I recently posted some chromatograms for our new EPA Method 541 UCMR4 Standards, and wanted to focus on the column in a separate post. EPA Method 541 was developed on a 30m x 0.25 mm ID x 0.50 µm wax column from another manufacturer. I used the Stabilwax because it is a relatively low bleed wax column and has similar selectivity to the column used by the EPA. My chromatogram is shown above, while a calibration standard chromatogram taken directly from the method documentation is shown below.
There are 2 major differences I wanted to point out:
- The Stabilwax column has the same elution profile but it is less retentive at the same phase ratio. The last target compound (chlorobenzene-D5) elutes on the Stabilwax at 8.66 minutes, which is BEFORE the 1st target compound (1,4-Dioxane) elutes on the column used in the EPA Method (10.3 minutes). UCMR4 does not include 1,4-dioxane, so it is not included in the Stabilwax chromatogram. The GC acquisition parameters were the same for both columns, though the detector settings were different because of the SIM window start times. All peaks had eluted on the Stabilwax before the method recommended solvent delay ended.
- The bleed is significantly lower on the Stabilwax compared to the calibration standard chromatogram from the EPA method.