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Large Volume Splitless Injection for EPA Method 522: 1,4-Dioxane in Drinking Water

  • Chris Rattray
  • #Blogs
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  • An abridged copy of the application has been published in the June 2012 edition of the LC|GC Application Notebook
  • The full application note can be found here

This past January, the EPA revised its 1,4-dioxane advisory, lowering it from 3.0 µg/L to 0.35 µg/L, a near 10-fold drop, and we’ve been seeing an increase in requests for 522 solutions. I interrupted my ongoing work with 8270 for a couple days to look into EPA method 522, 1,4-Dioxane in drinking water.

Using Jack and Michelle’s work with Large Volume Splitless Injection for semi-volatiles (which can be found here, here, here, and here), I’ve demonstrated that the same basic principles can be applied to the volatile compounds found in Method 522. With a few simple changes, any relatively modern GC/MS equipped with a standard split/splitless injection port and a fast injector can be used. I’m limiting this to relatively modern because I haven’t tried a HP 5971/5972 yet.

When I say a few simple changes, I'm not exaggerating. I took the 7890a/5975c that I’ve been using for 8270/525 methods, replaced the 10uL SGE autosampler syringe with this 25µL SGE autosampler syringe. I also took an angled press-tight connector and connected a 5 meter segment of our Rxi deactivated guard column to one of our new Rxi-624Sil MS columns (the 624Sil columns have a much higher maximum temperature and much lower bleed than the previous generation of 624 columns). I’ve never really liked how guard columns can be inconvenient to deal with in the cramped confines of the GC oven, requiring high temperature string and the tying and untying of knots, so I went ahead and wound the guard column into the column cage. These new cages make it much easier to keep the GC oven tidy.

If you don’t like the hassle of guard columns and press tight unions, we do have an Rtx-624 with a 5m integrated guard column, called an Integra-Guard™. I ran this column first, and obtained near identical results between the two analytical columns. If you don’t foresee a need for a high temperature volatile column, like high temperature bake-outs after an 8260 or 624 run, then the Rtx-624 w/5m Integra-Guard™ is an excellent solution. The important thing is that you have the 5m retention gap.

I calibrated using a standard concentration range of 1 ng/mL to 1000 ng/mL with excellent linearity. The extraction procedure using the method specific SPE tubes provides a 50x concentration, resulting in a theoretical detection limit of 0.020 µg/L. or 20 parts per trillion. I haven’t begun to optimize the instrument for higher sensitivity yet. I’d love to hear from you if you have any suggestions or would like to duplicate the work.

low level Rxi-624Sil MS detailed quant files

low level Rtx-624 detailed quant files

To recap, all this method modification requires is a larger autosampler syringe and a 5m retention gap (which can be purchased as an integrated part of your analytical column). Don’t forget to check section 9.4 of EPA Method 522 to review the QC requirements for modifying the method.