Hi all-

We analyze phthalates by 625. We've now twice failed DEHP low (by a decent margin) in Sigma-Aldrich PE's. Looking back at the data, we noticed that the rest of the phthalates, while acceptable, were on the low end of the acceptable range. Our BS recoveries for diethyl and dimethyl phthalates have been low on average (30-40%) but the remaining phthalates recover around 70-75% mean - on par with most analytes in our BS samples. We use continuous liquid-liquid extraction with a Horizon dryvap for concentration.

Anyone had issues with low phthalate recovery? I feel a bit lost, as it seems unlikely that both our calibration standards and extracted samples (independent standard lot, same supplier) would be running low relative to other labs, and if anything I'd expect phthalates to run a bit high from background contamination.