Continuum source-atomic absorption spectrometry using a two-dimensional charge coupled device

Abstract

A single element continuum source-atomic absorption spectrometer (CS-AAS) using a two-dimensional charge coupled array detector (2D-CCD) was assembled for use with graphite furnace atomization. The two-dimensional CCD was a split-frame transfer array, was thinned and back-illuminated for high quantum efficiency at approximately 200 nm, and was capable of an 80-Hz frame rate with a read noise of <15 electrons. The transfer of charges from the integrating arrays to the storage arrays took 0.65 ms, less than 4% of the frame period (16.42 ms). The transfer of charges to the storage array was perpendicular to the wavelength axis, eliminating source flicker noise, and was implemented without masking, producing vertical smearing. The smearing was manifested as a continuum background and was corrected using pixels between orders. The two-dimensional array, in conjunction with the high-resolution echelle spectrometer, allowed measurement of absorbance with respect to wavelength and height in the furnace. Computed absorbances were corrected for stray radiation and non-specific background absorption. Detection limits were equal to those for line source AAS, with the exception of As (193.7 nm) and Se (196.0 nm).