Direct determination of arsenic and antimony in naphtha by electrothermal atomic absorption spectrometry with microemulsion sample introduction and iridium permanent modifier

Abstract

This paper reports the determination of arsenic and antimony in naphtha by employing electrothermal atomic absorption spectrometry (ETAAS) as the analytical technique. In order to promote the direct determination of the analytes in the very volatile naphtha, the formation of a microemulsion with different surfactants (Triton X-100 and Brij-35) and different chemical modification strategies were tested. The results indicated that Triton X-100 is the best emulsification agent for naphtha in both As and Sb determination when it is employed at a concentration of 1% w/v in the microemulsion. Under these conditions, the microemulsion was stabile for at least 2 h. By using Brij-35 it was possible to achieve good stability only in the first 15 min. Among all chemical modification approaches investigated (Ir permanent modifier, W-Ir permanent modifier, and Pd modifier), the Ir permanent modifier provided better sensitivity for both analytes and allowed a higher pyrolysis temperature, which decreased the background signals at lower levels. Under the best conditions established in this work, an RSD of 4.6% (20 microg L(-1)) and a detection limit of 2.7 microg L(-1) were observed for arsenic. For antimony, an RSD of 4.0% (20 microg L(-1)) and a detection limit of 2.5 microg L(-1) were obtained. The accuracy of the procedure was assessed by analyzing spiked samples of naphtha from different origins.

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

“…For the analysis of a spiked SRM sample, only a Ru permanent modifier was used. Very similar data were obtained by Cassella et al [41], who compared Ir and WC+Ir permanent modifiers with a regular Pd(NO 3 ) 2 modifier for the determination of antimony in a naphtha emulsion. As application of the permanent Ir modifier enhanced the graphite tube lifetime twofold compared to that when a regular Pd modifier was used (150 cycles), the former modifier was finally chosen.…”

“…It appears that there are some specific effects in the As-Rh-Na 2 SO 4 system leading to [ 41] suppression of peak area for arsenic in the presence of as few as 10 ng of sulfate ion [32]. In the presence of sodium sulfate and platinum modifier, a slight permanent decrease in the arsenic signal was noted in the region 600-1400 8C.…”

“…However, in other experiments [10], peak tailing for arsenic increased in the order PdbIrbRubPtbRh. Permanent modifiers based on rather large masses of iridium were used for the determination of arsenic in a variety of samples [21,30,[35][36][37]41,42].…”

Analytical Methodology for the Determination of Trace Metals in Biodiesel

“…As can be seen in Figure 2, there is a significant difference between the analyzed standards. The sensitivities of the analytical curves for pure biodiesel (samples S 1 to S 7 ) are consistently lower for the aqueous standard, confirming the reports of some studies in the literature that the sensitivities of emulsified standards differ from those of aqueous standards (Cassella et al, 2004;Reyes  Campos, 2005;Saint´Pierre et al, 2002, 2003. It was also found that the analytical curves of the biodiesel samples did not exhibit the same sensitivity, although they were similar.…”

Direct determination of arsenic in petroleum derivatives by graphite furnace atomic absorption spectrometry: A comparison between filter and platform atomizers

“…These methods were described in several papers for the direct determination of trace elements in petroleum derivatives [5,[11][12][13]. Procedures to obtain one-phase microemulsions or conventional emulsions were also proposed for the determination of As [7,14,15].…”