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United States Department of Agriculture

Agricultural Research Service

Title: Continuum Source-Atomic Absorption Spectrometry Using a Two-Dimensional Charge Coupled Device

Authors
item Schuetz, Marcus
item Murphy, James
item Fields, Robert - PAST FCL EMPLOYEE
item Harnly, James

Submitted to: Spectrochimica Acta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 5, 2000
Publication Date: December 30, 2000
Citation: Schuetz, M., Murphy, J.R., Fields, R.E., Harnly, J.M. 2000. Continuum source-atomic absorption spectrometry using a two-dimensional charge coupled device. Spectrochimica Acta.

Interpretive Summary: Solid state array detectors allow multielement detection and inspection of the spectral region around the wavelength of interest. This same approach can be applied to atomic absorption spectrometry when a continuum source is used; the asorption profile appearing as a dip in the intensity. If a 2 dimensional array is combined with an echelle spectrometer, the continuum is seen as parallel bands where each band is a successive wavelength segment on a different dispersion order. With a small, two-dimensional array, a region 1.6 x1.6 mm can be viewed that is suitable for single element determinations. The acquired data allows absorbances to be computed that are corrected for stray light, broad band absorption, structured interferences, and non-uniform distribution of atoms in the atomizer. The computed absorbances have an accuracy that is unattainable with commercial spectrometers. This manuscript describes the operating characteristics of the array detector, the method of computing absorbance, initial results for vertical profiling, and analytical sensitivities and detection limits. This work advances the technology for trace metal analysis and is of interest to instrument manufacturers.

Technical Abstract: A single element continuum source-atomic absorption spectrometer (CS-AAS) has been constructed using a graphite furnace atomizer and a thinned, back-illuminated, two-dimensional, split-frame transfer charge coupled array detector (CCD). Transfer of charges from the integrating arrays to the storage arrays took 0.65 ms, less than 4% of the frame period (16.43 ms). Vertical smearing was observed as a continuum background and can be corrected to preserve the image integrity. The computed absorbances are corrected for stray radiation and non-specific background absorption and can be visually inspected for spectral interferences. The two-dimensional array allows measurement of absorbance with respect to wavelength (4.7 pm resolution) and height (.057 mm resolution) in the furnace. Transmitted intensities were slightly poorer than previously determined with a linear photodiode array due to the extra mirror in the radiation path and/or differences in the quantum efficiencies of the two detectors. The intrinsic masses were similar to those measured previously with CS-AAS. The detection limits were equal to or within a factor of 2 of those determined previously by CS- AAS.

Last Modified: 12/17/2014
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