Electrochemical determination of elemental sulfur in Brazilian naphtha: method and validation

Abstract

Sulfur compounds in petroleum have caused several problems such as corrosion of equipment, lack of high quality final products, and emission of toxic gases into the environment. Elemental sulfur can increase these problems, since small amounts of it turn mercaptans into potential corrosion agents. This paper describes the applicability of a voltammetric method to quantify elemental sulfur in Brazilian naphtha samples. Elemental sulfur was quantified in synthetic and real samples using square wave voltammetry and a hanging mercury drop electrode. The method was found to have low limits of detection (0.003 mg L -1 ) and quantification (0.009 mg L -1 ) and a good recovery range (94.0-108.6%). This voltammetric method has potential for use in elemental sulfur determination in naphtha samples containing mercaptans and aliphatic and aromatic disulfides.

Use of Hg-Electroplated-Pt Ultramicroelectrode for Determining Elemental Sulphur in Naphtha Samples

“…All reagents were of pure grade and thus were used without any further purification, except for metallic copper powder, which was passed through an activation process [ 6 , 7 ]. Methanol, ethanol, acetone, diethyl ether, 70% (m/m) nitric acid, 98% (m/m) sulphuric acid, 99% (m/m) glacial acetic acid, sodium acetate, potassium nitrate, mercury (I) nitrate, n-heptane, 1-butanethyol, 1-propanethyol, 2-methyl-2-propanethyol, dipropyl disulphide, diphenyl disulphide, elemental sulphur monoclinic, and metallic copper powder (particles <63 μ m and >230 mesh) were purchased from Merck.…”

“…Hydrogen sulphide, elemental sulphur, mercaptans and disulphides account for approximately 1% of the total sulphur content in naphthas. Therefore, developing methods for determining trace amounts of elemental sulphur have been an important challenge in chemical analysis [ 6 ].…”

“…Although elemental sulphur has been studied for many decades [ 11 ], few changes can be observed from the different methodologies developed over time. Different working mercury electrodes, electrolyte solutions, and techniques have been combined to achieve better analytical conditions, as well as faster and more accurate analysis [ 6 , 7 , 12 – 21 ].…”

“…Recently, an electrochemical method was developed in which a small amount of sample was directly analysed by square-wave voltammetry (SWV) using a hanging mercury drop electrode [ 6 , 7 ] in an electrochemical cell containing 10.0 mL of the supporting electrolyte, that is, a buffer solution containing 2% (v/v) glacial acetic acid and 1.4 mol L −1 sodium acetate in methanol. This method showed a linear response in the concentration range studied (0.010 to 0.238 mg L −1 ), low detection limit (0.003 mg L −1 ), and good recovery and precision.…”

Screen-Printed Carbon Electrodes Modified with Cobalt Phthalocyanine for Selective Sulfur Detection in Cosmetic Products

“…Since adverse effects manifest when sulfur limits are exceeded, it is essential to detect and determine the sulfur levels in cosmetic products. Numerous analytical methods such as high performance liquid chromatography (HPLC) [ 4 , 5 ], inductively coupled plasma (ICP) techniques [ 6 – 8 ], polarography [ 9 , 10 ], X-ray fluorescence [ 11 ] and gas chromatography (GC) [ 12 – 14 ] are available for measuring sulfur levels, but not in cosmetic products. Although, these techniques are accurate, fast, and sensitive, they are expensive and offer poor sulfur selectivity and sensitivity due to their complex sample preparation steps.…”