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—II: Praseodymium and samarium

This paper is the second part of a series of papers dealing with mutual spectral interferences of rare earth elements (REEs) in inductively coupled plasma atomic emission spectrometry (ICP-AES). The present article covers: (a) the spectral data of praseodymium and samarium interferents for 200 pm wide windows centred (± 100 pm) about prominent lines of scandium, yttrium and REEs; (b) the data base of Q values for line interference (Q₁) and Q values for (wing) background interference (Q_w); and (c) the detection limits measured by using the “true detection limit” criterion as proposed by Boumans and vrakking [Spectrochim. Acta 42B, 819 (1987); 43B, 69 (1988)]. The lines with the lowest values of true detection limits for praseodymium and samarium matrices were chosen for analysis. This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by a disk with data and text files. The data files comprise in particular the tabular material of this article in electronic form.     

An electronic spectroscope for classroom displays of visible spectra

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 program, data and text files. The hardcopy text describes a program that has been developed to accept data from a compact electronic spectrograph and translate the data into a display on a computer screen. The computer display mimics the view seen through a direct vision spectroscope. Atomic spectra appear as vertical lines of the appropriate color dispersed on a black field. A conventional plot of intensity versus wavelength is simultaneously displayed. The update of the display is sufficiently rapid that the image on the screen is essentially a real-time representation of the light entering the spectrograph. The system was designed for use in conjunction with video projection equipment in demonstrations to large groups of students.     

An electronic aid for line selection for scanning inductively coupled plasma atomic emission spectrometers

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). Accompanying this hard copy text is a disk containing the program, source flies, data files and a brief manual along with a few programming notes. The main article discusses the purpose of this work, and the Appendix provides brief instruction on the use of the program, manipulation of the data, and source code. An automatic file selection system for the control of a rapid scanning spectrometer performing atomic emission spectrometry has been developed using the PROLOG language. The system can be “taught” the elemental composition of a given sample type. It uses this information (when available) to generate a linear search strategy which minimizes the number of lines that need to be measured. The rules used by the system can be observed during system operation to allow a trace of the logic. Reading of the initial data base takes no more than 6 s and then decisions are made in less than 1 s per line.     

Computer modeling of fluorescence dip spectroscopy with pulsed laser excitation

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hard copy text is accompanied by a disk with a demonstration program, block libraries, demonstration files, and ancillary files. The article discusses the computer modeling of fluorescence dip spectroscopy, a relatively new and powerful atomic diagnostic technique. The models were found to agree essentially perfectly with previously published photostationary results and to extend those results to the more realistic laser temporal profiles encountered in actual experiments.

The fluorescence dip parameters were found to be robust so long as the system under study approached saturation conditions. Short, noisy laser pulses were found to be acceptable, for determination of the fluorescence dip parameters, provided the laser pulses were sufficiently intense to cause near saturation of the three level system. Conversely, steady state excitation was not found to be crucial to the determination of accurate fluorescence dip parameters. For a five level model of the silver atomic system, “negative fluorescence dips” were readily found in the simulations, even though some of the relevant parameters were rough estimates of the actual, unknown parameters.     

MS Interview: An elemental mass spectrometry spectral interference data base

A graphically-oriented data base of spectral interferences dut occur in inductively coupled plasma-mais spectrometry and glow discharge-mass spectrometry has been developed. The program is called “MS Interview” and runs on a Macintosh computer. The program allows one to specify which technique (ICP or GD) the various interferences will be presented for, and for the case of the ICP, the acid matrix background. Bated on these parameters the program provides a listing of interferences broken down into the following categories: Isobarics, Oxides, Doubly Charged Species, Background Dependent, and Matrix Dependent. For the glow discharge case there are two additional categories: Argides and Dimers. Interference information is provided for all masses of all elements and is easily accessed via mouse operations from a periodic table window and element mass spectral windows. The program is expandable to include other ion sources and interferences can be added or deleted as required by the user. Finally, the program also includes a small library of typical background spectra that can be displayed and manipulated. This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta B (SAB). The hardcopy text is accompanied by a disk containing the program MS Interview, a manual, a reference list, and a bar graph format mass spectral library of the elements.     

