The use of discharge lamps as directly modulated atom reservoirs for selective line modulation in atomic emission spectrometry

A simple method is described for selectively modulating the atomic or ionic resonance lines emitted by an excitation source. A modified discharge lamp with a cylindrical hollow cathode is used to generate a modulated atom cloud. The emission from the excitation source is then imaged through the modulated atom cloud within the cylindrical cathode lamp, to yield a selectively modulated signal. The ability of the system to reduce spectral interferences in inductively-coupled plasma emission spectrometry is assessed and discussed.     

Evaluation of an inductively-coupled plasma with an extended-sleeve torch as an atomization cell for laser-excited fluorescence spectrometry

An inductively-coupled plasma (ICP) with an extended-sleeve torch has been evaluated as an atomization cell for laser-excited fluorescence spectrometry. Limits of detection for 20 lines are given. The detection power is almost equivalent to that obtained by excitation with a hollow-cathode lamp. Interelement effects and spectral interferences are discussed.     

Laser excited atomic fluorescence of some transition elements in the nitrons oxide-acetylene flame

A pulsed, tunable dye laser, pumped with a nitrogen laser is used to excite the atomic fluorescence of Sc, V, Hf, Nb, Os, Zr, W, Rh and Ru. Except in the case of Rh, the nitrous oxide-acetylene flame has been used. The results obtained for Zr and W are due to scattering of the laser radiation from unvaporized particles in the flame. Since, for most elements, several fluorescence lines of comparable intensity have been observed after the primary excitation process, the usefulness of observing non-resonance fluorescence is stressed, particularly with regard to the possibility of minimizing spectral interferences. The experimental results demonstrate that the limits of detection obtained with the dye laser source are comparable or better than the best atomic absorption limits only when the same primary absorption line used for the atomic absorption measurements can be used for exciting the fluorescence.     

Use of a large quartz spectrograph for the determination of thorium, yttrium and the rare earths in silicates

Studies were carried out on the optimum conditions for the successful use of a large quartz spectrograph for the determination of thorium, yttrium and the rare earths in silicate rocks. The best line-to-background ratios were achieved by arcing samples in a matrix of 4 % sodium chloride in carbon powder. An atmosphere of 20 % argon and 80% oxygen was used to reduce background and eliminate cyanogen band interference. An anion-exchange procedure was used to separate the rare earths from other elements. The resultant enrichment allowed use to be made of less sensitive rare earth lines in the ultraviolet end of the spectrum where the spectrographic dispersion is greater. Line interferences were studied and necessary corrections for these interferences were calculated. The technique was tested by analysing the standard rocks, G-1, W-1 and CAAS syenite. Good agreement with recommended values was obtained.     

Matrix effects of easily ionizable elements and nitric acid in high-power microwave-induced nitrogen plasma atomic emission spectrometry

Matrix effects of Na, Ca and nitric acid in high-power microwave-induced nitrogen plasma atomic emission spectrometry were investigated with a number of atomic and ionic lines covering a wide range of energies. The plasma was sustained in an Okamoto cavity at atmospheric pressure by using nitrogen as the plasma gas as well as the nebulizer gas. Most of the atomic lines tested exhibited enhancement effects and all of the ionic lines gave suppression effects in the presence of Na and Ca. The effects decreased with increasing microwave power. There was good correlation between matrix effects, the excitation energy and energy sum of the spectral lines. The lower the excitation energy for atomic lines and the higher the energy sum for ionic lines, the stronger the matrix effects. Unlike Na and Ca, nitric acid showed suppression effect for all of the spectral lines and the effect was independent of the energy of the spectral lines and the microwave power. The effect of matrix on the excitation temperature and the electron number density was measured and the mechanism of matrix effect was discussed.     

Cathode-ray-excited emission spectroscopic analysis of trace rare earths: Part I. Qualitative studies

Line emissions from f-f transitions in rare earths contained in a matrix are obtained by excitation with cathode rays. The distinctive energy of these emissions is utilized to detect the presence of trace amounts of rare earths, and non-destructive identification of such traces is carried out quickly by comparison with a derived hauptlinien spectrum. Matrix effects, masking interferences and the utilization of line shape are discussed.     

