We use 2,3-dibromopropionic acid as our surrogate and lately it has been giving us fits. It falls out of the +- 30 % range often in our samples, and usually runs low in our calibrators, where the HAA's respond well.
I thought the problem would be solved by replacing the columns ( DB-XLB + DB-35MS), but it didn't change much.
We use MTBE and derivatize for 210 minutes at just over 50C on a hot block, and quench with 4 mls. of saturated bicarbonate.
Any insights as to how to resolve this issue?