Differentiation between phenol- and amino-substances in voltammetry determination of synthetic antioxidants in oils

Abstract

Abstract:The paper describes a method of voltammetric determination of antioxidants in lubricating oils developed with the use of Linear Sweep Voltammetry (LSV) and Fast Scan Differential Pulse Voltammetry (FSDPV). Experimental conditions have been found for simultaneous determination of phenol-based antioxidants and amino-antioxidants: the phenols can be electrochemically oxidized using the polarisation of gold disc electrode (AuDE) in the potential range of 0-1400 mV in 0.2 M H 2 SO 4 in the presence of ethanol and acetonitrile at the ratio of 3:1. Secondary aromatic amines can be determined directly in this supporting electrolyte; the presence of phenolic antioxidants does not interfere with this analysis. On the other hand, secondary aromatic amines interfere with the determination of phenolic substances; therefore, the amines present have to be eliminated in a suitable way. A procedure for masking the aromatic amines using their reaction with nitrous acid has been suggested and optimised. The nitrosamines thus formed can be used for sensitive and selective determination of amino-antioxidants by means of cathodic reduction on the hanging mercury drop electrode (HMDE) using Fast Scan Differential Pulse Voltammetry. The method was applied in analysis of real samples of lubricating oils. © Versita Sp. z o.o.

Simultaneous determination of TBHQ and BHA on a MWNT-Brij® 35 modified electrode in micellar media

“…The main advantages of electroanalysis such as high sensitivity and selectivity, rapid response, simplicity and cost-efficiency as well as possibility of miniaturization provide a good alternative to chromatography and spectrophotometry for a routine procedure. 9 A number of bare platinum, [10][11][12][13] gold, [14][15][16][17] and carbon-based electrodes 10,[18][19][20][21] have been used for TBHQ, BHA and related synthetic phenol determination in batch and ow modes. 22,23 Nevertheless, the sensitivity of response is not sufficient in some cases.…”

Electrochemical Behavior of Butylated Hydroxyanisole and Butylated Hydroxytoluene in Acetic Acid Solutions and their Voltammetric Determination in Pharmaceutical Preparations

“…Voltammetric techniques are based on the anodic oxidation of synthetic antioxidants. Due to the limited solubility in water and the presence of a hydrophobic matrix, their electrochemical properties were investigated mainly in solutions of water with methanol [22][23][24][25] or ethanol [26][27][28], and in mixtures of organic solvents as ethanol-acetonitrile [29], benzene-ethanol [30,31]. These solvents are mostly toxic to humans and the environment.…”

“…These solvents are mostly toxic to humans and the environment. The material of the working electrode was usually glassy carbon [22,24], carbon fiber [31], platinum [24,30], gold [29] and diamond boron doped [27]. Oxidation of phenolic compounds especially in water solutions is often accompanied by the phenomenon of blocking the surface of the electrode by polymeric products formed during this process [32].…”

Voltammetric Determination of Dinonyl Diphenylamine and Butylated Hydroxytoluene in Mineral and Synthetic Oil

“…Chýlková et al (2010) simultaneously determined butylated hydroxytoluene and N-phenyl-1-naphthylamine in lubricating oil with a supporting electrolyte of 0.2 mol L −1 H 2 SO 4 in 3:1 ethanol and acetonitrile by linear-sweep voltammetry and fast-scan differential pulse voltammetry. The amines were directly determined in the supporting electrolyte.…”