DETERMINATION OF SULFUR-CONTAINING SUBSTANCES IN MOTOR FUELS BY THE VOLTAMMETRIC METHOD WITH SQUARE WAVE POTENTIAL SCANNING USING SCREEN PRINTED ELECTRODES MODIFIED WITH MERCURY FILM

A method of highly sensitive voltammetric determination of sulfur-containing compounds in motor fuels has been developed. Square-wave voltammetry using mercury-modified screen printed electrodes is used. It is shown that for the separate determination of disulfides, their separation from sulfides and mercaptans on a copper column should be used. The methods of modification of the screen printed electrode with a mercury film and the manufacture of a copper column are given. Using cyclic voltammetry, the electrochemical reversibility of sulfur and disulfide reduction and the quasi-reversibility of mercaptan reduction are shown. Examples of the determination of elemental sulfur, disulfides and mercaptans in gasoline with different octane numbers and diesel fuel sold at gas stations in Samarkand (Uzbekistan) are given. There is a connection between a decrease in the content of sulfur-containing compounds and an increase in the octane number of gasoline. The analysis showed the compliance of the analyzed samples with the Euro 4 and Euro 5 standards used in the European Union and the USA. The main advantage of the proposed method, in addition to high sensitivity and accuracy of determination, is its greater environmental friendliness compared with the use of polarographic determination with a mercury droplet electrode for these purposes.