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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]

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]

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]

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]

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]