Simulation of atomic spectra—II. Mutual spectral interferences of rare earth elements in the inductively coupled plasma

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta B (SAB). The hardcopy text, comprising the main article and an appendix, is accompanied by a diskette with a program, data files, and a manual. The text details the purpose of the work, with emphasis on the spectroscopic aspects, and the appendix provides the essential information for accessing the diskette and using program and data. Additional tutorial guidance is provided by the manual.

The program primarily concerns the simulation of the spectra of rare earth elements (REE) as interferents in 80-pm wide spectral windows centred about the wavelengths of 26 prominent lines of Ce, La, Nd, Pr, and Sm. The program essentially covers the model described in Spectrochim. Acta 43B, 1365 (1988) and the database is identical to the experimental database published in Spectrochim. Acta 44B, 31 (1989). Accordingly, the data are for an inductively coupled plasma (ICP). The program enables the user to simulate spectra with the spectral bandwidth as an optional variable. The user may then generate spectra of both single REEs, without or with analyte, and mixtures of REEs of any composition, also without or with analyte, whereby for spectra with analyte the display includes the blank spectrum. Displays are accompanied by legends providing a set of essential numerical data. In addition, particular program options allow the generation of numerical data only, one of them being the calculation of true detection limits. This option permits it to perform, within the limited scope of the database, line selection for complex REE samples in a rational way.

The program operates, in principle, with the default values of the ICP Doppler temperature (6800 K) and “average” ICP a-parameter of the Voigt profile (0.5), but these values may be optionally modified. Similarly, the user may add new data files to the base and thus also apply the program for other purposes and outside the REE environment, such as model studies in general, and for learning or teaching, as explained in the manual on the diskette. The tutorial part of this manual provides the user not only with elementary instructions for using the program as a practical tool, but also incorporates a variety of instructive examples, including a brief “course” on spectral line profiles and spectral interferences.     

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-I. Cerium, neodymium and lanthanum matrices

The present paper deals with spectral interferences from cerium, neodymium and lanthanum on prominent lines of scandium, yttrium and rare earth elements (REE). The “true detection limit” criterion was used for rational wavelength line selection as proposed by boumans and vrakking [Spectrochim. Acta 42B, 819 (1987); 43B, 69 (1988)]. Analysis lines selected for cerium and neodymium matrices suffered both wing and line interferences. In the case of a lanthanum matrix, it is possible to choose mostly analysis lines that are free of line interference and negligible wing interference. The high degree of spectral interferences with a cerium or neodymium matrix significantly worsens the true detection limits. This article is an electronic publication in Spearochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by a disk with data and text files. The data files comprise in particular the tabular material of this article in electronic form.     

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.     

Tomographically resolved ionization temperatures and electron densities in the inductively coupled plasma determined by the line-to-continuum method

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by three disks with data files with the hardcopy paper in Word 5.0 and ASCII format, and a disclaimer. The text details the purpose of the work and the structure of the three-dimensional Ar ionization temperature and electron number density data files. The line-to-continuum method was used to evaluate the spatial distribution of Ar ionization temperatures, T_ion, and electron number densities, n_e, within a dry Ar inductively coupled plasma (ICP). The emission measurements were spatially resolved in three dimensions by reconstruction algorithms for computed tomography. The 40.68 MHz Ar ICP was operated at applied r.f. power levels of 0.75 and 1.0 kW. The reconstructed distributions of Ar I line emission (430.0 nm) and continuum emission (428.6 nm) show good reproducibility over a series of five replicate runs. Argon ionization temperatures remain within a 6500–8500 K range throughout the continuum-emission cone of the plasma. Deviations from this temperature range occur in the central channel and around the outer edge of the plasma. Low in the plasma, the central-channel T_ion is cooler than 6000 K. Along the outer edge of the plasma, the line-to-continuum ratio becomes small; this low ratio results in erroneously high temperatures (> 12000 K). The errors in T_ion appear to be due to reproducible artifacts in the reconstruction process that lead to low Ar I line-emission readings along the outer edge of the plasma. Electron densities show a maximum of 8.5 × 10¹⁴ cm⁻³ and 1.2 × 10¹⁵ cm⁻³ at 0.75 and 1.0 kW, respectively. Electron number densities were much better behaved than T_ion due to their dependence on the square-root of continuum measurements and only the fourth-root of T_ion.     

