Speed Up Semivolatiles Analysis Without Sacrificing Critical Separations Using the EZGC Method Translator and a Narrow Bore Rxi-SVOCms Column

My last blog highlighted the importance of the indeno[123-cd]pyrene-dibenz[ah]anthracene separation with a promise to improve runtimes without sacrificing critical separations. More importantly, we maintain the same elution profile of the original 16-minute run. The EZGC method translator conveniently translates the acquisition parameters for one column format to another while preserving the analyte elution temperatures and relative retention times.

Using the parameters from GC_EV1604, the 8270 MegaMix chromatogram on a 30 m x 0.25 mm x 0.25 µm Rxi-SVOCms column (cat #16623), we can use the EZGC method translator to generate acquisition parameters for a 20 m x 0.15 mm x 0.15 µm Rxi-SVOCms column (cat #46616). The EZGC Method Translator interface is shown in Figure 1. It is important to select ‘Translate’ in the Results section; this insures an accurate flow translation.

Figure 1 - Translation from a 30 m x 0.25 mm x 0.25 µm column to a 20 m x 0.15 mm x 0.15 µm column using the EZGC Method Translator

Completing the analysis in 70% of the time while maintaining the elution profile sounds too good to be true, but it’s possible because the 30 m x 0.25 mm x 0.25 µm and 20 m x 0.15 mm x 0.15 µm columns used have very similar efficiencies. Both columns have more than 130,000 plates (at least theoretically). Let’s see how theory holds up under real testing conditions. Figures 2 and 3 are 8270 MegaMix chromatograms collected on the 30 m cat# 16623 and 20 m cat# 46616 Rxi-SVOCms columns respectively.

Figure 2 - 8270 MegaMix on the 30 m x 0.25 mm x 0.25 µm Rxi-SVOCms column

Figure 3 - 8270 MegaMix on the 20 m x 0.15 mm x 0.15 µm Rxi-SVOCms column

Even more impressive, the elution profile and critical separations shown in Figure 3 are very close to those predicted by the Pro EZGC chromatogram modeler (Figure 4). Take note of the oven program required for this analysis (35.6ᵒC/min to 285ᵒC and 28.5ᵒC/min to 330ᵒC); 110v Agilent GCs may require the GC Accelerator oven insert kit (cat# 23849) to reach these rates consistently. We recommend using a 20:1 split with column IDs ≤ 0.18 mm ID. This yields equivalent performance to a 10:1 split on a 0.25 mm ID column using the same inlet liner and calibration standards.  The 2 times higher split ratio will also give you 2 times less column contamination which may extend lifetime when comparing columns when the same number of samples are analyzed.

Figure 4 - 8270 Appendix IX calibration kit modeled on Rxi-SVOCms column cat# 46616 using the Pro EZGC Chromatogram Modeler.

Sacrificing a little efficiency (about 15,000 plates), we can translate to the 20m x 0.18 mm x 0.18 µm Rxi-SVOCms column (cat# 46602) using the EZGC method translator (Figure 5). This results in a benzo[ghi]perylene elution time that is 5.6 minutes earlier than what we see on the 30m Rxi-SVOCms column (Figure 6). The GC accelerator kit is almost certainly required for 110v Agilent GCs at these higher ramp rates.

Figure 5 - Translation from a 30 m x 0.25 mm x 0.25 µm column format to 20 m x 0.18 mm x 0.18 mm using the EZGC Method Translator.

Figure 6 - 8270 MegaMix chromatogram acquired on a 20 m x 0.18 mm x 0.18 µm Rxi-SVOCms column (cat# 46602)

Combining the GC Accelerator with a 208v (or higher) fast ramping oven allows you to use speed optimized flow translations for semivolatiles analysis that takes less than 10 minutes, but that topic deserves its own article.