GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY USING A LINEAR PHOTODIODE-ARRAY AND A CONTINUUM SOURCE

A graphite furnace atomic absorption spectrometer is described based on a continuum source and a linear photodiode array detector (LPDA). Wavelength integrated absorbance is computed which asymptotically approaches a maximum as more pixels are used to cover the absorption profile. The read noise of the LPDA was 3800 electrons. Absorbance noise computed from the propagation of errors and LPDA read noise accurately predicts the experimental results. Absorbance noise decreases as the entrance slit is increased and increases as the number of pixels in the calculation is increased. The best detection limits were found with an entrance slit-width of 500 mum and 16-32 pixels. The detection limits for Cd, Cu and Ni were comparable to line source atomic absorption spectrometry. Gated detection was necessary to eliminate source flicker when large numbers of pixels were used and in the presence of background absorbance.