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United States Department of Agriculture

Agricultural Research Service


item Harnly, James - Jim
item Smith, Clare
item Wichems, Desmond

Submitted to: Journal of Analytical Atomic Spectrometry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/14/1997
Publication Date: N/A

Interpretive Summary: A multielement atomic absorption spectrometer based on a continuum source and an echelle spectrometer was designed and patented at USDA. Successful commercialization of this instrument requires a solid state detector which consists of a series of linear charge coupled arrays buried in single silicon chip (SCD). An SCD detector has been developed for use with a commercially available emission spectrometer. This SCD detector is designed specifically for emission spectrometry and is too expensive for atomic absorption spectrometry. In this study, the emission source was removed and a continuum source and a graphite furnace were mounted in the optical path of the emission spectrometer-SCD detector. For the simultaneous detection of 8 elements, the emission spectrometer-SCD detector provided detection limits that exceeded the best results previously obtained with a continuum source and were generally better than those obtained with commercially available AA instruments. The results of this study unequivocally demonstrate the technical feasibility of this type of the SCD detector for continuum source AA. Commercialization is now an economic issue. Can an SCD detector be developed at a cost which makes continuum source AA economically competitive?

Technical Abstract: A commercially available echelle spectrometer with a segmented charge coupled array detector (SCD) were used with a xenon arc lamp and graphite furnace atomizer for continuum source-atomic absorption spectrometry (CS-AAS). Up to 8 elements were determined simultaneously with a read frequency of 50 Hz for each sub-array. The low read noise of the SCD resulted in the absorbance measurements being limited by the photon shop noise of the continuum source. The high luminosity of the echelle and the high quantum efficiency SCD provided photoelectron levels that ranged from equivalent to 7 times higher than those previously measured by CS-AAS using a linear photo diode array (LPDA) detector. Detection limits were obtained that ranged from equivalent to a factor of 3 better than those previously obtained for CS-AAS and from a factor of 2 worse to a factor of 10 better than those for conventional, line source AAS. Computed intrinsic masses were similar to those previously measured. The high resolution of the echelle allowed detailed inspection of the spectra surrounding the wavelength of the elements determined using contour absorbance plots. A low sensitivity Pd line was identified that was 15 pm from the Se line and was resolved using a theoretical spectral bandpass of 3 pm/pixel.

Last Modified: 8/24/2016
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