A computer program for the collection,reduction and analysis of echelle spectra

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text, comprising the main article and an appendix, is accompanied by a disk containing the compiled program, a manual, the source code and tutorial in ASCII format, and data files. The work presented is a result of the need to facilitate collection, calibration, and extraction of data from an echelle spectrometer employing charge coupled array detection (CCD). A computer program, written using Microsoft's BASIC Professional Development System version 7.1 under MS DOS, is explained and demonstrated. Wavelength calibration requires critical spectrometer dimensions, grating counter settings, and the identification of a single spectral line. Calibration accuracies are better than ± 1 pixel across a 576 × 384 pixel array. Extraction of intensity-normalized spectra for all detected orders requires less than 3 min on a 33 MHz 80386 personal computer with an 80387 math coprocessor.     

Methods of calibration in the direct analysis of solid samples by electrothermal atomic absorption spectrometry

One of the major problems involved in the direct analysis of solid samples by electrothermal atomic absorption spectrometry (ETAAS) lies in the calibration step because non-spectral interference effects are often pronounced. Three standardization techniques have been described and used in solid sampling-ETAAS: (i) standard additions method; (ii) calibration relative to a certified reference material; and (iii) calibration curve technique. However, an adequate statistical evaluation of the uncertainty in the analyte concentration in the solid sample is most frequently neglected, and reported errors may be seriously underestimated. This can be attributed directly to the complexity of the statistical expressions required to accurately account for errors in each of the calibration techniques mentioned above, and the general lack of relevant reference literature. The object of this work has been to develop a computer package which will perform the necessary statistical analyses of solid sampling-ETAAS data; the result is the program “SOLIDS” described here in the form of an electronic publication in Spectrochimica Acta Electronica, the electronic section of Spectrochimica Acta Part B. The program could also be useful in other analytical fields where similar calibration methods are used. The hard copy text, outlining the calibration models and their associated errors, is accompanied by a diskette containing the program, some data files, and a manual. Use of the program is exemplified in the text, with some of the data files discussed included on the diskette which, together with the manual, should enable the reader to become familiarized with the operation of the program, and the results generated.     

MSGRAPH: A program for the display of LC/MS data

The analysis of mixtures of unknowns using techniques interfacing liquid chromatography (LC) with mass spectrometry (MS) often suffers from the high abundance of background ions. To allow a quick search for components in the mixtures, a special type of display has been developed that shows all the data obtained in an analysis run simultaneously. On the screen, the m/z information from the mass scan (in the x direction) and the time (as scan number, in the y direction) are displayed with mass peaks given as single points. The relative intensity of a signal is colour coded. Thus, it is easy to recognize analyte signals as bright islands in a dark surrounding; even weak signals in the vicinity of strong background ions are identified quite clearly. Additionally, the program incorporates some features to allow a simple operation and very fast investigation of the data. This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by a disk containing the program MSGRAPH, a manual, data files and additional text files.     

