Akira Yonetani

Effect of refractory element carbide coating of a pyrolytically coated graphite furnace on injectable sample volume in the electrothermal atomic absorption spectrometric determination of lead

The effect of treating the surface of a pyrolytically coated graphite furnace with various refractory elements, such as Hf, Nb, W and Zr, on the injectable sample volume was evaluated in order to enhance the sensitivity. Treatment with W made it possible to introduce a 100 µl aliquot of sample solution into the furnace with a high precision (RSD 0.99) between integrated absorbance and injection volume was observed in the range 0–100 µl. Use of a Pd modifier made it possible to enhance the precision (RSD <2%) and the stability of the integrated absorbance (RSD <2.5%) for up to 250 firings. A good linearity was also observed. The calculated detection limit and characteristic mass (sensitivity) were 0.02 µg l–1 and 12 pg, respectively, for a 100 µl injection with the Pd modifier at the optimum ashing temperature of 1400 °C. An interference study was also carried out. The recoveries of 2 µg l–1 Pb added to various water samples, such as snow, rain, river water and tap water were 96–106%.

Study of the Roles of Chemical Modifiers in Determining Boron Using Graphite Furnace Atomic Absorption Spectrometry and Optimization of the Temperature Profile During Atomization

The measurement conditions for determining boron using graphite furnace-atomic absorption spectrometry (GF-AAS) were investigated. Differences in the boron absorbance profiles were found using three different commercially available GF-AAS instruments when the graphite atomizers in them were not tuned. The boron absorbances found with and without adjusting the graphite atomizers suggested that achieving an adequate absorbance for the determination of boron requires a sharp temperature profile that overshoots the target temperature during the atomization process. Chemical modifiers that could improve the boron absorbance without the need for using coating agents were tested. Calcium carbonate improved the boron absorbance but did not suppress variability in the peak height. Improvement of boron absorbance was comparatively less using iron nitrate or copper nitrate than using calcium carbonate, but variability in the peak height was clearly suppressed using iron nitrate or copper nitrate. The limit of detection was 0.0026 mg L(-1) when iron nitrate was used. It appears that iron nitrate is a useful new chemical modifier for the quick and simple determination of boron using GF-AAS.

Single drop surface modified graphite furnace atomic absorption spectrometry for large volume injection: determination of cadmium

The W-treated pyrolytic graphite (PG) furnace made it possible to enhance the precision (RSD < 2%), detection limit (2.5 ng l−1) and sensitivity of Cd by a 100 µl injection with 5 µl of 2000 mg l−1 of Pd modifier for 300 firings. The morphological change of sample deposited during the dry stage was observed in order to understand the high precision of atomic absorption of Cd within a W-treated PG furnace. It was found with the W-treated PG furnace that the sample deposited was constricted into the center area of the sample compartment of the furnace at any volume in the range 10–100 µl and was vaporized smoothly without formation of any bubble. A distribution with higher density of Cd in the center area after the dry stage was observed by the atomic absorption measurement of the small cores collected from the furnace inner wall. The high precision resulted in the distribution of Cd during the dry process of sample solution. The recoveries of 60 ng l−1 Cd added to snow, river and tap water samples were 96.4–105%.