Advantages and effects of nitrogen doping into the central channel of plasma in axially viewed-inductively coupled plasma optical emission spectrometry (original) (raw)
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Effect of N 2 on the emission profile and excitation temperature in axially viewed plasma-ICP OES
J. Anal. At. Spectrom., 2015
Fundamental studies were conducted in order to gain useful insights about energy transfer that takes place when a low flow (20 mL min À1 ) of N 2 is introduced into the central channel of the Ar-ICP in inductively coupled plasma optical emission spectrometry (ICP OES). Axial and radial emission profiles of Mg(I), Mg (II) and Ar(I) were collected along and across the central channels of both Ar-ICP and Ar-N 2 -ICP. Axial profiles indicated a more energetic plasma close and above the load coil when N 2 was added. On the other hand, radial profiles suggested a wider and more uniform central channel with the N 2 flow addition.
Journal of Analytical Atomic Spectrometry, 2018
Five different glass sheathing devices were used to introduce 20 mL min À1 N 2 sheathing gas around the effluent from the spray chamber to see the effect of their dimensions on plasma robustness as measured using the Mg II 280.270 nm/Mg I 285.213 nm emission signal ratio in inductively coupled plasma (ICP) optical emission spectrometry (OES). A clear relationship between device dimensions and the plasma robustness profile along the ICP central channel was observed. With an aerosol inlet having an inner diameter of 1.0 cm in the sheathing device, mixing of N 2 with the aerosol was minimised and the resulting sheath increased robustness, the higher thermal conductivity of N 2 versus Ar likely improving energy transfer between the bulk plasma and the central channel. The configuration of the outlet is also important, as any bottleneck favours mixing of N 2 with the aerosol, which in turn cools the plasma, thereby shifting the region of maximum robustness to higher above the load coil. Regardless of device dimensions, plasma robustness was always better with N 2 sheathing gas. An increased ion-toatom emission signal ratio also resulted for other elements than Mg. The presence of N 2 also seems to affect excitation mechanisms, such as charge transfer between NO + and Cd or Ni, which appears to take place at higher observation height, after N 2 has had enough time to diffuse into the central channel.
J. Anal. At. Spectrom., 2015
A simple enhanced sample introduction system, using pneumatic nebulization (PN), was developed for inductively coupled plasma optical emission spectrometry (ICP OES). The aerosol generated by a Burgener parallel-flow nebulizer, coupled to a single-pass flip chamber (FC), was heated to 230 C using a ceramic infrared (IR) heater. Multivariate optimizations were conducted to find operating conditions that maximized analyte sensitivity while maintaining plasma robustness, as measured by the Mg II/Mg I intensity ratio. Other spray chamber designs, such as a single-pass (SP) and a custom Scott-type doublepass (DPE), were also tested in order to find the ideal combination with the Burgener nebulizer. Under optimum conditions and compared to conventional pneumatic nebulization at room temperature, a 6 fold improvement in sensitivity and a 4-7 fold improvement in detection limit was obtained for 38 elements using FC(IR), SP(IR) and DPE(IR). The improvement was more significant for ionic rather than atomic emission lines. Plasma robustness also increased significantly over room temperature PN.
Analytical Methods, 2014
This review deals with mixed gas Ar-N 2 plasmas, highlighting advantages, limitations and applications of them in inductively coupled plasma optical emission spectrometry (ICP OES), inductively coupled plasma mass spectrometry (ICP-MS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) techniques, covering publications in the last three decades. Fundamental plasma parameters (such as electron number density, excitation or ionization temperatures, oxides and spatial profiles of ion distribution), performance of the mixed gas Ar-N 2 plasmas, and figures of merit are presented and discussed in order to demonstrate the effects of adding N 2 to the Ar-ICP.
Spectrochimica Acta Part B: Atomic Spectroscopy, 1990
The high-resolution Fourier transform spectrometer (FIX) of the Los Alamos National Laboratory was used for diagnostic studies of Ar-N, ICP discharges, High-resolution FIS data were obtained to: (a) conduct analysis of line widths and line shapes for Fe lines to ascertain contributions from the Gaussian and Lore&an components; (b) to calculate the Doppler or translational temperatures of emitting species by using the half width of the Gaussian component; and (c) to determine excitation temperatures based on the relative intensities of many spectral lines. The effect of gas composition and plasma operating ~nditions on line widths, Doppler and excitation temperatures were examined.
