EFFECT OF ASCORBIC-ACID ON GRAPHITE-FURNACE ATOMIC-ABSORPTION SIGNALS FOR LEAD

Double-peak atomic absorption signals for lead were observed in the presence of 1% (m/v) (mass/volume) ascorbic acid when the nonpyrolytic coated graphite (NPG) tube was used. The signal with double peaks could be separated into two signals: The position of the first peak was in agreement with the position of the signal in the absence of ascorbic acid using the pyrolytic graphite (PG) tube, and the position of the second peak was in agreement with the position of the signal in the absence of ascorbic acid using the NPG tube. A less porous and smooth surface was found by using scanning electron microscopy on the NPG tube wall after pyrolyzing ascorbic acid. It was considered that pyrolyzing ascorbic acid produced PG-coated sites on the NPG tube that lead to the appearance of the first peak.