Author(s): Yvette Naudé, Egmont R. Rohwer
Department of Chemistry, University of Pretoria, Private Bag X20, Hatfield 0028, Pretoria, South Africa
Published By: Journal of Chromatography A
Year of Publication: 2013
Abstract: Pinotage wine from several South African wine cellars has been produced with a novel coffee flavour. We have investigated this innovative coffee effect using in house developed solventless sampling and fractionating olfactometric techniques, which are unique in their ability to study synergistic aroma effects as opposed to traditional gas chromatography olfactometry (GC-O) which is designed to, ideally, evaluate single eluting compounds in a chromatographic sequence. Sections of the chromatogram, multiple or single peaks, were recaptured on multichannel open tubular silicone rubber (polydimethylsiloxane (PDMS)) traps at the end of a GC column. The recaptured fractions were released in a controlled manner for offline olfactory evaluation, and for qualitative analysis using comprehensive gas chromatography coupled to time of flight mass spectrometry (GC×GC–TOFMS) for compound separation and identification, thus permitting correlation of odour with specific compounds. A combination of furfural and 2-furanmethanol was responsible for a roast coffee bean-like odour in coffee style Pinotage wines. This coffee perception is the result of a synergistic effect in which no individual compound was responsible for the characteristic aroma.
Acknowledgment(s):We wish to thank Gerhard Overbeek for assisting in the extraction of wine and aroma evaluation, Phakama Botha for assistance in wine extraction, Dr Fanie van der Walt for the custom-built olfactometer, David Masemula for the assembly of multichannel PDMS traps, Dr Peter Gorst-Allman from LECO Africa (Pty) Ltd. for use of a LECO Pegasus 4D GC×GC–TOFMS, Philip Langenhoven from LECO Africa (Pty) Ltd. for sponsorship, Jack Cochran from Restek for kind donation of GC columns and consumables, SASOL and the National Research Foundation (NRF) for financial support.
Restek has developed a GC column specifically for the analysis of polycyclic aromatic hydrocarbons (PAHs) in food safety and environmental samples. The new Rxi®-PAH column features a higher phenyl-content stationary phase that provides a unique selectivity to separate important PAHs that cannot be distinguished by mass spectrometry. Even difficult priority compounds, such as the European Food Safety Authority (EFSA) PAH4, are easily separated and accurately quantified, results that cannot be achieved on typical GC columns. The selectivity and efficiency of the Rxi®-PAH column make it ideal for EFSA PAH4 analysis; chrysene triphenylene separation and resolution of all benzofluoranthenes are easily achieved. Excellent column efficiency means critical PAH separations can be maintained when the column is trimmed. In addition, the rugged, arylene-modified stationary phase is stable up to 360 °C, which ensures that relatively nonvolatile, higher molecular weight PAHs, such as dibenzo pyrenes, can be analyzed routinely without interference from column bleed. Separation of benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[a]pyrene, and other PAH compounds make Rxi®-PAH columns ideal for EFSA PAH4 analysis, as well as other environmental and food safety testing. Visit www.restek.com/rxi-pah for product details.
Author: Jaap de Zeeuw
Published By: Chromatography Today
Issue: November / December 2012
Year of Publication: 2012
Abstract: Hydrogen is on the agenda again. Since the supply of helium has become a challenge, many labs are now considering the use of hydrogen as the carrier gas of choice. Most chromatographers agree that hydrogen is the best choice,because of the advantages on analysis time and availability, but safety management issues are the primary concerns with many chromatographers. Hydrogen can be generated safely in the lab and if you make the calculations, you will find that commercial gas generators are cost effective and will pay for their purchase price in a relative short time, particularly since the price of helium is high and unlikely to come down in the future. The focus of this paper will be to investigate the practical impact of using hydrogen in the lab and what other aspects need to be considered.