Journal of Chromatography A, 1243 (2012) 69–80 Contents lists available at SciVerse ScienceDirect Journal of Chromatography A jou rn al h om epage: www.elsevier.com/locat e/chroma High temperature gas chromatography–time-of-flight-mass spectrometry (HTGC–ToF-MS) for high-boiling compounds P.A. Sutton ∗ , S.J. Rowland Biogeochemistry Research Centre, School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus, Plymouth PL4 8AA, United Kingdom a r t i c l e i n f o Article history: Received 3 March 2012 Received in revised form 10 April 2012 Accepted 15 April 2012 Available online 24 April 2012 Keywords: HTGC–ToF-MS Triglycerides HMW n-acids and wax esters GDGTs Porphyrins a b s t r a c t High temperature gas chromatography (HTGC) is a routine technique for the analysis of high boiling com- pounds which are eluted from the column with oven cycling up to >400 ◦ C. In contrast, the coupling of HTGC with mass spectrometry (HTGC–MS) has received relatively little attention. This may be due to the availability of GC columns, mass spectrometers and accessories that are able to withstand constant high temperature cycling. We have assembled a HTGC–time of flight-MS (HTGC–ToF-MS) system from readily available products that is capable of rapid (<25 min) analysis of ∼C 10–100 hydrocarbon boiling equivalents and full mass spectral data recording up to m/z 1850. Here we report initial results from the analysis of diverse substrates including:long-chain (>C 60 ) n-alkanes, n-acid methyl esters up to C 64 , triacylglycerides (TAGs) with molecular and fragment ions in a single analysis, intact wax esters from C 40–64 , C 80 glycerol alkyl glycerol tetraethers (GDGTs), and C 33–44 metallated porphyrins. Mass spectrometry at 430 ◦ C was achievable on a routine basis without significant thermal degradation of analytes. The method is appli- cable to analysis of a wide range of industrial, environmental, biological, geochemical and other samples where high molecular weight analytes are of interest. © 2012 Elsevier B.V. All rights reserved. 1. Introduction High temperature gas chromatography (HTGC), where the oven is cycled up to 380/430–450 ◦ C and analytes measured using flame ionisation detection (FID) is now an established technique. FID is useful for HTGC analysis as it offers low discrimination and linear response over several orders of magnitude. HTGC allows for the resolution of mixture constituents within a wide molecular weight range (∼100 to >1400 Da [1], equivalent to n-alkanes from C 7 to >C 100 ) within a single analysis and has recently been adopted for GC × GC [2,3]. Within this volatility range, suitably derivatised polar compounds are also amenable to anal- ysis using HTGC [4]. Cool-on-column is the preferred injection technique, especially for ‘waxy’ samples that are not fully solu- bilised at room temperature [5] which may not be transferred to the column quantitatively using other injection techniques, such as split/splitless or programmable temperature vapouri- sation [6]. System integrity is maintained through the use of graphite ferrules at column connections. Nowadays, manufac- tured steel coated silica capillary columns are available that have overcome earlier problems associated with the reproducibility of glass columns prepared in-house, electrical continuity issues with aluminium-clad capillary columns, column breakages of ∗ Corresponding author. Tel.: +44 01752 584553; fax: +44 01752 584710. E-mail address: pasutton@plymouth.ac.uk (P.A. Sutton). glass, high temperature silica and aluminium-clad columns [7]. HTGC is the required industry standard method for quantita- tion in petroleum wax analysis (ASTM D5442-93), boiling point distribution in crude oils and residues (ASTM D7169-11) and biodiesel analysis (ASTM D6584/EN 14105) for conformity (ASTM D6751/EN 14214). Whilst HTGC is useful where analytes are of known composition, or can be retention time matched to exter- nal standards, retention matching small peaks to larger external calibrants and the presence of unknown constituents in the chro- matogram, is problematic for the analyst. To some extent these problems can be overcome for each sample using bulk mass spectral analysis (e.g. for hydrocarbons [8]), with the HTGC peak order inferred from lower molecular weight analogues which may be amenable to analysis using gas chromatography–mass spectrometry (GC–MS). Some complementary bulk mass spec- trometric techniques used for this purpose, such as electrospray or atmospheric pressure chemical ionisation-MS [9,10], Fourier transform-ion cyclotron resonance-MS [11] or matrix assisted laser desorption-MS [12] are useful for identification of ionisable/polar neutral molecules but are unable to directly detect saturated hydrocarbons without chemical modification, can require matrix optimisation and may suffer significant signal suppression. Sim- ilarly, exploitation of peak ordering for identification of high boiling compounds using GC × GC techniques (FID detection) has been limited to around n-C 68 by column thermal constraints (370 ◦ C), and has yet to be interfaced at high temperature with MS [2,3]. 0021-9673/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.chroma.2012.04.044