Spectrochimica Acta Part B: …, 1993
Ah&act-A supplementary electrical discharge is generated by extracting the axial channel of an Ar inductively coupled plasma (ICP) through a circular (0.5 mm diameter) sampling orifice into a small vacuum chamber. Emission is observed from just outside the sampling orifice and from the adjacent region of the plasma upstream of the sampler. The discharge enhances the intensities of several Ca II and SC II lines but does not broaden the lines or otherwise perturb the line shapes. The sampling orifice does not introduce any additional memory or extend the rinse-out time required to change samples. Sodium concomitant at concentrations up to 1000 mg 1-l suppresses the intensities of analyte lines by 5-30%, depending upon the particular line involved. Sodium at 5000 mg 1-l suppresses either ion lines or neutral atom lines by 40-60%. This suppression effect is more severe than that generally observed under normal operating conditions when observing emission from the ICP alone. The additional suppression is attributed to a change in the spatial distribution of emission induced by the discharge and the gas flow into the sampler.
Spectrochimica Acta Part B: Atomic Spectroscopy, 2002
The analytical performance of two inductively coupled plasma optical emission spectrometers with axially and radially viewed configurations, equipped with charge coupled device solid-state detectors was evaluated using Ar, Ba, Mg, and Ni as test elements. Both instruments have similar Echelle optical arrangements and radio-frequency generators, differing only in the viewing mode and in the diameter of the central injector tube, i.e. 2.3 for the axially and 1.4 mm for the radially viewed ICP. The figures of merit evaluated were: warm-up time, short-and long-term stabilities, UV and VIS spectral resolution and limit of detection (LOD) for Ni in 0.14 mol l HNO and 1000 y1 3 mg l Cr media, respectively. The influence of residual carbon content on background equivalent concentration y1 (BEC) and sensitivity attained for Al, As, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Se and Zn was also investigated in both viewing modes. The robustness, short-and long-term stabilities, and UV and VIS spectral resolutions were similar for both configurations. For the radially viewed equipment, the warm-up time was at least a factor of 2 shorter than that for the axially viewed configuration. On the other hand, the sensitivity attained for Ni with the axially viewed arrangement was approximately 20 times better than that with the radially viewed. In both viewing modes, and for most of the evaluated elements, the values of BEC and LOD were similar for all studied carbon concentrations (from 10 to 10 000 mg l C) when working with robust plasma conditions. The Mg IIyMg I ratio at an applied power of y1 1.3 kW and a nebulizer gas flow-rate of 0.90 and 0.70 l min for axially and radially viewed configurations were y1 10.6 and 13.7, respectively. Quantitative determinations were successfully performed using both systems.
Investigations on mixed-gas plasmas produced by adding nitrogen to the plasma gas in ICP-MS
Spectrochimica Acta Part B: Atomic Spectroscopy, 1991
Ahstraet-Additions of nitrogen were made to the argon plasma gas of an inductively coupled plasma (ICP) used as an ion source in mass spectrometry (MS). The studies were carried out at constant nebulizer gas flow rate and uptake rate (i.e. constant nebulization efficiency), with the percentage of nitrogen in the plasma gas (from 0 to 10%) and the power (from 1.0 to 1.4 kW) as the only variables. For each set of operating conditions, the analytical characteristics were assessed for %Fe+, Te+, 76Se+ and 'YGe+. The best results were obtained at 1.2 kW where, although the sensitivity was reduce.d by a factor of up to 5 upon addition of nitrogen to the plasma, the stability of the plasma was improved, resulting in similar (Se) or improved (Fe) detection limits, by up to a factor of 4. A study of the effect of a matrix containing up to 0.1 M Na was also carried out (at 1.2 kW) while the percentage of nitrogen in the plasma gas was raised from 0 to 10%. The results show that the non-spectroscopic interference of Na can be reduced. In fact, with 5% nitrogen in the plasma gas, the effect of 0.01 M Na was essentially eliminated. Furthermore, the accuracy and precision of the 57Fe+/56Fe+ and TSe+P*Se+ isotopic ratios were found to improve as the amount of nitrogen was increased. For instance, the precision of the mean 57Fe+P6Fe+ ratio measured in solutions containing from 0 to 0.1 M Na improved by an order of magnitude with 10% nitrogen in the plasma, and that of 76Se+ESe+ improved by a factor of 4, which is still quite significant, given the high 76Ar+ background in comparison with the relatively low abundance of "Se+. Overall, the results suggest that an Ar-N, mixed-gas plasma may be a better ion source for MS than an all argon ICP.