Abstract: A gas chromatographic method utilizes columns having either ascending or descending temperature profiles to effect separation even under column overloading conditions. A fixed ascending temperature profile column allows for good separation of components of a mixture under conditions of column overloading. A mixture to be separated is chromatographed on at least one such column prior to chromatography on a column maintained with a descending temperature profile. This latter column has surprisingly been found to greatly reduce tailing of less volatile species. The invention also includes a variable temperature descending column chromatography to provide an initial ordering of a large quantity of components prior to chomatography on the fixed ascending temperature profile column, or on the serial fixed ascending and descending temperature profile pair of columns.