Effect of radiofrequency power on laser induced fluorescence and emission spectrometry with an extended-sleeve inductively-coupled plasma torch

Relative laser-excited fluorescence and emission intensities as a function of RF power were measured for the Ca-I, Ca-II, Ba-I, Ba-II, Mg-I, Mg-H, Na-I and Cu-I lines with an extended inductively-coupled plasma (ICP) torch. In most cases, the relationships were different from those found in previous studies with a conventional short ICP torch. In some cases, unexpected double maxima or minima occurred. A study of the effect of an easily ionized element, potassium, on the fluorescence at the Ca-I and Ca-II lines with the extended-sleeve torch showed a considerably larger ionization interference than exists with the conventional short torch. The extended torch has found some use in laser-excited fluorescence and ICP-excited fluorescence, but researchers should be wary of unexpected variations with power and substantial ionization interferences.     

Influence of hydrogen gas over the interference of acids in inductively coupled plasma atomic emission spectrometry

The effect of hydrogen gas on the plasma and its influence on acid interferences in plasma atomic emission spectrometry was studied. The study was performed with HCl and HNO₃ in the concentration range of 0–2 mol l⁻¹. Vanadium and magnesium were used as test elements, the study was extended to other several elements. The effects of hydrogen gas on the plasma were studied by measuring excitation temperature, electron number density and the ionic-to-atomic line intensity ratio. The net effect of hydrogen was an increase in electron density and ionic to atomic line intensity ratio. A small increase in the excitation temperature was observed. The signal suppression for ionic lines causes by mineral acid was reduced when small amounts of hydrogen was introduced into the plasma as sheathing gas. This effect was attributed to the increase in plasma electron density.     

Time-resolved measurement of copper emission spectrum excited by a low-pressure argon laser-induced plasma.

A laser-induced plasma generated with a pulsed Nd:YAG laser under evacuated conditions has complicated structures both temporally and spatially. The time-resolved spectra of copper in three different wavelength regions were observed in detail for elucidating the excitation mechanisms of many atomic/ionic copper emission lines. The emission intensities of copper emission lines, measured in a time-resolved mode, were strongly dependent on the kind of copper lines: ionic or atomic lines, and their excitation energies. Generally, copper ionic lines were rapidly decayed and dominantly emitted from the initial breakdown zone, because the copper ions requiring larger excitation energies were produced mainly in the hot breakdown zone. On the other hand, the atomic lines were emitted during prolonged periods, implying that they could also be excited in the expanded plasma zone. The excitation phenomena occurring in the laser-induced plasma could be better understood by analyzing the time-resolved copper spectra.     

Analytical characteristics of near-infrared nonmetal atomic emission from a helium microwave-induced plasma

Relative emission intensities for several atomic lines of C, N, O, F, S, Cl and Br between 700 and 1200 nm in an atmospheric-pressure helium microwave-induced plasma are reported. For each element the most intense near-infrared lines are compared to the most intense u.v.-visible lines in terms of signal-to-background ratios and spectral interferences. The relative-intensity data are used to calculate excitation temperatures for each element.     

Spectral interferences in the determination of traces of scandium, yttrium and rare earth elements in “pure” rare earth matrices by inductively coupled plasma atomic emission spectrometry: Part VII — Terbium, Dysprosium, Holmium and Thulium

This article is the seventh part of a series of papers discussing the spectral interferences of rare earth elements (REEs) in ICP-AES. Radial viewing 27.12 MHz inductively coupled plasma atomic emission spectrometry (ICP-AES) was used in the determination of scandium, yttrium and rare earth elements in Tb₂O₃, Dy₂O₃, Ho₂O₃ and Tm₂O₃ as “pure” rare earth matrices. The quantification of the interferences in terms of Q-values for line interference Q_I(_a) and wing background interference Q_W(Δλ_a) were used in accordance with Boumans and Vrakking [Spectrochim. Acta Part B 43 (1988) 69]. The “best” analysis lines from point of view of spectral interferences were selected. The true detection limits by using the “best” analysis lines were calculated.     

