Scope and limitations of flash pyrolysis-gas chromatography-mass spectrometry as revealed by the thermal behaviour of high-molecular-weight lipids derived from the green microalga Botryococcus braunii

Abstract

Curie point pyrolysis—gas chromatography/mass spectrometry studies of four types of high-molecular-weight (HMW) lipids isolated from the green microalga Botryococcus braunii race A were performed to determine the thermal behaviour of these lipids and to propose mechanisms of pyrolysis for these types of compounds. Although two types of lipids induced detectable pyrolysis products upon heating of the ferromagnetic wires at Curie temperatures of 610 and 770°C, transfer problems from the pyrolysis unit to the GC column were observed. Therefore, further analysis of the pyrolysis residues is suggested. Furthermore, two types of lipids presenting long alkyl chains (up to C64) did not pyrolyse under the experimental conditions but were thermally extracted from the wire at any of the tested temperatures. Some of these HMW lipids could, however, be analysed by high-temperature gas chromatography (temperatures up to 375°C). Mechanisms of pyrolysis, partly based on previous studies, were proposed for the two types of ether lipids. These mechanisms allowed the structural reconstruction of the main biopolymer that composes the cell outer walls of the microalga B. braunii race L. This biomacromolecule was found to be comprised of C40 isoprenoid (lycopene) units, ether linked at the C(14) and C(15) positions.