Chromatographic study of oil products component composition in sediments

Abstract

Oil products are extremely complex mixtures of different classes compounds containing mostly hydrocarbons.
The main groups of hydrocarbons are aliphatic (as indicative and maximum of oil components
content); naphthenic; aromatic, including polycyclic aromatic hydrocarbons (PAH), known for their harmful
and hazard influence. The main aim of the research was the choosing optimal conditions for simultaneous
determination of different classes hydrocarbons (aliphatic and polycyclic aromatic hydrocarbons). The sediments
analysis scheme consists of: organic solvents extraction; elimination of suspended particles; extracts
cleaning up by distribution of interfering hydrophilic components by the water; preconcentration; extracts
fractionation by column chromatography; final concentration of aliphatic fraction to 1 ml; solvent exchange
of PAH hexane-methylene chloride fraction to 1 ml acetonitrile and analysis by gas and high performance
liquid chromatography (HPLC). Gas chromatographic with mass-spectrometric detection analysis of nalkanes
was carried out by Agilent Technologies 6850/5975C. Detection was performed as mass range 30-
450 a.e.m. scanning. HPLC analysis was carried out by Agilent Technologies 1260 Infinity with fluorescence
detector. Optimal conditions for PAH registration by variation of excitation and emission wavelengths to
detect maximal analytical signal of each compound of interest were chosen. Elution scheme of extracts fractionation
by column chromatography with silica gel Davisil (Grade 635) was proposed and proved experimentally
to separate quantitatively aliphatic and polycyclic aromatic hydrocarbons fractions. Mixes of organic
solvents (acetone-hexane; acetone-hexane-methylene chloride and acetone-hexane-methylene chloride-ioctane)
were used as extragents. Appropriate solvent for effective extraction of hydrocarbons from sediments
to be able prevent semivolatile components evaporation by concentrating was chosen. PAH and aliphatic hydrocarbons recoveries ranged from 80 % and 70 % and over, respectively. The scheme was applied for oil
components determination in sediments from Baikal lake.