Fast gas chromatography using vacuum outlet conditions

In this study the possibility of operating a wide-bore column with an inner diameter of 530 mum at vacuum conditions was investigated as a route towar ds fast gas chromatography. High analysis speeds can be obtained as a resul t of the sub-ambient pressure conditions present in the column, and the con sequently high diffusion coefficient of the solute in the mobile phase. The advantage of using a wide-bore column is the high sample capacity. To enab le vacuum operation through coupling a wide-bore column to a mass spectrome ter, three types of restricting the column flow were investigated. The firs t method uses narrow bore pre-column (60 cm length X 100 mum i.d.), the sec ond method relies on the use of a tapered on column supercritical fluid chr omatography restrictor (SFC-restriction), whereas the third method makes us e of a micro-injection valve. It was concluded that the best performance wa s obtained using the narrow-bore column restriction and the SFC-type restri ction. Analysis-examples in the seconds- and minutes-range are shown, with peak-widths ranging from 0.1 to 2 seconds at half height. It was concluded that with a film-thickness above 1.5 mum, the advantage of the increase in analysis-speed due to low pressures is nullified due to retention time incr ease on a thick film column. (C) 2001 John Wiley & Sons, Inc.