Standard on-column injection: A fast and simple method for large volume injection in medium-resolution gas chromatography

In gas chromatography (GC) large volume injection of samples containing ver y high molecular weight analytes presents unique problems. Standard program med-temperature vaporizing or on-column large volume injection systems cann ot be used, mainly due to instrumental difficulties. A new, simple solution to this problem is presented. If short, wide-bore columns are used at carr ier gas velocities above optimum, the cloud of vapor formed upon evaporatio n of the solvent can be rapidly discharged from the system by the column fl ow alone. Hence, in medium-resolution GC, large sample volumes (e.g., 50 mu L) can be injected using a standard on-column injector. Neither a retention gap nor a solvent vapor exit is needed. The absence of column connectors m akes this setup extremely rugged. The optimization of the direct on-column large volume injection is described. The applicability of the new technique for the injection of large volumes of triacylglycerides and heavy mineral oil fractions is shown. It is demonstrated that the new technique is relati vely insensitive toward solvent composition. This makes the new method emin ently suited for combination with gradient liquid chromatography preseparat ions. (C) 2000 John Wiley & Sons, Inc.