VMS for when your TO-15 air lab is hazy, hot, and humid!

When it comes to analyzing volatile organic compounds (VOCs) in air canisters, it is no secret that my go-to-column is the VMS. I have raved about the VMS in the following pieces:

  1. The NJDEP-SRP Low Level TO-15 blog series
  2. My Favorite Column blog
  3. A white paper
  4. And some other articles I am forgetting…

You get the point! However, do you remember why I love my VMS so much? Well, we better just recap with the following reasons the VMS rocks:

  1. The polars (e.g., ethanol, IPA, etc…) look symmetrical (unlike all the other phases) with no hint of tailing.
  2. Butane and 1,3-butadiene are separated, which is a common coelution most air labs are completely unaware of.
  3. There is no clumping of compounds (i.e., everything is spread out across the entire GC run).

So why then today’s blog? What more could I say about the VMS (Quick Reminder: VMS = Volatile Mass Spec). Well, as you are sitting there in your hot pants (no shorts for this lab rat, because of EH&S attire rules), on this hot and muggy summer day, reading this blog; you may remember that all of my previous work on the VMS had GC oven starting temperatures from 32 – 35 °C. I know you do not want to wait the extra time as your GC oven struggles to cool from 40 down to 32. So, as the mercury rises today we show you the following:

  1. The complete resolution of 79 VOCs (75 targets and 4 internal standards) in 16 minutes; with all of the aforementioned awesomeness, but now with a 40 °C start temperature.
  2. The complete resolution of chloromethane and butane (a coelution discussed in the NJDEP-SRP Low Level TO-15 blog series).
  3. The complete resolution of hexane, MTBE, and TBA.
    1. IDK why, but Hexane always finds a way to try and coelute on the other phases. For example:
      1. Ethyl acetate and Hexane (1-type)
      2. MEK and Hexane (5-type)

Without further ado, Table I gives you all the pertinent Preconcentrator-GC-MS parameters; and Figures 1 – 3 and Table II shows the end result.

Table I – Preconcentrator-GC-MS Parameters

Figure 1 – 75 TO-15 VOCs and 4 ISTDs in 16 min

Table II – Compounds and Retention Times (RTs) * Internal Standard t Tuning standard


Figure 2 – Try to get your polars looking like that on a 1- or 5-type.

Figure 3 – You can drive a bus in between these peaks! And look at that TBA symmetry!

There you have it! Everything I normally brag about when using the Rtx-VMS for VOCs in air, but now with a 40 °C starting temperature. So, whether your scorching in Shanghai or roasting in Hotlanta, you no-longer have to wait forever to run your next canister sample as the GC oven cools.

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