Investigation of the automated determination of As, Sb and Bi by flow-injection hydride generation using in-situ trapping on stable coatings in graphite furnace atomic absorption spectrometry

Abstract

Flow-injection hydride generation and in situ concentration of As, Sb and Bi hydrides in graphite furnace atomic absorption spectrometry can be automated by means of a long-term stable trapping reagent replacing the Pd modifier. In a systematic study, carbide-forming elements (Zr, Nb, Ta, W) and noble metals (Ir, Ir/Mg, Pd/Ir) were investigated as stable adsorbers which require only a single application. Trapping temperature curves indicate high signals for trapping of As at 750-800 degrees C, Sb at 450-8000 degrees C and Bi at 100-500 degrees C on Zr-coated tubes. Ir- and Ir/Mg-coated tubes showed a high response for Sb and Bi at lower temperatures, but based on signal stability and reproducibility (over 400 trapping and atomization cycles tested) the better performance was found with the Zr-coated tubes. The radiotracers Sb-125 and Bi-207 were used to measure the hydride generation (>95% for both elements) and trapping efficiency (91% for Sb and 56% for Bi) on the Zr-coated tube. An adsorptive "carry-over effect" was observed with Sb and Bi but not with As, and trapping temperatures above 450 degrees C with Sb and 350 degrees C with Bi (the "critical temperatures") can lead to errors in absorbance values. On a Zr-coated tube the characteristic mass was about 16 pg for As, 15 pg for Sb and 9 pg for Bi (peak height) and the detection limits (3 sigma) were about 0.015, 0.010 and 0.027 ng, respectively, with a 1 ml sample loop. The method was tested by the determination of the elements in NIST low-alloy steel certified reference materials.

Hydride generation atomic absorption spectrometry with insitu graphite tube trapping for the determination of Se (IV) and Se (VI) in baltic sea water samples

“…In order to improve the situation, a method of automatic introduction of the volatile hydrides into the atomiser should be examined. Nevertheless, it should be emphasised that even the simplest variant of determinations with the manual insertion of the capillary tube results in a relative standard deviation (RSD) in the range of 4.2 % -12.8 % for the concentrations of 2 ng/ml, and 0.1 ng/ml for determinations of the total content of selenium, which is acceptable for this concentration of selenium and comparable with the results reported by other authors [9,21,22].…”

“…In order to enhance the e®ectiveness of the pre-concentration, the walls of the graphite tube are covered with a modi¯er, which is either introduced at the appropriate stage of the thermal cycle or electrothermally deposited [3]. The modi¯ers can be the compounds of palladium [4][5][6][7][8], magnesium [6,9,10], zirconium [11], iridium [8,[11][12][13][14], or permanent modi¯ers like Zr, Ir, W, Nb [5,15,16]. Palladium and other metals are able to bind selenium as intermetallic compounds, which evaporate at temperatures higher than selenium itself [17,18], although this mechanism has been criticised by other authors [19].…”

Comparative efficacy of platinum group metal modifiers in electrothermal atomic absorption spectrometry

“…Trapping of bismuth hydride by PGM modifiers has been investigated [24,29]. Haug and Liao [29] reported that shifting of atomic signals for bismuth to higher temperatures was more pronounced in the presence of Pd modifier as compared to Ir.…”

“…Haug and Liao [29] reported that shifting of atomic signals for bismuth to higher temperatures was more pronounced in the presence of Pd modifier as compared to Ir. Using a fixed atomization temperature (2600 8C) and peak height measurements, the sensitivity for Sensitivity for Cd in extracts was always higher for the permanent modifiers compared to Pd+Mg.…”

Speciation analysis of inorganic form of arsenic in ground water samples by hydride generation atomic absorption spectrometry with insitu trapping in graphite tube

“…The modifiers can be the compounds of palladium [1,[7][8][9][10][11], nickel [11,12], magnesium [11] and such metals as rhodium [13], zirconium [5], iridium [1,9,14], which can also be applied as permanent modifiers [15]. Apart from the solutions of the modifier salt, often a surfactant is also applied.…”