GC-MS with Cold EI and its Unexpected Benefits

Aviv Amirav, Chemistry, Tel Aviv University, Tel Aviv, Israel
Alexander Fialkov, Chemistry, Tel Aviv University, Tel Aviv, Israel
Tal Alon, Chemistry, Tel Aviv University, Tel Aviv, Israel
Uri Keshet, Chemistry, Tel Aviv University, Tel Aviv, Israel
Svetlana Tsizin, Chemistry, Tel Aviv University, Tel Aviv, Israel
Boaz Seemann, Chemistry, Tel Aviv University, Tel Aviv, Israel

GC-MS with Cold EI is based on GC and MS interface with Supersonic Molecular Beams (SMB) and on electron ionization of cold sample compounds in the SMB (hence the name Cold EI) in a fly-through ion source. The GC eluting compounds are mixed with helium make up gas, expand from a supersonic nozzle into a vacuum chamber, vibrationally cooled, skimmed, collimated into a SMB, pass a contact-free electron ionization ion source and are ionized and mass analyzed.

GC-MS with Cold EI such as the Aviv Analytical 5977-SMB excels in improving all the major GC-MS operational parameters including sample identification, sensitivity particularly of difficult to analyze compounds, range of compounds amenable for analysis, speed of analysis and response uniformity.

GC-MS with Cold EI provides several unexpected important benefits including:  

A) Sample identification with single quadrupole based GC-MS with Cold EI is superior to any other GC-MS including with highest resolution MS. This is since with Cold EI bigger and more labile compounds elute, exhibit abundant molecular ions and provide elemental formula with our TAMI software.    

B) NIST library identification is actually improved with the Cold EI enhancement of molecular ions since the matching factors of other candidates are significantly reduced.   

C) Significantly extended range of labile, polar and low volatility compounds are amenable for analysis due to the ability to use short columns with high column flow rates that lower their elution temperatures.

D) Cold EI uniquely provides uniform compound independent ionization yield that serves for effective measurement of organic chemical synthesis yields, unlike with standard EI or electrospray LC-MS.     

E) Effective fast GC-MS analysis (<2 min analysis time) is achieved with column flow programming thereby providing probe analysis speed with separation information.

F) The same system can serve as GC-MS with Cold EI and Electron Ionization LC-MS.