CHARACTERIZATION OF HYPERBOLIC CALIBRATION CURVES FOR CONTINUUM SOURCE ATOMIC ABSORPTION SPECTROMETRY WITH ARRAY DETECTION

Authors: Wichems, Desmond; Fields, Robert; Harnly, James - Jim

Submitted to: Journal of Analytical Atomic Spectrometry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: When a continuum source (CS) and an array detector are used for atomic absorption spectrometry (AAS), calibration curves can be constructed which cover in excess of 6 orders of magnitude of concentration. This exceeds conventional AAS by a factor of 1000. It was found that a hyperbola with proper coefficients and rotated axis could be fit perfectly to the calibration standards. The inherent shape of the hyperbola and the theoretical shape of the calibration curves are a perfect match. The same hyperbola can be fit to every element using appropriate offsets on the X and Y axis. It is shown that the hyperbolic calibration curve can be fit using as few as 2 calibration standards. The relative concentration errors arising from this few standards was not significant compared to other noise sources. Thus, calibration curves covering 6 orders of magnitude of concentration can be constructed for CS-AAS. This research was done as part of a CRADA with the Perkin-Elmer Corporation and is an important development in the commercialization of CS-AAS. The fundamental aspects of this research will be of considerable interest to other researchers and to the analytical instrument community.

Technical Abstract: The suitability of a hyperbolic calibration curve for continuum source-atomic absorption spectrometry (CS-AAS) using graphite furnace atomization and array detection was rigorously tested for Ag (328.1 nm), Cd 9228.8 nm) and Pb (283.3 nm) using a series of 25 calibration standards covering 6 orders of magnitude of concentration. The same hyperbolic shape, with appropriate offsets of the X and Y axis, was suitable for all elements. Despite correction of all computed absorbances for stray light and normalization of concentration by intrinsic mass, each element required a unique set of X and Y axis offsets. The inflection point of the hyperbolic calibration curve was elemental and temperature dependent. These shifts arose from fundamental differences in the shape of the absorbance profile due to the ratio doppler and collisional broadening. As few as 2 calibration standards can be used to construct a calibration curve for CS-AAS which covers 6 orders of magnitude of concentration.