A LabVIEW® program for determining electron number density from Stark broadening measurements of the hydrogen-beta line

A useful plasma diagnostic is the measurement of electron number density. One way to accomplish such measurements is to determine the contribution to the broadening of a spectral line due to the Stark effect. To simplify and extend such electron density measurements across computer platforms, a program that calculates electron number density from the Stark-broadened hydrogen-beta line has been written for the LabVIEW^® environment. This program calculates electron number densities from the field strength that would be exerted on a hydrogen atom immersed in a plasma. Using the new program, the electron number density in a glow discharge is calculated for two different operating conditions. Not surprisingly, the results indicate that to increase the current density in the discharge, the source electrodes must be reduced in surface area. This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by one disk with an executable program (written for Apple Macintosh), data and text files including a manual.     

IDAS: a Windows based software package for cluster analysis

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text, comprising the main article and one appendix, is accompanied by two installation diskettes with the software package and data files. The main article discusses the chemometric aspects of the package and explains its purpose.The IDAS software package combines three cluster analysis methods (hierarchical, non-hierarchical and fuzzy) and runs under MS Windows. Modified algorithms for non-hierarchical and fuzzy clusterings are described. The interpretation of the clustering results is facilitated by the extensive use of different types of graph. New approaches to the graphical representation of the results of fuzzy clustering are proposed.Two data sets, the Iris data by Fisher and a data set on the chemical composition of tea, are used to demonstrate the capabilities of the software.     

DensMat: fully time-resolved simulation of two-step pulsed laser excitation of atoms in highly collisional media

A program that simulates and displays the level populations of atomic systems exposed to dual-wavelength (i.e. two-colour) pulsed laser excitation in highly collisional media (such as flames and plasmas) has been developed. The program is based upon a previously published fully time-dependent density-matrix model that describes step-wise excitations of atoms with degenerate states under collision-dominated conditions, and which thus goes beyond the rate-equations formalism. This model can predict such phenomena as Rabi flopping and a.c.-Stark splitting, shifting and broadening. The program can be used as a prediction tool for laser-enhanced ionization, laser-induced fluorescence, fluorescence dip spectroscopy and other two-colour laser-based spectroscopic experiments. The program provides the user with a flexible four-level atomic system, configurable as a one- or two-step excitation ladder, along with an ionization continuum and non-laser-connected level(s) that may act as trap(s) or metastable level(s). Parameters such as level degeneracy, collisional rates and laser pulse widths, shapes, wavelengths, intensities and bandwidths are accessible to the user. The program can display both the time development of the level populations and also level populations versus laser wavelength. This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by a disk containing the program DensMat, an associated on-line help file and manual, an installation program, and data files pertaining to the examples illustrated in this article. The program runs under Windows 3.1 on an IBM-compatible computer.     

Digital video clips for improved pedagogy and illustration of scientific research — with illustrative video clips on atomic spectrometry

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 CD-ROM accompanying this issue. The archive contains video clips. The main article discusses the scientific aspects of the subject and explains the purpose of the video files. Short, 15–30 s, digital video clips are easily controllable at the computer keyboard, which gives a speaker the ability to show fine details through the use of slow motion. Also, they are easily accessed from the computer hard drive for rapid extemporaneous presentation. In addition, they are easily transferred to the Internet for dissemination. From a pedagogical point of view, the act of making a video clip by a student allows for development of powers of observation, while the availability of the technology to make digital video clips gives a teacher the flexibility to demonstrate scientific concepts that would otherwise have to be done as ‘live’ demonstrations, with all the likely attendant misadventures. Our experience with digital video clips has been through their use in computer-based presentations by undergraduate and graduate students in analytical chemistry classes, and by high school and middle school teachers and their students in a variety of science and non-science classes. In physics teaching laboratories, we have used the hardware to capture digital video clips of dynamic processes, such as projectiles and pendulums, for later mathematical analysis.     

