Jack Cochran

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Vacuum Ultraviolet Absorbance Spectra – When a Little Means a Lot

Posted by Jack Cochran on March 27, 2017

Hopefully you read my last blog post on using vacuum ultraviolet (VUV) spectroscopy as a powerful detection means for gas chromatography (GC) of terpenes.  If so, you may remember that where VUV shines (a little spectroscopy joke for you) is producing unique absorbance spectra for the various terpenes, even isomers.  Unique spectra are what allow deconvolution of coeluting GC peaks, something I know a bit about from working with time-of-flight mass spectrometers. In mass spectrometry (MS), a (mostly) unique m/z ion for each coelutingcompound is what allows a mathematical routine to get going for deconvolution, followed by plotting apexing m/z ions for each coeluting peak to get its true spectrum.  That logic has always been easy for me to wrap my mind around.  It’s also simple to see how that same MS deconvolution approach fails for coeluting isomers since isomers have essentially identical mass spectra. 

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Building the VUV Entourage in Terpene Analysis

Posted by Jack Cochran on March 01, 2017

By Jack Cochran, Senior Director of Applications, VUV Analytics, Cedar Park, Texas, USA.

In a recent “In My View” article I wrote for The Cannabis Scientist, which is a “mini magazine” from The Analytical Scientist, I posed the question on whether it was more appropriate to analyze pesticides in cannabis samples using GC-MS/MS or LC-MS/MS.  Given the expense of capital equipment and the skills needed to operate it, this is not a trivial question.  However, the answer is made simple by considering one important thing, especially for medical marijuana: consumer safety.  To cover the full range of pesticides that are either currently used or have already been detected on cannabis, you need both techniques.  This doesn’t come as any surprise to analytical chemists analyzing residues on food, where GC-MS/MS and LC-MS/MS are routinely employed as complementary techniques to screen for hundreds of pesticides.

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