Switching to alternate carrier gases or conserving helium,
which is right for you?
With helium shortages a reality, chromatographers have a choice: either switch to an alternate carrier gas or find a way to conserve precious helium.
Switching to an alternate carrier gas
For successful GC analysis, the goal of conversion to an alternate gas should be to change the carrier gas without altering other method conditions, such as the column of the oven program. Accomplishing this requires adjustments to the column flow or holdup time to maintain peak elution order and peak retention times (or as close as possible). Maintaining chromatographic performance minimizes changes to timed integration events and to the peak identification table, thereby facilitating method revalidation. Agilent OpenLAB CDS provides method translation tools that help guide operators through adaptation of helium methods to alternate carrier gases.
Hydrogen is inexpensive. It can enhance chromatographic efficiency and reduce run times, but concerns about safety can outweigh these benefits. Successful migration to hydrogen requires a clean gas source (preferably > 99.9999%), use of a gas filter to remove water and oxygen, plumbing systems with chromatographic quality stainless steel tubing, and proper exhaust venting of split and septum purge vent flows – and possibly leak detectors.
Nitrogen is readily available, inexpensive, and safe. When compared to helium and hydrogen, nitrogen actually provides the best efficiency, but at a slower speed. Even at higher flows, nitrogen can still provide “good enough” resolution, especially for simple routine GC analyses. Many HPI GC methods can be easily adapted to using nitrogen as the carrier. It is also well suited to 2-D GC applications that use two columns to solve peak resolution issues. Nitrogen would not be suitable for GC/MSD and certain GC detector applications.
Conserving helium when an alternate carrier gas is not an option
Sometimes the time and cost required to revalidate method performance makes switching from helium to hydrogen or nitrogen difficult or impossible. That’s when using helium conservatively becomes especially important. Conserving helium not only extends the lifetime of existing supplies, but also reduces operating costs and ensures business continuity.
When instruments are not running samples, operators often maintain them in an operational mode with the heated zones hot and the inert carrier gas flowing through the system. This idle condition represents a major source of helium waste, so substituting hydrogen and nitrogen when the instrument is idle can save a great deal of helium – and money.
The best way to alternate between gases is to use a switching device that seamlessly delivers either helium or nitrogen to the GC flow control modules and integrates automatic and programmable helium conservation into daily operations. The Programmable Helium Conservation Module in the new Agilent 7890 GC system has a sleep/awake feature that completely automates operation of the helium conservation module. Operators create and save a sleep method that uses nitrogen carrier gas when the instrument is idle and an awake method that uses helium carrier gas. Using programmable helium conservation in conjunction with the gas saver features available with the 7890B GC considerably extends tank life and reduces laboratory dependence on helium deliveries.
Learn more
For additional information regarding method translation and helium conservation, please visit the Agilent Helium Update Page
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