Effect of Ascorbic Acid on the Desorption of Gold in Graphite Furnace Atomic Absorption Spectrometry

Abstract

In the graphite furnace atomic absorption spectrometry of gold, signals with a single peak were observed with a pyrolytic graphite (PG) furnace, while signals with a shoulder on the tailing edge were observed with a nonpyrolytic graphite (NPG) furnace. A thermal shift of the atomic absorption signals for gold occurs in response to changes in the concentration of ascorbic acid without any loss for each furnace. When the pre-pyrolysis of a 5% (m/V) ascorbic acid solution was carried out at 1270 K, although the background signal due to the release of amorphous carbon was not observed, a thermal shift of the gold signal was confirmed. At a pre-pyrolysis temperature over 1460 K, the peak absorbance was reduced by increasing the pre-pyrolysis temperature, while absorbance at the position of the signal for gold only was increased. The values of the Arrhenius activation energy for the desorption of gold were obtained to be 60 ± 2 kcal mol−1 for gold only, 93 ± 3 kcal mol−1 for gold with 5% (m/V) ascorbic acid and 99 ± 2 kcal mol−1 after a pre-pyrolysis of ascorbic acid at 1270 K.

Effect of the Chemical Species of Arsenic on Sensitivity in Graphite Furnace Atomic Absorption Spectrometry

“…[25][26][27][28][29][30] In this study we investigated the atomization process of As using the enthalpy change (ΔH) at the atomization stage. Arsenic usually forms oxides at the pyrolysis stage in GFAAS and is atomized through the following processes:…”

Atomization Mechanisms of Gold from Thermally Decomposed and Crudely Roughened Pyrolytically Coated Graphite Furnaces Using Electrothermal Atomization

“…[3][4][5][6] Fonseca and co-workers 7 reported that vaporization of gold and silver appears to occur from varying sizes of microdroplets or from adatoms, depending on the analytical conditions, such as dry and thermal pretreatment conditions, chemisorbed oxygen on the graphite surface and mechanically created active sites on the graphite surface. In the case of silver, although a tendency of the activation energy (E a ) for atomization to increase as the concentration increases was observed with a fractional order desorption, a constant E a was observed below 0.06 ng of silver, which is in agreement with the morphology of dispersed atoms with a first order desorption.…”

Effect of the Surface Treatment of a Graphite Furnace with a Refractory Element (Hafnium, Titanium, Tungsten and Zirconium) by a One-Drop Coating Method on the Atomization Mechanism of Indium in Electrothermal Atomic Absorption Spectrometry

“…29 Arrhenius plots with a single slope were obtained for the Hf-, Ti-and Zr-treated PG furnaces. With the W-treated PG furnace, the first peak was observed as a small shoulder which was too small to deserve a kinetic analysis.…”