Evaluation of an Improved Burner Design for a Flame Infrared Emission (FIRE) Gas Chromatography Detector

Abstract

Flame infrared emission (FIRE) measurements made at 4.4 μm have shown that changes in burner design have improved the sensitivity of the FIRE radiometer by approximately 1-1.5 orders of magnitude. The new burner consists of two concentric, stainless steel tubes. Air is introduced through the outer tube, while a mixture of GC effluent and hydrogen gas is introduced through an inner capillary tube. When the burner is used as a detector for gas chromatography (GC), optimization parameters were found to be the same for a variety of compounds, GC columns (packed and capillary), and injection volumes (0.1–2.0 μL). Since less hydrogen was required to produce a stable flame, flame background emission was greatly reduced, background subtraction was no longer required, and instrumental complexity was considerably reduced. The new FIRE-GC detector could be used in conjunction with capillary columns, thus permitting improved separation of more complex mixtures. A conservative estimate of detection limits (2σ), obtained with a mixture of benzene, butanone, 1-chloro-3-methylbutane, and methyl acetate, indicated that the new FIRE-GC detector had an average detection limit of 4.5 ± 1.3 ng s⁻¹ in terms of carbon. Response (μmoles of carbon) was linear over the entire range of concentrations tested, giving an estimated linear dynamic range of at least 3.4 orders of magnitude. The utility of the new FIRE-GC detector was demonstrated by an application involving the separation of a synthetic mixture of 16 compounds on a 15-m silica capillary column under programmed temperature conditions. The new burner responded well to halogenated, nonhalogenated, and aromatic compounds with boiling points in a range from 36 to 152°C.