504.1

[Bigbear]

Anyone still using this other than us?

I am curious if anyone uses an internal standard for this method?
If so what compound, and how (pre or post extraction)?

[James_Ball]

Anyone still using this other than us?

I am curious if anyone uses an internal standard for this method?
If so what compound, and how (pre or post extraction)?

We were doing it external standard, but in January we switched ours over to 524.3 using SIM for the more simple prep and fewer interferences.

[Bigbear]

I was considering 524.3, but QC and hardware requirements put me off. I would at least need to get a chilled vial sampler.
How do you preserve your samples? I found ( the hard way) that if you introduce thiosulfate into my system I get SO2 for ages!

[James_Ball]

For 524.3 we are using the Ascorbic Acid/Maleic Acid preservative. We do have the chiller on the autosampler and it helps with compounds like Pentachloroethane breakdown when running overnight. The QC is more difficult to hit where it requires the MRL level CCV at the beginning of the analysis, but it also only requires a +/-50% for that to pass.

We are doing the EDB/DBCP using SIM mode and don't have to push the multiplier very much to hit the limits listed in method 504 but we did drop the split to 60:1.

[vballchemist]

We still routinely do EPA 504.1. We do external standard calibration and use TCMX/DCB for surrogate recovery. The method does not require a surrogate but the STATE does.