I try to learn everything that I can about analytical testing. Not being a scientist and only being a lawyer, I am an outsider to this fascinating world. I find that as I learn more, more questions present themselves. As an outsider last year l learned something that really kind of surprised me.
When Gas Chromatography is used and especially when an auto-sampler for Headspace Gas Chromatography (HSGC) is used, there is no universal standard operating procedure as to what headspace vial goes into what position and what minimum standards comprise a auto-sampler Headspace Gas Chromatography run.
(above video an auto-sampler)
But why does this matter?
As a nationally known DUI attorney and having received forensic expert training, I get weekly calls from colleagues from Georgia, Tennessee, New Hampshire, California, Arizona and elsewhere about Gas Chromatography. I love it. I thank my colleagues for the trust in consulting with me. It is amazing to me to see the variation. The variation is not only from state to state, but also from labs within a state and yes, even from technicians within one lab. Wow!
So if there is no uniformity, then there can be no consistency. There are large issues that can emerge with this approach. I have personally seen the following:
- An entire run without a single blank (Pennsylvania)
- An entire run without positive controls (New Hampshire)
- An entire run without a separation matrix that would prove separation between methanol, ethanol, isopropanol or butanol at the very least (Georgia, Tennessee)
- No calibrators within the run (Texas)
- A "historical calibration curve" used as a calibration curve where the columns were actually replaced between the columns that produced the "historical calibration curve" and the columns that were used to test this unknown (Pennsylvania)
- A lack of blanks run between unknowns to prove lack of carry-over effect (everywhere) [Blogger’s note: a more comprehensive post on this will follow]
-Justin J. McShane, Esquire, Pennsylvania DUI Attorney
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8 responses to “A large problem in Gas Chromatography: No uniform standard for GC run position or composition”
Attorney Mark Stevens says:
This is a great article Justin. I bookmarked it for reference. Best of success in your upcoming battles.
Gas Chromatography says:
It was just super information sharing and I am thankful to your for sharing that.