Simultaneous multielement analysis

Multielement flame emission spectroscopy is a relatively new development, although multielement methods have been used in arc-spark emission spectroscopy for some years. Several multielement methods are available, including scanning, direct reading techniques similar to those employed in arc-spark emission spectroscopy and the more recently developed vidicon detector tubes. Vidicon detectors are described in Chapter 3. 

Mitchell et al described the use of a vidicon detection system to permit the simultaneous determination of up to ten elements in solution. They used an 0.25-m monochromator and covered a wavelength range of 1680 A displayed across the face of the vidicon detector. Spectral lines as close as 20 A were readily resolved. 

FIGURE 9-14. Multielement flame emission spectrum from 3886 to 4086 A. [From K. W. Busch, N. G. Howell, and G. H. Morrison, The Vidicon Tube as a Detector for Multielement Flame Spectrometric Analysis, Anal. Chem., 46, 575 (1974). Used by permission of the American Chemical Society.] 

An optical multichannel analyzer was used to obtain both peak height and peak area and was corrected for background. Results indicate either peak height or peak area can be used analytically except under electronic overload conditions. The method was used with a U. S. Geological Survey rock sample to determine Al, Fe, Ca, and Ti. The multielement technique compared favorably with concentrations of the four elements as reported by the U. S. Geological Survey. 

FIGURE 9-15. Flame emission signals of manganese standards (4032 A). [From W. G. Schrenk, in Flame Emission and Atomic Absorption Spectroscopy, Vol. 2, Edited by J. A. Dean and T. C. Rains, Marcel Dekker, New York (1971), Chapter 12. Used by permission of Marcel Dekker Inc.] 

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G. M. Levy, A. Quaglia, R, E. Lazure, and S. W. McGeorge. Spect. Acta. 42B, 341, 1987. Describes the diode array-based spectrally segmented spectrometer for simultaneous multielement analysis. 

N. Jakubowski, D. Stuewer and W. Vieth, Performance of a glow discharge mass spectrometer for simultaneous multielement analysis of steel, Anal. Chem., 59 (1987) 1825-1830. 

Unlike a flame, in which only a very limited number of metals emit light because of the low temperature, virtually all metals present in a sample emit their line spectrum from the ICP torch. Not only does this make for a very broad application for ICP, but it also means that a given sample may undergo very rapid and simultaneous multielement analysis. With this in mind, it is interesting to consider the options for the optical path for the ICP instrument. 

The advantage of ICP is that the emissions are of such intensity that it is usually more sensitive than flame AA (but less sensitive than graphite furnace AA). In addition, the concentration range over which the emission intensity is linear is broader. These two advantages, coupled with the possibility of simultaneous multielement analysis offered by the direct reader polychromator design, make ICP a very powerful technique. The only real disadvantage is that the instruments are more expensive. See Workplace Scene 9.3. 

L. Ebdon, M. Foulkes and K. O Hanlon, Optimised simultaneous multielement analysis of environmental slurry samples by inductively coupled plasma atomic emission spectrometry using a segmented array charge-coupled device detector. Anal. Chim. Acta, 311, 1995, 123-134. 

The inductively coupled plasma13 shown at the beginning of the chapter is twice as hot as a combustion flame (Figure 21-11). The high temperature, stability, and relatively inert Ar environment in the plasma eliminate much of the interference encountered with flames. Simultaneous multielement analysis, described in Section 21 1. is routine for inductively coupled plasma atomic emission spectroscopy, which has replaced flame atomic absorption. The plasma instrument costs more to purchase and operate than a flame instrument. 

The FAAS method offers similar detection limits to NAA and is suitable for the determination of low levels of lead. Equipment costs are reasonable and the instrumentation is commonplace in many analytical laboratories. A large number of metallic elements, over a wide concentration range, extending down to ultra-trace level, can be analyzed, thus making the technique versatile and useful for other forensic applications as well as FDR detection. Apart from cost, the main advantages are simplicity, speed of analysis, and in house operation. One disadvantage of FAAS is that it is not capable of simultaneous multielement analysis. 

