Arsenic determination in naphtha by electrothermal atomic absorption spectrometry after preconcentration using multiple injections

Abstract

Naphtha is a petroleum fraction containing C4-C15 hydrocarbon compounds and is used as feedstock for petrochemical processes which are affected profoundly by trace amounts of arsenic. A simple method for arsenic determination in naphtha using electrothermal atomic absorption spectrometry with polarized Zeemaneffect background correction was developed. Multiple injections were used for direct preconcentration in the graphite tube, eliminating sample pretreatment. Doehlert experimental designs were used to find the best settings for the furnace program parameters. Modifier concentration, number of multiple injections and sample volume were also optimized with the same multivariate approach. With three 45 mL sample injections, ashing temperature 1200 uC, atomization temperature 2700 uC and ashing time 60 s, a detection limit of 0.5 mg L 21 and a characteristic mass of 61 pg were achieved, using 3000 mg L 21 Pd(NO 3 ) 2 as the chemical modifier. The relative signal standard deviation was found to be 9.0% at the 2.3 mg.L 21 level. Results from several naphtha test samples showed arsenic levels typically below 3.0 mg L 21 . The high degree of automation of the proposed method minimized technician sample handling allowing its application for routine analysis. This procedure has been used for arsenic determination in naphtha feeds processed in the Braskem Petrochemical (Salvador, Bahia, Brazil).

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

“…Several works have been published combining this approach with flame atomic absorption spectrometry [2,3,4,5,6,7,8]. On the other hand, a limited number of papers can be found describing the use of this procedure in electrothermal atomic absorption measurements [9,10,11,12,13] and other spectroscopy techniques [14,15,16,17].…”

“…Rebouças et al [13] carried out arsenic determination in naphtha samples by direct injection of the sample into the graphite furnace. In this work, the authors employed a multiple injection approach in order to improve the sensitivity of the method.…”

Analyse de métaux traces dans les produits pétroliers, état de l'art

“…En GFAAS en revanche, ces produits sont traités aisément puisque la fraction volatile est lentement éliminée par un programme de montée en température du four permettant l'élimination des composés organiques avant atomisation des éléments d'intérêt. L'avantage de cette méthode procédant par palier est même exploitée par Reboucas et al (2003) qui procède par trois injections successives de 45 µl de naphtas suivies de trois montées en température jusqu'à 180°C permettant d'éliminer les composés les plus volatiles (séchage) tout en concentrant dans le tube graphite les éléments d'intérêt avant atomisation. Cette technique permet de doser l'arsenic entre 0,5 µg/l et 120 µg/l avec 135 µl de produit consommé.…”

“…Cette technique permet de doser l'arsenic entre 0,5 µg/l et 120 µg/l avec 135 µl de produit consommé. Le dosage effectué par Reboucas et al (2003) sur onze produits pétroliers issus de l'Afrique et de l'Amérique du Sud démontre que le gain obtenu entre 5 µg/l et 0,5 µg/l permet de doser efficacement les onze produits contenant tous entre 0,6 et 2,9 µg/l.…”

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

“…It is the main intermediate used by the petrochemical industry for a wide range of chemical products such as benzene, toluene, xylene, ethylene, propylene, etc. [2]. Petroleum condensate is a fraction of hundreds of hydrocarbons, with a distillation range usually from 30 to 330°C, which can substitute naphtha in the petrochemical industry [3].…”