We have a very bright guy named Jaap de Zeeuw who works for Restek. Years ago he invented a system for low-pressure gas chromatography by where he used a 0.53mm GC column attached to a mass spectrometer, and a restrictor column (e.g. 0.50m x 0.10mm) press-fitted to that column and installed in a split/splitless GC inlet. This restrictor allowed for a helium head pressure to be maintained on the inlet while the 0.53mm column was operated at sub-ambient pressure. The low column pressure shifts the carrier gas optimum linear velocity higher, which means faster analyses without a loss in efficiency. And, you get the benefit of high capacity from the 0.53mm column.

I recently used low-pressure GC-TOFMS on a LECO Pegasus instrument as part of a project directed by my colleague, Amanda Rigdon, to characterize synthetic cannabis, a blend of herbs that is sprayed with cannabinoid mimics (e.g. the JWH compounds like JWH-018) and marketed as “incense” (e.g. Spice, K2, Voodoo Child, Puff, Tribal Warrior, etc.). This incense is smoked by a user to achieve a high, not completely unlike that from smoking marijuana.

Synthetic Cannabis (Wikipedia)

The GC analysis of these compounds, due to their relative involatility and sometimes active functionalities, is not trivial. In fact, for some GCxGC work we did, the analysis times on a 15m x 0.25mm x 0.25µm Rxi-17Sil MS primary column were about 50 min. Low-pressure GC-TOFMS allowed much quicker run times, and produced peak widths on the order of 2 sec, which helps with sensitivity.

Check out the low-pressure GC-TOFMS analysis of a 12 component mix of synthetic cannabinoids obtained from Cayman Chemical (Ann Arbor, MI, USA). Complete in < 10 min!

Cayman Chemical Synthetic Cannabinoids

Many thanks to Paul Kennedy at Cayman Chemical for help with this project and to Scott Grossman of Restek for providing the drawing of a low-pressure GC system.

Low-Pressure GC-TOFMS of Synthetic Cannabinoid Standard from Cayman Chemical

Zoom of Low-Pressure GC-TOFMS Chromatogram of Synthetic Cannabinoids

This entry was posted on Tuesday, November 2nd, 2010 at 5:29 pm and is filed under Drugs of Abuse, GC/MS, Optimizing Applications, Tips & Tricks. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.