Diode laser atomic absorption spectrometry

Through the availability of tunable diode laser sources the set-up used for atomic absorption (see Section 4.2.2) can be simplified considerably. In this way, several additional advantages can be realized. As through wavelength tuning, measurements in the wings of the absorption profile can also be made, and possible improvements to the linear dynamic range in a number of cases could be expected. 

Through the use of more than one diode and tuning them to several analyte lines, multielement determinations and the use of an internal standard become simple. In AAS work the latter also enables instrumental drift to be overcome and/ or the short-term precision to be improved as well. For the detection, all that is required is pulsing of the primary source and the use of lock-in amplification or a Fourier analyzer. 

Furthermore, tuning of the primary source enables off-peak measurements and background correction to be made directly. 

As discussed earlier, present limitations of diode laser atomic absorption lie in the fact that the lower wavelengths are not yet accessible and that the whole wavelength range cannot be covered continuously as there are wavelength gaps between the wavelength ranges of the diodes presently available. 

In AAS, systematic errors are often due to non-element specific absorption, which necessitates the use of background correction procedures. The absence of nonelement specific absorption can only be expected in the analysis of sample solutions with low matrix concentrations by flame AAS, but in furnace AAS work background correction is required particularly for matrix loaded solutions. The determination of the non-element specific absorption can be performed in several ways. 

An interesting approach to the use of diode laser atomic absorption lies in the use of discharges under reduced pressure as atom reservoirs. In the case of helium low pressure microwave discharges, for instance, metastable levels of elements such as halogens, hydrogen, oxygen or sulfur are excited, which can be 

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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. 

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. 

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. 

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. 

Butcher D. J., Zybin A., Bolshov M. A. and Niemax K. (1999) Specia-tion of methylcyclopentadienyl manganese tricarbonyl by high performance liquid chromatography-diode laser atomic absorption spectrometry, Anal. Chem. 71 5379-5385. 

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