Seeing HAAs on as18 column

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I run a dionex 2100 with an AS18 column for anions. I noticed in many chlorinated samples seeing a peak with RT about one minute after chlorate. I suspected that it was trichloroacetate so I asked the organic guy to give some samples that tested positive for TCA. When I ran them I saw this post-chlorate peak in every sample. I then ran a mixed HAA standard and saw the peak there. I saw 9 peaks in the HAA standard and some of them match with other mystery peaks I have observed in other samples. Is anyone else seeing haloacetic acids on columns designed for inorganic anions?
anionman wrote:
I run a dionex 2100 with an AS18 column for anions. I noticed in many chlorinated samples seeing a peak with RT about one minute after chlorate. I suspected that it was trichloroacetate so I asked the organic guy to give some samples that tested positive for TCA. When I ran them I saw this post-chlorate peak in every sample. I then ran a mixed HAA standard and saw the peak there. I saw 9 peaks in the HAA standard and some of them match with other mystery peaks I have observed in other samples. Is anyone else seeing haloacetic acids on columns designed for inorganic anions?


You will see those really well on the anion columns. In fact EPA Method 300.1 uses DCAA as the system monitoring compound to monitor recovery and it elutes near chlorate and bromide.
The past is there to guide us into the future, not to dwell in.
If you use a gradient elution on the AS18 column; the monochloroactate elutes right on top of chloride. And on my system (using KOH gradient) the dichloracetate elutes very close to chlorate.
I don't have any single HAA standards, which makes it hard to identify which peaks are which HAAS. I have one very large peak that is very close to chloride - only 0.1 minute later than chloride. Another peak is only 0.05 minute later than nitrite. Another matched the RT for nitrate exactly. But nitrate is close to chlorate so maybe that's the dichloroacetate. There are 3 distinct peaks that elute after chlorate though. I suspect the last 2 peaks may be Bromoacetic acid and Bromochloroacetic acid.
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