Determination of Thallium, Manganese, and Lead in Food and Agricultural Standard Reference Materials by Electrothermal Atomizer Laser-Excited Atomic Fluorescence and Atomic Absorption Spectrometry with Slurry Sampling

Abstract

Electrothermal atomizer laser-excited atomic fluorescence spectrometry (ETA LEAFS) and electrothermal atomic absorption spectrometry (ETA AAS) have been compared for the determination of three elements in National Institute of Standards and Technology food and agricultural standard reference materials with dissolved and slurried samples. Advantages of slurry sampling include reduced sample preparation and a reduced risk of contamination. ETA LEAFS is an extremely sensitive technique, with detection limits one to four orders of magnitude more sensitive than ETA AAS. Using the front-surface illumination approach, this paper reports the first application of a modern, unmodified graphite tube furnace for the determination of manganese, thallium, and lead in biological materials by ETA LEAFS. Thallium was determined by ETA LEAFS at levels one to two orders of magnitude below the ETA AAS detection limit. The determinations done by ETA LEAFS with the use of either dissolved or slurry sampling agreed well with the certified values, with typical analytical RSDs between 3 and 10%. These precisions were similar to the precisions of the ETA AAS measurements. For ETA AAS, the sizes of the background signals reported in the literature are often about the same order of magnitude as the analytical signal. In this work, the sizes of the background signals for ETA LEAFS were shown to be negligible relative to the fluorescence signals for most samples investigated. The relatively small size for the ETA LEAFS background signals, when compared to ETA AAS background signals, indicates that background correction errors are less likely, and that stringent specifications might be unnecessary for ETA LEAFS background correction instrumentation.