Detection of High Molecular Weight Organic Tracers in Vegetation Smoke Samples by High-Temperature Gas Chromatography−Mass Spectrometry

Abstract

High-temperature high-resolution gas chromatography (HTGC) is an established technique for the separation of complex mixtures of high molecular weight (HMW) compounds which do not elute when analyzed on conventional GC columns. The combination of this technique with mass spectrometry (i.e., HTGC−MS) is not so common and application to aerosols is novel. The HTGC and HTGC−MS analyses of smoke samples taken by particle filtration from combustion of different species of plants provided the characterization of various classes of HMW compounds reported to occur for the first time in emissions from biomass burning. Among these components are a series of wax esters (long chain alcohols esterified with long chain fatty acids) with up to 58 carbon numbers, aliphatic hydrocarbons (C15−C40; Cmax = C31; odd predominance), triglycerides, long chain methyl ketones (up to 37 carbons; Cmax = C33; odd predominance), alkanols (up to 40 carbons; Cmax = C32; even predominance), and a series of triterpenyl fatty acid esters (e.g., α- and β-amyryl stearate) which have been characterized as novel natural products. Long chain fatty acids with more than 32 carbon numbers are not present in the smoke samples analyzed. The HMW compounds in smoke samples from the burning of plants from Amazonia indicate the input of directly volatilized natural products in the original plants during their combustion. However, the major organic compounds extracted from smoke consist of a series of lower molecular weight polar components, which are not natural products but the result of the thermal breakdown of cellulose and lignin. In contrast, the HMW natural products may be suitable tracers for specific sources of vegetation combustion because they are emitted as particles without thermal alteration in the smoke and can thus be related directly to the original plant material.