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 III. Europium

This paper is the third part of a series of papers dealing with spectral interferences of rare earth elements (REEs) in inductively coupled plasma atomic emission spectrometry (ICP-AES). The present article shows: (a) the spectral data of europium interferent for 200 pm wide windows centred (±100 pm) about prominent lines of scandium, yttrium and REEs; (b) the database of Q values for line interference (Q_l) and Q values for (wing) background interference (Q_w); (c) the detection limits measured by using the “true detection limit” criterion as proposed by P.W.J.M. Boumans and J.J.A.M. Vrakking (Spectrochim. Acta Part B, 42 (1987) 819; 43 (1988) 69). Different possibilities for improvement of the true detection limits are discussed: the use of equipment of high resolving power, the application of multicomponent analysis (MCA) techniques and preliminary separation of the matrix component combined with preconcentration of trace REEs. This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hard copy text is accompanied by a disk with data and text files. The data files comprise in particular the tabular material of this article in electronic form.     

Signal processing of transient atomic absorption signals

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hard copy text is accompanied by a disk with a demonstration version of the simulation program, libraries of electronic and optical component blocks, simulation models, manual, and other files.Absorbance signals for electrothermal atomization atomic absorption spectroscopy (ETA-AAS) were generated digitally and the effect of various types and sources of noise upon the precision of the absorbance measurement was evaluated by numerical calculation. Peak area measurement, peak height measurement, and matched filtering were used for processing these signals. The performance of these three techniques in the presence of various types of noises and the sensitivity of each to small variation in the atomization conditions was calculated. It is demonstrated that significant improvement in signal-to-noise ratios can be realized by application of appropriate signal processing methods. The results also indicate that one of the principal causes for loss of precision could be the variation in the heating characteristics of the furnace.     

Computer expert system for spectral line simulation and selection in inductively coupled plasma atomic emission spectrometry

This paper is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta, Part B (SAB). This hardcopy text, comprising the main body and an appendix, is accompanied by a disk with programs, data files and a brief manual. The main body discusses purpose, design principle and usage of the computer software for the inductively coupled plasma atomic emission spectrometry (ICP-AES) expert system. The appendix provides a brief instruction on the manipulation of the demonstration program and relevant information on accessing the diskette.The computer software of the expert system has been developed in C++ language to simulate spectra and to select analytical lines in ICP-AES. This expert system is based on a comprehensive model of non-LTE ICP-AES, which includes expertise in plasma discharges, analyte ionization and excitation, and spectral-line shapes. The system also provides several databases in which essential elemental and spectral data are stored. A logic reasoning engine is utilized for selection of the best analytical line with a main criterion of minimizing the true detection limit. The system is user-friendly with pop-up menus, an editor for database operation, and a graphic interface for the display of simulated spectra. The system can simulate spectra and predict spectral interferences with good accuracy.     

Spectral interferences in the determination of trace elements in environmental materials by inductively coupled plasma atomic emission spectrometry

This paper deals with spectral interferences in inductively coupled plasma atomic emission spectrometry (ICP-AES) encountered with environmental materials. These samples normally contain high concentrations of aluminium, calcium, magnesium, iron, titanium, potassium and sodium. The investigations cover: (a) spectral data for Al, Ca, Mg, Fe, Ti, K and Na as interferents for 200 pm wide windows centred (±100 pm) around the prominent lines of As, B, Ba, Be, Cd, Cr, Cu, Hg, Mn, P, Pb, Sb, Se, Sn, Tl, U and Zn; (b) a data base of Q-values for line interference [Q_Ij(λ_a)] and Q-values for wing background interference [Q_Wj(Δλ_a)] for two values of the excitation temperature 6200 K and 7200 K. The lines free or negligibly influenced by line interference were selected for analyte determination. Q-values were used for calculation of correction factors under a spectral line without the measurement of a reference blank at the wavelength of the prominent analysis lines. The accuracy of ICP-AES with the Q-concept as a basic methodology is checked by the analysis of a certified reference material IAEA/Sediment SD-N-1/2/. The precision of the method is characterised by an RSD of 0.6–1.7%. Extraction of trace elements soluble in aqua regia was used as a decomposition method. 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 the tabular material of this article in electronic form.