Our recent observations have shown that labs are showing an increased interest in converting their GC carrier gas from helium to hydrogen. Beyond the potential savings – hydrogen now costs a fraction of helium on a per-cylinder basis – with appropriate method translation the chromatography is almost always faster, with the same or higher resolution. Cylinder use has the downsides of safety concerns about the flammability of hydrogen, hidden costs (demurrage), storage space, and the possibility of instrument downtime during cylinder changes
High-purity gas is essential for the best GC results. Many point-of-use gas purifiers are available on the market to clean lower grades of gas to carrier grade gas. The point-of-use purifiers come in all kinds of sizes, prices and (claimed) capacities. Are you getting your money’s worth with the purifier you’re using?
We’ll focus on oxygen-removal capacity in this blog, because oxygen is usually the most damaging common contaminant for stationary phases. So a purifier’s capacity for oxygen is a good place to start when judging its value (cc’s oxygen removed per dollar could even be a way to produce a numerical comparison). Since we make gas purifiers at CRS, we test our own to make sure they meet product claims, and we occasionally review competitor’s purifiers. Amazingly, we’ve often found that actual capacities of name-brand purifiers can come nowhere close to their claimed capacity.
Let’s take a look.
How to determine O2-removal capacity
It’s easy to measure a gas purifier’s capacity for oxygen when it has a built-in indicator. Simply flow a gas standard through it with a known concentration of oxygen, then wait for the indicator to change color. It’s more expensive to test purifiers that don’t have indicators, but still easy with appropriate equipment. We use a Delta-F Nanotrace oxygen analyzer downstream of the purifier to measure efficiency of removal to sub-ppb levels, and simultaneously capacity.
Tuoteuutuudet laboratorioille. Tutustu kuvastoon tästä (pdf).
Steriilit, kertakäyttöiset puhdastilahaalarit. Haalarit ovat mukavat päällä ja suojaavat mainiosti. Valmistettu kestävästä, vähänukkaisesta ja staattista sähköisyyttä ehkäisevästä CleanTough™-kankaasta. Hihansuissa peukalon yli asetettavat remmit.