oxygen mixed gas microwave-induced plasma (MIP) with an Okamoto cavity was utilized as an atomization and excitation source for emission analysis when organic solvent samples are directly aspirated. Compared with the pure nitrogen plasma (excitation temperature of 5650 K), the excitation temperature in the nitrogen–oxygen mixed gas plasma (5100 K) was reduced, and thus, the detection sensitivity of ionic emission lines requiring higher excitation energy was degraded. However, nitrogen–oxygen mixed gases could produce the very stable microwave-induced plasma with a high robustness against the loading of ethanol solution. This effect might be because the organic solvent was completely burned in the oxygen-containing plasma. The excitation temperature was almost independent of the ethanol content in sample solutions, implying that the analytical performance was less effected by introducing organic solvent samples. [Copyright &y& Elsevier]

The use of solid-phase microextraction (SPME) with gas chromatography coupled to microwave-induced plasma atomic-emission detection (GC-MIP-AED) is described for selenite [Se(IV)] speciation. Aqueous standards were derivatised with sodium tetraethyl- or tetrapropylborate and extracted by SPME. Headspace extraction of the ethyl and propyl derivatives was studied. Relevant experimental conditions were optimised, including conditions for derivatisation and extraction and those of gas chromatographic analysis. The limits of detection achieved for headspace sampling of derivatised Se(IV) were in the low ng mL-1 range for both ethylation and propylation. When the method was applied to analysis of selenite in selenised yeast reference material results were in good agreement with the indicated values. [ABSTRACT FROM AUTHOR]

This article presents recent advances in the hydride-generation (HG) technique hyphenated with different discharges of the atomic emission spectrometry (AES) [i.e. inductively-coupled plasma (ICP), microwave-induced plasma (MIP), direct-current plasma (DCP) and glow discharge (GD)], serving as excitation sources of hydride-forming elements. It surveys and discusses various aspects of vapour-phase introduction, comprising the instrumentation for performing the reaction, the influence of the chemical reaction conditions, the existence of chemical and non-chemical interference effects and the approaches to eliminating or lessening the interferences, as well as the analytical applications to real samples. In addition, it presents the latest trends in the technique, such as expansion of the scope to some transition and noble metals and the usage of organised surfactant-based media for the enhancement of the reaction properties. [Copyright &y& Elsevier]

Low power microwave-induced argon plasma generated by resonant TE101 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 (Trot) determination, while the atomic emission lines of Ar, H and Sb were applied for excitation temperature (Texc) measurement. Assuming a Boltzmann distribution, the temperatures were calculated with the aid of the least squares method. Electron number density (ne) derived from Stark broadening of the Hβ line was found to be between 2.5×1015 and 0.57×1015 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 Trot(OH) increased from 2970 to 3820 K while Trot(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. [Copyright &y& Elsevier]

Tungsten devices have been employed in analytical atomic spectrometry for approximately 30 years. Most of these atomizers can be electrically heated up to 3000 °C at very high heating rates, with a simple power supply. Usually, a tungsten device is employed in one of two modes: as an electrothermal atomizer with which the sample vapor is probed directly, or as an electrothermal vaporizer, which produces a sample aerosol that is then carried to a separate atomizer for analysis. Tungsten devices may take various physical shapes: tubes, cups, boats, ribbons, wires, filaments, coils and loops. Most of these orientations have been applied to many analytical techniques, such as atomic absorption spectrometry, atomic emission spectrometry, atomic fluorescence spectrometry, laser excited atomic fluorescence spectrometry, metastable transfer emission spectroscopy, inductively coupled plasma optical emission spectrometry, inductively coupled plasma mass spectrometry and microwave plasma atomic spectrometry. The analytical figures of merit and the practical applications reported for these techniques are reviewed. Atomization mechanisms reported for tungsten atomizers are also briefly summarized. In addition, less common applications of tungsten devices are discussed, including analyte preconcentration by adsorption or electrodeposition and electrothermal separation of analytes prior to analysis. Tungsten atomization devices continue to provide simple, versatile alternatives for analytical atomic spectrometry. [Copyright &y& Elsevier]

