Basics of LPGC/Vacuum GC for fastest methods using the MS detector

Fast gas chromatography (GC) using mass spectrometry (MS) has always been challenging as we have to use a column with sufficient restriction under vacuum-outlet conditions. Short 0.10mm columns will work, but are practically challenging to work with in regards to injection and capacity.

In 2001 a new concept was presented for speeding up GC-MS analysis using short 0.53mm capillary columns (directly connected at the MS inlet) connected to a restriction column at the inlet, enabling a high vacuum inside the 0.53mm analytical column. Technique is known as LPGC (Low Pressure Gas Chromatography) or sometimes called “Vacuum GC”. Under the conditions created, very fast separations were performed as the optimal carrier gas velocity is a function of the actual pressure inside the capillary. Typically 3x shorter run times are obtained. We trade here some efficiency in for speed and robustness. Since a MS detector is used, no need full chromatographic separation is required. This technique was immediately adopted by Lehotay for fast pesticide screening. An optimized column for LPGC was developed and commercialized.