Determination of rare-earth elements,yttrium and scandium in manganese nodules by inductively-coupled argon-plastma emission spectrometry

A sequential-scanning, inductively-coupled argon plasma emission spectrometer is used for the determination of the rare-earth elements, plus yttrium and scandium, in manganese nodules. Wavelength selection is optimized to minimize spectral interferences from manganese nodule components. Samples are decomposed with mixed acids in a sealed polycarbonate vessel, and elements are quantified without further treatment. Results for U.S. Geological Survey manganese nodule standards A-1 and P-1 had average relative standard deviations of 6.8% and 8.1%, respectively, and results were in good agreement with those obtained by other methods.     

Simultaneous determination of 14 lanthanides and yttrium in rare earth ores by inductively-coupled plasma atomic emission spectrometry

A method is described for simultaneous determination of 14 lanthanides and yttrium in monazites and xenotimes by inductively-coupled plasma atomic emission spectrometry. The ore samples were decomposed by heating with nitric acid/perchloric acid or hydrofluoric/nitric/perchloric acids, or sulfuric acid, or by fusion with sodium carbonate. Among these methods, treatment of the samples with sulfuric acid, by evaporation to dryness followed by dissolution of the residue with hydrochloric acid is recommended; it provided complete decomposition for the five monazites and xenotimes examined. The accuracy and precision of the results were significantly influenced by spectral interferences of the rare earth elements themselves; correction methods and factors are given. The chondrite-normalized rare-earth patterns were examined to characterize the monazite and xenotime samples.     

Laser induced double-resonance ionic fluorescence in an inductively coupled plasma

Two pulsed dye lasers pumped by an excimer laser are simultaneously directed into the analytical zone of an inductively coupled argon plasma. When the two beams are tuned to the appropriate ionic transitions, highly excited ionic levels can be efficiently populated in saturated conditions, the resulting fluorescence being then spectrally isolated with a monochromator and measured. A theoretical outline of this technique, variously called double-resonance fluorescence or two-step fluorescence, is given. The experimental results obtained with the alkaline-earth metals Ca, Sr, Ba and Mg show that the technique does provide excellent sensitivity, freedom from scattering problems and unprecedented spectral selectivity. The laser characteristics, the time overlap between the pulses and the spectral characteristics of the transitions used are discussed. Finally, ionic fluorescence in the plasma is the most suitable analytical application of such double-resonance technique since its use in flame atomic fluorescence suffers from the strong depletion of the excited levels due to collisionally assisted ionization.     

An ICP-excited ICP resonance monochromator and fluorescence spectrometer for the analysis of trace to major sample constituents

A 20 solution of the element of interest is aspirated into a 1500 W Ar ICP and the resulting emission is used to excite atomic and ionic fluorescence of a sample aspirated into a second ICP. Detection limits are comparable to ICP-AES. By aspirating the sample into the source ICP and measuring its emission using the second plasma as a resonance monochromator, linear dynamic ranges up to 5 × 10⁷ can be achieved. Plasma emission background and spectral interferences are minimal compared to ICP-AES because of the selectivity of the fluorescence technique. The present system should be considered as a viable alternative to emission spectrometry in order to alleviate spectral interferences which may occur in complex sample matrices, without the need for an expensive, high resolution monochromator.     

Selective excitation of singly-ionized silver emission lines by Grimm glow discharge plasmas using several different plasma gases

The relative intensities of silver emission lines from Grimm glow discharge plasmas were investigated in the wavelength range from 160 to 600 nm when using different plasma gases. It was characteristic of the plasma excitation that the spectral patterns were strongly dependent on the nature of the plasma gas employed. Intense emission lines of silver ion were observed when argonhelium mixed gases were employed as the plasma gas. Selective excitation of the ionic lines could be principally attributed to the charge transfer collisions between silver atoms and helium ions.     

