Diode laser atomic spectrometry

In a system for coherent forward scattering, the radiation of a primary source is led through the atom reservoir (a flame or a furnace), across which a magnetic field is applied. When the atom reservoir is placed between crossed polarizers scattered signals for the atomic species occur on a zero-background. When a line source such as a hollow cathode lamp or a laser is used, determinations of the respective elements can be performed. In the case of a continuous source, such as a xenon lamp, and a multichannel spectrometer simultaneous multielement determinations can also be performed. The method is known as coherent forward scattering atomic spectrometry [309, 310]. This approach has become particularly interesting since flexible multichannel diode array spectrometers have became available. 

In addition, for speciation coupling of flow injection analysis and column chromatography with flame AAS and also a direct coupling of HPLC with flame AAS, as is possible with high-pressure nebulization, are most powerful. Here the Cr line in the visible region can be used, which makes the application of diode laser atomic absorption spectrometry possible [325]. This has been shown recently by the example of the determination of methylcyclopentadienyl manganese tricarbonyl. 

Glow discharges have also now been miniaturized. In the discharge in a micro-structured system, described by Eijkel et al. [607], molecular emission is obtained and the system can be used successfully to detect down to 10 14 g/s methane with a linear response over two decades. A barrier-layer discharge for use in diode laser atomic spectrometry has also been described recently (Fig. 122) [608],... 

When using two lasers and applying two-photon spectroscopy, only those atoms that do not have a velocity component in the observation direction will undergo LEI. Then the absorption signals become very narrow (Doppler-free spectroscopy). This enhances the selectivity and the power of detection, however, it also makes isotope detection possible. Uranium isotopic ratios can thus be detected, similarly to with atomic fluorescence [673] or diode laser AAS. Thus for dedicated applications a real alternative to isotope ratio measurements with mass spectrometry is available. 

Niemax K., Zybin A., Schnurer-Patschan C. and Groll H. (1996) Semiconductor diode lasers in atomic spectrometry, Anal Chem 68 351A-356A. 

Groll H., Schnurer-Patschan C., Kuritsyn Yu. and Niemax K. (1994) Wavelength modulation diode laser atomic absorption spectrometry in analytical flames, Spectrochim Acta, Part B 49 1463-1472. 

Speciation of methylcyclopentadienyl manganese tricarbonyl by high performance liquid chromatography-diode laser atomic absorption spectrometry, Anal Chem 71 5379-5385. 

Smith B. W., Quentmeier A., Bolshov M. and Niemax K. (1999) Measurement of uranium isotope ratios in solid samples using laser ablation and diode laser-excited atomic fluorescence spectrometry, Spectrochim Acta, Part B 54 943—958. 

Diode laser sources Already in 1980, lasers had been suggested as excitation sources for atomic absorption spectrometry [11]. Tunable dye lasers can provide virtually any atomic hne between 213 and 900 run with a bandwith corresponding to the natural hne width of an atomic hne and with a comparatively high intensity. However, they have not found widespread acceptance for this apphcation so far due to their cost and complex operation compared to hollow cathode or electrodeless discharge lamps. This situation seems to have changed with the advent of inexpensive, mass produced diode lasers (DL) [12, 13]. 

Tunable lasers (preferentially dye lasers and diode lasers) are used as primary sources for atomic absorption spectroscopy with various atomizers such as flames, furnaces, or plasmas LAAS laser atomic absorption spectrometry CRS cavity ring-down spectroscopy... 

Butcher DJ, Zybin A, Bolshov MA, and Niemax K (2001) Diode laser atomic absorption spectrometry as a detector for metal speciation. Review of Analytical Chemistry 2 79-100. 

Koch J, Miclea M, and Niemax K (1999) Analysis of chlorine in polymers by laser sampling and diode laser atomic absorption spectrometry. Spectrochimica Acta B 54 1723-1735. 

Kogh J. and Niemax K (1998) Characterization of an element selective GC-detector based on diode laser atomic absorption spectrometry, Spectrodum Acta, Part B 53 71—79. 

Atomic Absorption Spectrometry with Diode Lasers [6], [8]... 

Diode laser atomic absorption spectrometry (DLAAS) ... 

A. Zybin, J. Koch, H. D. Wizeman, J. Franzke and K. Niemax, Diode laser atomic absorption spectrometry, Spectrochim. Acta, Part B, 2005,60,1-11. 

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