Zeeman AAS

The Zeeman technique, though difficult to establish, has an intrinsic sensitivity perhaps five-times greater than that of the graphite furnace technique (e.g., 1 pg/1 detection limit for lead). 

The stabilised temperature platform furnace eliminates chemical interferences to such an extent that in most cases personnel- and cost-intensive sample preparation steps, such as solvent extractions, as well as the time-consuming method of additions, are no longer required. 

Neutral particles are heated indirectly hy collisions with the charged particles upon which the field acts. Macroscopically, the process is equivalent to heating a conductor by a radiofrequency field, the resistance to eddy current flow producing joule heating. 

The field does not penetrate the conductor uniformly and therefore the largest current flow is at the periphery of the plasma. This is the so-called skin effect and, coupled with suitable gas-flow geometry, it produces an annular or doughnut-shaped plasma. Electrically, the coil and plasma form a transformer, with the plasma acting as a one-turn coil of finite resistance. 

If mass spectrometric determination of the analyte is to be incorporated, then the source must also be an efficient producer of ions. 

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KuRFiiRST U, Grobecker KH, Stoeppler M (1984) Homogeneity studies in biological reference and control materials with solid sampling and direct Zeeman-AAS. In Schramel P, Bratter P, eds. Trace Element Analytical Chemistry in Medicine and Biology, Vol. 3, pp 591-601. de Gruyter, Berlin. 

Rossbach M, Ostapczuk P, Emons H (1998) Microhomogeneity of candidate reference materials Comparison of solid sampling Zeeman-AAS with INAA. Fresenius J Anal Chem 360 380-383. Rossbach M, Stoeppler M (1987) Use of CRMs as mutual calibration materials and control of synthetic multielement standards as used in INAA. J Radioanal Nud Chem Artides 113 217-223. Sargent M (1995) Development and application of a protocol for quality assurance of trace analysis. Anal Proc 32 71-76. 

The influence of matrix concomitants often cannot be recognised or quantified. Progress in background correction techniques (e.g. direct Zeeman-AAS [218]), furnace techniques, microweighing, and electronic signal processing have gradually made possible the elimination... 

Chromium Chromium Immobilised diphenylcarbazone Cr(III) converted to Tris (1,1,1, trifluoro 2,4 pentanediono) chromium(III), extracted with hexane Zeeman AAS Isotope dilution GC-MS [178] [181,183, 867]... 

Pesch H-J, Bloss S, Schubert J, et al. 1992. The mercury cadmium and lead content of cigarette tobacco Comparative analytical-statistical studies in 1987 and 1991 employing Zeeman-AAS. Fresenius J Anal Chem 343(1) 152-153. 

Zeeman AAS makes use of the splitting of the atomic spectral lines into several components under the influence of a magnetic field. When a magnetic field B (up to 10 kG) is applied, the shift in wavenumber (A Tm) of the so-called cr-components with respect to the original wavelength, where the 71-components may remain, is given by ... 

The detection limits in Zeeman AAS could be expected to be lower than in the case of the background correction with a D2 lamp. Indeed, here the system uses only one source. Accordingly, it can be operated at high intensity, through which detector noise limitations are avoided. This advantage will certainly be most pronounced when one component is measured in an alternating field. 

Another consequence of the use of one primary source will be the better stability of the system. The analytical sensitivity in Zeeman AAS, however, will be inferior to that of conventional AAS. This disadvantage is lowest for a field which can be varied from case to case. 

Coherent forward scattering (CFS) atomic spectrometry is a multielement method. The instrumentation required is simple and consists of the same components as a Zeeman AAS system. As the spectra contain only some resonance lines, a spectrometer with just a low spectral resolution is required. The detection limits depend considerably on the primary source and on the atom reservoir used. When using a xenon lamp as the primary source, multielement determinations can be performed but the power of detection will be low as the spectral radiances are low as compared with those of a hollow cathode lamp. By using high-intensity laser sources the intensities of the signals and accordingly the power of detection can be considerably improved. Indeed, both Ip(k) and Iy(k) are proportional to Io(k). When furnaces are used as the atomizers typical detection limits in the case of a xenon arc are Cd 4, Pb 0.9, T11.5, Fe 2.5 and Zn 50 ng [309]. They are considerably higher than in furnace AAS. 

Pearson. K.H., Schermaier, A.J. and Tytko, S.A. (1983). Evaluation of trace metal vacu-tainer tubes by Zeeman AAS. Clin. Chem., 29,1286 (abstract). 

To compensate for the above effects background correction systems are introduced such as the use of Zeeman effect. Zeeman AAS uses splitting of atomic spectral lines... 

The most significant advantage of inverse Zeeman AAS is that the background is always measured directly at the same wavelength as the atomic absorption of the analyte. This permits accurate correction even when the background is highly structured, but not when non-absorbed lines are present. 

In inverse Zeeman AAS there are some practical constraints on the atomizer due to the need to have the magnet pole-pieces as close together as possible in order to keep the field strength (and the power supply required) as small as can be achieved. Hence, in the case of the flame atomizers, water cooling is necessary to prevent overheating of the magnet pole-pieces. 

Figure 82 Schematic configuration and operation of a DC Zeeman AAS instrument in which the magnet is positioned around the sample. (Adapted from H. Koizumi and K. Yasuda, Spectrochim. Acta, 1976, 31B, 237)...

The sensitivity obtained by transverse AC Zeeman AAS for the elements with the normal Zeeman pattern is good and often nearly the same as for the conventional AAS. In addition, for many elements with the anomalous Zeeman effect such as Ni, Mn, Sb, Tl, and Ag,... 

Figure 86 Calibration graphs for copper (X = 324.8 nm) obtained by transverse AC Zeeman AAS. A magnet off B magnet on A-B ZAAS signal (difference between A and B). (Adapted from F. J. Fernandez, W. Bolder, M. M. Beaty and W. B.

Zeeman-AAS 40-60 suitable for routine, direct measurements in many solid sample types without pretreatment... 

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