Injectable fiducial markers are crucial in image-guided radiation therapy (IGRT) due to their minimally invasive operations and improved patient compliance. This study presents the development of a ready-to-use injectable fiducial marker utilizing alginate stabilized-gold nanoparticles (alg-Au NPs) and a body temperature-activated in situ gel-forming system. Gram-scale alg-Au NPs were prepared in an hour by a green microwave-induced plasma-in-liquid process (MWPLP). Sodium alginate was introduced in this process to avoid aggregation between Au NPs, which ensured their stability and injectability. The gelation behavior of alginate with divalent cations and a temperature-dependent release of calcium source (glucono-delta-lactone (GDL) and CaCO 3 ) served as the foundation of the body temperature-activated in situ gel-forming system. The injectable fiducial marker GDL/CaCO 3 /alg-Au NPs could maintain a liquid state at a low temperature for a higher injectability. After injection, on the other hand, Ca 2+ would be released due to the body temperature-activated hydrolysis of GDL and the subsequent reaction with CaCO 3 , which would initiate the gelation of alginate. The injectable fiducial marker can be therefore delivered via injection and form gel at target site to avoid marker movement or Au NPs leakage after injection. Rheological measurements demonstrate the stability and gelation behavior of GDL/CaCO 3 /alg-Au NPs at different temperatures. Furthermore, the injectability and imaging ability of GDL/CaCO 3 /alg-Au NPs were also examined. In summary, ready-to-use injectable fiducial marker GDL/CaCO 3 /alg-Au NPs were developed via a green and facile method for IGRT.

The investigation of surface-wave plasmas has led to a considerable improvement in the current understanding of the general HF discharges. The power loss per electron, π, is a parameter of equilibrium which plays the leading role in the modelling of the surface-wave plasma and in the elaboration of a unified model for HF discharges in general. In this paper, we use the total losses by ambipolar diffusion and recombination to obtain an empirical description of the dependence of π on the neutral gas temperature. [ABSTRACT FROM AUTHOR]

Being an element-selective detector, the plasma emission detector was used to determine carbon in organic compounds. Experiments were carried out with the aid of osculating interference filters and lock-in amplifiers. The obtained signals were processed by a fast-Fourier-transform analyzer to study their frequency spectra. Results are given for the detection of carbon. Furthermore studies on the influence of angle-adjustment, microwave power, photomultiplier voltage and oscillation frequency on the determination of fluorine in organic compounds were carried out and results for detection limits and dynamic range of this method are presented. [ABSTRACT FROM AUTHOR]

Microwave-induced plasma under atmospheric pressure is an effective technique for catalyst preparation. A Pd/Al2O3 catalyst was prepared using a fixed bed with microwave plasma irradiation. The activity of the catalyst was compared with that of catalysts made using the plasma spouted bed and the conventional furnace. From the results of X-ray powder diffraction (XRD) spectra and transmission electron microscopy (TEM) images, plasma treatment induced a rapid reduction process (PdO→Pd). Moreover, the plasma treatment derived the growth of a different facet from Pd (111) to Pd (100). A different kind of phase transition behavior was observed with plasma-treated alumina. H2 chemisorption analysis confirmed that the plasma treatment had a positive effect on the dispersion of Pd metal on the support. These improvements to the properties of the catalyst resulted in excellent performance in hydrogenation of acetylene. [ABSTRACT FROM AUTHOR]

The emission spectra of C2(d3Πg–a3Πu), CH(A2Δ–X2Π), and CH(B2Σ–X2Π) bands are analysed to measure rotational Trot, vibrational Tvib, and gas temperature Tg from Ar/C2H2 (5–20% C2H2) microwave‐induced plasma (MIP). In case when helium and hydrogen are used in the gas mixture instead of argon, no significant change in Trot is noticed. Both studied temperatures are insensitive in terms of the C2H2 percentage. From CH(0–0, A2Δ–X2Π) band R2 branch lines, two Trot (Trot ∼ 520–580 K for J′ = 3–9 and Trot ∼ 1,700–1,800 K for J′ = 10–17) are determined. The lower Trot equals the Tg (500–700 K) measured from C2 bands in this study. The H2 Fulcher‐α diagonal bands are recorded as well in the H2/C2H2 mixtures and Trot∼750–900 K of the H2 ground state measured. Tvib ∼ 6,000 K in Ar/C2H2 MIP is calculated from the integral intensity ratio of C2(2,1) and C2(3,2) bands. [ABSTRACT FROM AUTHOR]

A microwave-induced plasma optical emission spectrometer with N 2 -based plasma was combined with a multimode sample introduction system (MSIS) for hydride generation (HG) and multielemental determination of As, Bi, Ge, Sb, and Sn in samples of forage, bovine liver, powdered milk, agricultural gypsum, rice, and mineral fertilizer, using a single condition of prereduction and reduction. The accuracy of the developed analytical method was evaluated using certified reference materials of water and mineral fertilizer, and recoveries ranged from 95 to 106%. Addition and recovery experiments were carried out, and the recoveries varied from 85 to 117% for all samples evaluated. The limits of detection for As, Bi, Ge, Sb, and Sn were 0.46, 0.09, 0.19, 0.46, and 5.2 μg/L, respectively, for liquid samples, and 0.18, 0.04, 0.08, 0.19, and 2.1 mg/kg, respectively, for solid samples. The method proposed offers a simple, fast, multielemental, and robust alternative for successful determination of all five analytes in agricultural samples with low operational cost without compromising analytical performance.