BAC Analysis Using Hydrogen Carrier Gas: Get the Same Results at a Lower Cost!

Who doesn’t want the same thing they’re getting now at a lower cost, especially if historically that cost has only been rising? That question got me thinking about the 2012 SOFT meeting where I presented a talk about Restek’s new BAC Plus columns. A large portion of the talk focused on improving headspace chromatography of blood alcohol compounds by using a fast linear velocity and split injection technique. As you can see in Figure 1, going from a 5:1 split injection to a 20:1 split drastically improves peak shape without sacrificing much in the way of sensitivity. Note that these chromatograms were generated on the BAC Plus 2 column only – the same thing happens on the BAC Plus 1, I promise.

However, a 20:1 split injection on a 0.32mm ID column operating at 80cm/sec uses a 150mL/min of helium. A 0.53mm column operated in this manner uses a whopping 275mL/min helium. Wow! That’s a lot of helium! Unfortunately, since helium is becoming increasingly scarce, implementing this method change in your lab may be prohibitively costly or just plain impossible, depending on your helium supply. Fortunately, there’s a really easy way to get around this problem. There have been several other blog posts from my colleagues discussing the use of alternative carrier gases over the past few months, so that got me thinking: why not use a hydrogen carrier for blood alcohol analyses?

Usually, changing carrier gases for FID analyses doesn’t pose much of a problem – especially for isothermal FID analyses. In fact, the QC tests for the BAC Plus columns are run using hydrogen as a carrier gas. So I gave it a try and ended up with beautiful chromatography using exactly the same conditions that I was using for helium. Figure 2 shows my BAC run with hydrogen.

I used nitrogen as the pressurization gas for my headspace instrument. For obvious safety reasons, hydrogen shouldn’t be used as the vial pressurization gas. By performing a split injection, I’ve avoided any potential problems arising from injecting a large slug of nitrogen into the carrier gas stream.

It’s every chromatographer’s dream to have their analysis work on the first try, and it appears that switching to hydrogen worked that way. To date, I haven’t done any quantitative work with it, but it definitely seems like a viable solution. I would love to hear comments from labs who have tried this approach.

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