GC–MS Leak Detection
Leaks in GC–MS are particularly insidious. How do you know when you have a leak and where do you start to look for it. It is something that will happen to all chromatographers at some point. Here is our quick guide to how to identify the source of GC–MS leaks.
Recently a CHROMacademy user contacted our experts as their GC-MS system was not maintaining vacuum.
Normally, the vacuum was set at 1.2x10-7 Torr; however, it was dropping to 2.3x10-4 Torr.
The user carried out some maintenance by tightening and then subsequently replacing the nut and ferrule at the transition line which solved the problem initially.
Unfortunately this did not fully remedy the problem. The source was capped and the pressure held, however, this still left the user scratching their head as to why they were seeing gross pressure drops.
The vacuum not holding in a GC-MS system would indicate a leak. Leaks in a GC–MS system can be particularly frustrating; they can cause spurious peaks in the mass spectrum, a decrease in sensitivity, loss of carrier gas (this could be expensive), and damage to the instrument.
Often leaks can occur where the column enters the MS or at point(s) where the vacuum system was disassembled and reassembled (i.e. for any routine maintenance operations). If it is expected that there is a leak in a GC-MS system there are a few things that can be done to try and identify the source of the leak in order to repair it.
1. When the system is running verify that peaks at m/z 28 and 32 are present in the mass spectrum. These peaks are indicative of nitrogen and oxygen; if they are present in a ratio of 4:1 (nitrogen:oxygen) this would indicate that there is a leak to the atmosphere. If the peaks for water (m/z 18), nitrogen (m/z 28), and oxygen (m/z32) rise above 10% (relative to m/z 69 peak — typical base peak from PFTBA used during auto-tune) this is also indicative of a leak.
The complete article is available to CHROMacademy Lite and Premier members here >>
CHROMacademy Lite Membership is FREE and it only takes two minutes to register.
With a Lite Membership you are given access to:
∙ This month's webcast & tutorial
∙ Selected eLearning modules
∙ Featured CHROMacademy Content
∙ The CHROMacademy forum
Test drive CHROMacademy and Check out more great content available FREE to our Lite members »
Best of the Week: Food Analysis, Chemical Migration in Plastic Bottles, STEM Researcher of the Year
December 20th 2024Top articles published this week include the launch of our “From Lab to Table” content series, a Q&A interview about using liquid chromatography–high-resolution mass spectrometry (LC–HRMS) to assess chemical hazards in plastic bottles, and a piece recognizing Brett Paull for being named Tasmanian STEM Researcher of the Year.
Using LC-MS/MS to Measure Testosterone in Dried Blood Spots
December 19th 2024Testosterone measurements are typically performed using serum or plasma, but this presents several logistical challenges, especially for sample collection, storage, and transport. In a recently published article, Yehudah Gruenstein of the University of Miami explored key insights gained from dried blood spot assay validation for testosterone measurement.
Determination of Pharmaceuticals by Capillary HPLC-MS/MS (Dec 2024)
December 19th 2024This application note demonstrates the use of a compact portable capillary liquid chromatograph, the Axcend Focus LC, coupled to an Agilent Ultivo triple quadrupole mass spectrometer for quantitative analysis of pharmaceutical drugs in model aqueous samples.