碱金属、碱土金属氯化物对稀土谱线强度的影响

本文研究了碱金属、碱土金属氯化物载体对稀土谱线强度的影响。实验结果表明,加入这些载体后,由于等离子区稀土原子数增加,能大大提高稀土谱线强度,其效果原子线大于离子线,所用载体中以选用NaCl、KCl、CsCl为宜。     

Ionization interferences under various operating conditions in a 9, 27 and 50 MHz ICP,and a study of shifts in level populations of calcium through simultaneous absorption-emission measurements in a 9 MHz ICP

Radially resolved absorption and emission measurements were employed for a better understanding of the excitation mechanism of nebulized species operating under conditions favourable for the occurrence of ionization interferences in an atmospheric pressure 9 MHz ICP. Three monitored spectral lines of calcium were used to observe changes in ground and excited level populations of atoms and ions, in ion excitation temperatures using the two-line method. Observations were made at a fixed height, namely 25 mm above the rf coil and varying carrier gasflows from 2 to 51 min^?1 and were correlated with the position of the “initial radiation zone” (IRZ) in the plasma. Ionization interferences occurring only inside the IRZ indicate an excitation mechanism depleting ion ground level population and populating excited atom and ion levels. No changes in atom absorbances or excitation temperatures were observed ruling out ionization suppression as dominating mechanism. Indications are that increased collisional excitation for Ca ions and ambipolar diffusion may be the dominant excitation mechanism operating in the analyte channel. Recombination reactions (three body or radiative) or charge transfer reactions may be responsible for an increase of excited atom level populations. It is obvious that non-thermal processes are operating under conditions favourable for ionization interferences occurring in the ICP.     

Spectral interferences in the determination of traces of scandium, yttrium and rare earth elements in “pure” rare earth matrices by inductively coupled plasma atomic emission spectrometry. Part IV. Lutetium and yttrium

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), a section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by an electronic archive, stored on the SAE homepage at http://www.elsevier.nl/locate/sabe. The archive contains data files and text files. The present article is the fourth part of a series of papers discussing the spectral interferences of rare earth elements (REEs) in inductively coupled plasma atomic emission spectrometry (ICP-AES). The spectral interferences for 200-pm wide windows centred (±100 pm) around the prominent lines of the analytes, due to matrix lines and oxide radicals (LuO or YO) that emit band spectra depending on the excitation temperature (T_exc.) in ICP were investigated. The main result is that for T_exc.=7200 K, LuO and YO band components can be eliminated so that prominent analysis lines of La, Ce, Pr, Nd, Eu and Sm were observed on a smooth background. T_exc..=7200 K was chosen as the optimal excitation temperature in the determination of traces of REEs in Lu₂O₃ and Y₂O₃, respectively. The quantification of the interferences in terms of Q-value was used in accordance with Boumans and Vrakking [Spectrochimica Acta Part B 42 (1987) 819; 43 (1188) 69]. The “best” analysis lines are free of line interferences and negligibly influenced by wing interferences and Lu₂O₃ and Y₂O₃ as matrices do not raise the real detection limits.     

Simultaneous determination of boron,phosphorus and sulphur in some biological and soil materials by inductively-coupled plasma emission spectrometry

Atomic emission lines at 249.678 nm, 214.911 nm and 180.735 nm are used simultaneously to determine total concentrations of boron, phosphorus and sulphur respectively, in plant and soil sample digests by means of inductively-coupled plasma emission spectrometry. The digestion procedures chosen enable these elements to be determined simultaneously on a single digest. Analytical data are compared after using various digestion procedures on standard reference materials. Actual and potential interelement interferences in the plasma are discussed together with attempts to overcome these interferences. Limitations for simultaneous determinations of boron, phosphorus and sulphur remain in the digestion and dissolution procedures.