Abstract
A method for chlorine determination in crude oil samples, through the formation of MgCl molecule, by high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) was developed and is described in this paper. The use of this molecule for chlorine determination in crude oil has not been reported up to now. Measures were carried out at the wavelength 377.010 nm and the samples were submitted to a simple treatment as emulsion, whose composition was optimized applying a simplex-centroid experimental design. Magnesium was used as molecule forming agent at the concentration of 10 g L-1, at least 500 times higher than the concentration of chlorine. This excess is required to ensure the molecule formation of all content of Cl present in the sample. Chemical modifier Pd was used and improved greatly the signal intensities. Optimized pyrolysis and vaporization temperatures, applied for determination, were 800 and 2300 °C, respectively. Accuracy was evaluated through analysis of certified reference materials, NIST 1848 and NIST 1634c, and addition and recovery tests with recoveries between 92 and 117%. Limits of detection and quantification were 3.0 and 9.0 µg g-1, respectively. The method was applied to eight crude oil samples.
Highlights
Crude oil is a natural complex mixture of gaseous and liquid compounds found in reservoirs beneath the surface of the earth associated with sedimentary rocks, composed mostly of aliphatic and aromatic hydrocarbons and containing organic compounds of nitrogen, oxygen and sulfur
The aim of this paper is to describe a method development for chlorine determination, using MgCl molecule, in crude oil samples by high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS)
Determination of chlorine using MgCl molecule in crude oil samples by HR-CS MAS is proposed in this paper
Summary
Crude oil is a natural complex mixture of gaseous and liquid compounds found in reservoirs beneath the surface of the earth associated with sedimentary rocks, composed mostly of aliphatic and aromatic hydrocarbons and containing organic compounds of nitrogen, oxygen and sulfur. Chlorine is present in crude oil as inorganic metallic salts, whose content is related to the reservoirs, formation waters and other waters used in extraction processes. Organic bonded chlorides from vegetal and animal sources or formed during crude oil processing steps can be present. Found in trace amounts chlorine is very deleterious since during the processing of crude oil it generates hydrochloric acid which is strongly. Chlorine determination in crude oil is not an easy task due to the complexity of the sample and the possibility of analyte lost during the treatment procedures prior the analysis. The procedure of ASTM D4929 describes the quantification of organic chlorides while EPA 9075 defines the total concentration of chlorine in petroleum products but has been applied to crude oil.[3]
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