GAS CHROMATOGRAPHIC -MASS SPECTROMETRIC CHARACTERIZATION OF MONOMETHYLALKANES FROM FUEL DIESEL

Abstract

The programmed-temperature linear retention indices of all 196 C 4 –C 30 monomethylalkanes on OV–1 stationary phase were measured with an average repeatibility of ± 0.07 i. u. The mixture of C 9 –C 30 monomethylalkanes was prepared by methylene insertion reaction to C 8 –C 29 n–alkanes mixture. The preliminary identification of monomethylalkanes was performed on the basis of the dependence of homomorphy factors on the number of carbon atoms of individual homologous series of monomethylalkanes. The prediction of retention of isomers with new position of methyl group beginning at higher carbon atoms number, as well as for second, third, fourth etc. member of homologous series allowed the dependence H P =f(C n) for first, second, third etc. members of beginning homologous of monomethylalkane series. The identification was confirmed by mass spectrometry. All gas chromatographic unseparated monomethylalkane isomers with methyl-group near the middle of molecule carbon chain were resoluted by mass spectrometric deconvolution. Obtained regular dependences H P =f(C n) allow precise retention prediction of monomethylalkanes >C 30 . These analytical procedures were used for identification of monomethylalkanes from fuel diesel.