The Column - April 2008 - (Page 10)

Incognito The Column www.thecolumn.eu.com April 2008 Gas Chromatography — A Technique on the Rocks? Following last month’s discussions on the possible practical limitations of so-called “Fast” HPLC, I have undertaken several discussions and some further research on the latest progressions in gas chromatography (GC) — I must admit I hadn’t considered just how “stale” GC has become as a technique! While it’s true that GC has advanced through “extensions” of existing technology, we have largely ignored the major issues — perhaps because the challenge is just too great? One major issue I have with GC is the way we control temperature, especially the GC column oven. Surely using a large “box of air” to control the heating and cooling of a GC column is primitive? I cannot believe that this cannot be done more effectively and efficiently, allowing us to significantly speed up column heating/cooling. Several manufacturers have attempted to overcome this problem; one notable approach uses resistive tape wrapped around the column, which is heated electrically. However, I cannot see the literature full of promising applications on how to use this technology to radically speed up or improve separations. Maybe the technology is not up to the job, or perhaps we have not paid it Don Farrall/Getty Images Author: Incognito E-mail: incognito@thecolumn.eu.com enough attention — write and let me know if you are successfully using such technology. The next area of concern is over sample introduction and the lack of foresight into the problems associated with transferring a liquid sample into a homogeneous gas phase representation of itself. I’m sure there must be better ways to get our samples into the gas phase without having to subject them to “ballistic heating” in an environment that is highly adsorptive to polar or chelating analytes. Why do inlet liners (sleeves) have to be made out of silica quartz or metal? Can’t we find anything heat resistant but also much less likely to bind to analytes, causing quantitative irreproducibility and poor peak shape? There are several alternatives to split/splitless injection, however, no-matter how hard I try, I have never been able to get many of these alternatives to work with good accuracy and reproducibility — but perhaps that’s just a personal failing? Furthermore, I speak with hundreds of GC practitioners every year, from undergraduate students to “method developers” and much less than 50% of them actually understand how to properly set up their GC injector regardless of type. Can you honestly say that you know how to optimize the splitless time in a splitless injection routine or that you truly understand how to optimize the “solvent vent” parameters when using a PTV injector? The amazing Grob family has done much to help us understand GC sample introduction but has anyone ever come up with a truly “alternative” injector design that can be directly GC mounted, is simple to understand and implement but which doesn’t suffer from thermal decomposition or quantitative losses through analyte adsorbtion or other discrimination processes? If you think you have overcome these problems let me know and we can market the inlet together! Anyone tempted to suggest “on-column” injection, stop and ask yourself if this injection method really meets all of the criteria above. I’m not so sure. Switching the consideration to GC columns, I have had several conversations with GC column manufacturers lately 10 http://www.thecolumn.eu.com

Table of Contents for the Digital Edition of The Column - April 2008

The Column - April 2008
Contents
News
Incognito - Gas Chromatography — A Technique on the Rocks?
On-Site Sample Preparation Using MEPS for Wastewater Analysis
Market Trends and Analysis
Tips and Tricks: GPC/SEC BEWARE of Mismatch
A Simple, Optimized Approach to Automated SPE
Q&A - Seeing Green

The Column - April 2008