Fast Organochlorine Pesticide Analysis Using Hydrogen Carrier Gas with Split Injection GC-ECD
The world is getting faster, but I’m moving slower, about everywhere except my GC, where hydrogen carrier gas keeps me speedy. Take the organochlorine pesticides (OCPs) standard analyzed below with hydrogen carrier GC-ECD, which shows the 22 OCPs that are part of many EPA Method 8081 analyses separated in under 4.5 minutes. How can I do this? Well, first there’s the hydrogen itself, a faster carrier gas than helium or nitrogen, with excellent efficiency (no, I’m not going to show yet another van Deemter curve!). But just as important is the split injection, in this case 50:1, which allows a higher GC oven temperature start (180°C) without deforming the peak shape of the early eluting compounds (including TCMX). Finally, the Rtx-CLPesticides GC column has excellent selectivity for organochlorine pesticides, allowing a simple (but fast) linear oven temperature programming rate while still doing all separations almost to baseline.
OK, great, you showed us what may be a world record separation for those pesticides on a 30m x 0.25mm x 0.25µm column, Jack, but is there anything practical here when using such a high split ratio? Sure, because the µ-ECD is extremely sensitive I can do a calibration from 2 to 200 pg/µL (40 fg to 4 pg on column) and still have some room at the bottom. Check out the calibration curve for Lindane and the excellent detectability I have for 40 fg BHC peaks! And it may not be completely obvious because the results are so tight, but there were triplicate analyses done at each calibration point. Thank you, Restek Premium Precision® split liner with wool!
Finally, when doing an analysis this fast, the GC oven temperature equilibration time, if set to 1 min, which is what I used for most of this work, can itself reduce turnaround time. So I made seven replicate injections of a standard with ZERO as the oven temperature equilibration time to verify that this would not have a deleterious effect on retention time repeatability. As you can see in the chromatogram below, it didn’t.
There is another HUGE benefit to doing OCP work with split injection, which is the subject matter for my next OCP blog. I will send a five-pack of Restek Premium Precision split liners with wool for Agilent GCs to the first commenter on this post that correctly notes this Advantage.