Sample loading capacity for PAHs, part 3: 30m x 0.32mm x 0.25µm Rxi-5ms

My last post, “Does a thicker film GC column increase sample loading capacity for PAHs? 30m x 0.25mm x 0.50µm Rxi-5ms”, generated some interesting internal discussions between me, Jaap de Zeeuw, Chris English, and Chris Rattray, as to what constitutes overload of a GC column.  Jaap really focused on peak shape and contested my assessment that there was not a “substantial” difference between the 0.25mm x 0.25µm and 0.25mm x 0.50µm columns as regards overload, particularly for the 50 and 25 ng each PAH chromatograms.  So in addition to presenting PAH overload results for a 30m x 0.32mm x 0.25µm Rxi-5ms, which is also supposed to have increased sample loading capacity because of its wider bore, I zoomed in on the benzofluoranthene peaks for 50 and 25 ng amounts on column at Jaap’s suggestion for better inspection of the peak shapes.  So check out the first two sets of chromatograms below, which include 3 chromatograms each for 30m x 0.25mm x 0.25µm Rxi-5ms, 30m x 0.25mm x 0.50µm Rxi-5ms, and 30m x 0.32mm x 0.25µm Rxi-5ms columns.  The peak shapes do not look that much different to me, except for what appears to be a slight proportional narrowing of peaks for the 0.32mm x 0.25µm column with 25 ng PAHs, but perhaps readers can offer their opinions.

The next four sets of chromatograms demonstrate to me that there is still no dramatic increase in sample loading capacity for these PAHS with either a thicker film (0.25mm x 0.50µm) or a wider bore (0.32mm x 0.25µm) column. Essentially, these larger ring PAHs are just not “soluble” in the 5% diphenyl stationary phase, leading to overload, except at lower levels.  So up to this level of data collection, I still recommend the 30m x 0.25mm x 0.25µm Rxi-5ms GC column for semivolatiles/EPA PAH work because of faster run times, better separations, and narrower peak widths (which leads to better detectability).

As previously, the 30m x 0.32mm x 0.25µm method was translated from a previous method using the EZGC Method Translator.

Overload 3 Fig 1

Overload 3 Fig 2

Overload 3 Fig 4

Overload 3 Fig 5

Overload 3 Fig 6

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