46 CHROMATOGRAPHY
From helium to hydrogen
Jack Cochran explains how to optimise for speed or match your original compound retention times via the use of a novel translator.
Fig. 1. Get the same separation in nearly half the time by using Restek’s EZGC software to properly convert instrument conditions when switching from helium to hydrogen carrier gas.
W
hen discussing the conversion of GC methods from
helium to hydrogen carrier gas, generally the focus is on speed as hydrogen has a higher optimal flow rate than helium and can be used to achieve faster run times without sacrificing separation efficiency.
While speedier analysis times offer the attraction of improved productivity, there are times when matching the original compound retention times is more important, for example, to make calibration updates or new method validation easier.
Regardless of whether the goal is faster analyses or maintaining the original compound retention
Fig. 2. To quickly determine conditions for hydrogen that will maintain the retention times obtained when using helium, simply match the method holdup times in the EZGC program’s custom mode.
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times, proper method translation is critical for success. Te new EZGC method translator/ flow calculator from Restek is an easy-to-use tool that ensures proper conversion from helium to hydrogen for either speed optimised or matched retention time scenarios.
Increase sample throughput with faster separations Obtaining faster GC run times so more samples can be analysed in a day is often the driving force behind converting from helium carrier gas to hydrogen. With proper method translation, this can be an easy way to improve productivity and reduce dependence on expensive and increasingly scarce helium.
Te conversion requires a faster GC oven program rate for hydrogen versus helium to maintain the same chromatographic elution
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