IDENTIFICATION OF BRANCHED ALKANES IN LIPIDS OF LEPTINOTARSA-DECEMLINEATA SAY AND TRIBOLIUM DESTRUCTOR BY GC-MS - A COMPARISON OF MAIN-BEAMAND LINK-SCANNED SPECTRA

Branched hydrocarbons were identified in the lipids of Leptinotarsa de cemlineata Say and Tribolium destructor by gas chromatography, ordinar y electron impact mass spectrometry, and linked, scanned, daughter-ion monitoring. This methodology allowed us to revise our earlier results based only on CC-MS data confirming the existence of only monomethyl- , dimethyl-, and trimethylalkanes in the hydrocarbons of L. decemlinea ta Say. The hydrocarbons from Tribolium destructor consist of n-alkane s, 3-methylalkanes, internally branched monomethylalkanes and dimethyl alkanes. Daughter-ion monitoring can be particularly important for dis tinguishing between incidentally overlapped GC peaks of hydrocarbons f rom different series. A trace, for example, of dimethylalkane coeluati ng with n-alkane was easily identified in GC peak of hydrocarbon mixtu re of T. destructor. Link scans confirmed also molecular weights for t he compounds without molecular ions in the mass spectra. Structural as signment of the compounds were verified by comparison of the experimen tal and calculated values of the GC retention Kovats indexes (KI).