Simultaneous liquid–liquid extraction of dibenzyl disulfide, 2,6‐di‐tert‐butyl‐p‐cresol, and 1,2,3‐benzotriazole from power transformer oil prior to GC and HPLC determination

Abstract

2,6-Di-tert-butyl-p-cresol (DBPC), dibenzyl disulfide (DBDS), and 1,2,3-benzotriazole (BTA) are additives that may be found concomitantly in the oil matrix of power transformer. DBPC and DBDS act as antioxidants while, BTA is a corrosion inhibitor that protects copper conductors inside the transformer unit from corrosion. A powerful analytical method is, therefore, required to determine these additives at trace levels in the transformer oil. This work describes a unique single liquid-liquid extraction pretreatment step prior to the determination of the components by gas chromatography (GC) and high-performance liquid chromatography (HPLC) techniques. The optimum volume ratio used in the pretreatment step was determined as 5:2:5 for mineral oil/n-hexane/acetonitrile, respectively. Relatively, the method is simple and quick with a minimal use of solvents. Analytical results indicate that the method is relatively sensitive, accurate, and precise for each of the three components in fresh and used mineral oil. The calibration curves for the three components demonstrate a significant increase in sensitivities. Detection limits found were, 100 mg L(-1) (0.01% w/v), 0.80 mg L(-1) , and 2.04 mg L(-1) for DBPC, DBDS, and BTA, respectively. The Student's t values determined at 95% confidence level indicate that there is no significant difference between the experimental means obtained by this method and the standard method for each component.

The minimum concentration of 1,2,3-benzotriazol to suppress sulfur corrosion of copper windings by DBDS in mineral transformer oils

“…Each of the samples in each of the four groups was incubated for 72 hours at (i) room temperature (ii) 150 o C and (iii) 150 o C in the presence of copper strips. At the end of the incubation period all samples were tested for their DBDS concentration using GC-ECD after the liquid-liquid extraction pretreatment step mentioned earlier [16]. Figures 2(a-f) show the DBDS depletion profile in presence of various BTA concentrations (0 -10mgL -1 BTA).…”

“…Flat-bottomed vials with 20 ml headspace and crimp-tops, were filled with all the solutions and incubated for 72 h, at room temperature, at 150 °C, and at 150 °C with a copper plate immersed, according to the IEC 62535 standard method except all solutions inside vials were purged with argon to minimize their contact with air and reduce oxidative depletion in BTA signal. After the incubation period, the concentrations of BTA and DBDS were determined using the liquid-liquid extraction procedure of Jaber et al [16].…”

“…Mehanna et al [17] reported a high rate of thermal degradation of BTA using artificial aging as per ASTM D2440 [18]. This paper reports quantitative determinations of these concentrations using the standard 62535 IEC method after modification to include purging the solutions with argon during the incubation period, followed by the analytical procedure described by Jaber et al [16].…”

Simultaneous Determination of Passivator and Antioxidant Additives in Insulating Mineral Oils by High-Performance Liquid Chromatography

“…Although Jaber et al [12] recently proposed a liquidliquid extraction method for the simultaneous extraction of BTA, DBPC, and DBDS (dibenzyldisulfide), three different analytical methods, namely gas chromatography-flame ionization detection (GC-FID), gas chromatography-electron capture detection (GC-ECD) and HPLC, were required for the determination of the three species.…”

Preparation a new sorbent based on polymeric ionic liquid for stir cake sorptive extraction of organic compounds and inorganic anions

“…37 Typical sample pretreatment includes solvent-based and sorbent-based approach. 38 Solvent-based extraction mainly includes Soxhlet extraction [1], liquid-liquid 39 extraction (LLE) [2] and liquid-phase microextraction (LPME) [3]. Solvent should be 40 used in these extraction approach, and the toxic solvent will do harm to operators and Several excellent papers have reviewed the advances of sorbent materials [17][18][19].…”