Contamination of the analytes from the carriers (the precipitates) should be first examined, and the blank test carried out carefully. Great care should also be taken in terms of the recoveries of the analytes, because the procedures in the coprecipitation are sometimes time-consuming and irre-producible. Some efficiencies of recovery for Zr(IV) coprecipitation along with the determined values of trace elements in seawater are summarized in Table 7, where inductively-coupled plasma (ICP) emission spectrometry was applied for the simultaneous multielement analysis [45]. In this experiment, 10 mg of Zr(IV) was added to 11 of seawater, the precipitation made... 

Other reports deal with individual elements, such as Ni [1, 86, 87] or Fe [11,84]. The efficiency [71—73] of flame methods (AAS) has been compared with flameless techniques (NFAAS) (Table 6). Because of their significance there have been attempts to determine the elements P [38] and S [78] directly with AAS. This, however, requires a device which can measure ultraviolet lines (ca. 180 nm) with sufficient sensitivity. Good results can also be achieved by gas chromatographic separation and successive AAS determination [92] and simultaneous multielement analysis with a Vidicon-detector has been tried [68] because the speed with which the information is gained can be very important in practice. Some work [39, 53] reports on the problem of molecular bands which can appear when working with... 

Hee, S.S.Q., Boyle, J.R. Simultaneous multielement analysis of some environmental and biological samples by inductively coupled plasma atomic emission spectrometry. Anal. Chem. 60, 1033-1042 (1988)... 

The nature of the ICP is such that all elemental information from the sample is contained within it. The only limitation is whether it is possible to observe all the elemental information at the same time or one element at once. This limitation is associated not with the ICP but with the type of spectrometer used to view the emitted radiation. A monochromator allows measurement of one wavelength, corresponding to one element at a time, while a polychromator allows multiwavelength or multielement detection. The former can perform sequential multielement analysis, while the latter carries out simultaneous multielement analysis. The typical wavelength coverage required for a spectrometer is between 167 nm (Al) and 852 nm (Cs). 

X-Ray fluorescence is nondestructive and has significant advantages in simultaneous multielement analysis and ultramicroanalysis using electron beam excitation. It has found widespread industrial applications but as instrumentation is costly and complex in comparison with analytical atomic spectroscopy, the technique is not suitable for routine use in clinical chemistry. It seems unlikely that it can ever be more than a research tool. 

M12. Mitchell, D. G., and Johansson, A., Simultaneous multielement analysis using sequentially excited atomic fluorescence radiation. Specirochim. Acta, Part B 25, 175-182 (1970). 

Simultaneous Multielement Analysis of Biologically Related Samples with RF-ICP... 

An ICAP emission spectrometer in a commercial analytical laboratory can successfully provide accurate, precise multielement data (at major, minor and trace levels) for biological and human-related samples for many of the elements of interest for the related disciplines. The relative freedom from interferences is a very positive attribute. The analytical cost of operation is attractive whenever more than four elements must be analyzed in a sample. The inability of the experimental approach used here to provide analytical data for individual species of the elements is a definite disadvantage when this information is required. The primary requirement for ICAP-simultaneous multielement analysis is exceptionally careful analytical sample preparation methods and laboratory techniques. 

These Initial Investigations of the charge Injection device have Indicated that the device promises to be a successful detector for simultaneous multielement analysis In atomic emission spectrometry. The unique non-destructive readout, coupled with selective knockdown and pseudo-random addressing give the CID system capabilities unparalleled in any other detector available today. The device has been shown to have at least an adequate sensitivity, can be operated in a manner which reduces pixel cross talk, and the dynamic range of the system can be extended to virtually any desired level. 

Dynamic ranges of 3 to 6 orders of magnitude for simultaneous multielement analysis can be attained on performing AAS with a continuum source using a diode array UVV detector LOD 2 pgL 1 for the 328 nm Ag absorption line50. 

Muto H, Abe T, Takizawa Y, Kawabata K, Yama-guchi K and Saitoh K (1994) Simultaneous multielement analysis of daily food samples by inductively coupled plasma mass spectrometry. Sd Total Environ 144 231-239. 

T. Ito, E. Nakagawa, H. Kawaguchi, and A. Mizuike, Semi-Automatic MicroUtre Sample Injection into an Inductively Coupled Plasma for Simultaneous Multielement Analysis. Mikrochim. Acta, I (1982) 423. 

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