Last month in San Pedro Bay we deployed 12 POCIS and 6 SPMDs for 14 days, paired LC-HRMS suspect screening with a sea urchin embryo assay, and the bioeffect signal exceeded what the quantified PAHs and PFAS would predict. What tools or prep are you relying on to pin down toxin-metal interactions and matrix effects — passive samplers that span polar/hydrophobic species, mixed-mode SPE to cut humics before HRMS, or portable reporter assays that behave in high DOC?
I’ve had luck splitting the POCIS/SPMD extract and doing an ‘EDTA challenge’ before the urchin embryos: add about 1 mM EDTA for 10–15 min at room temp, rerun, and if the signal collapses it points to a metal–organic interaction; caveat, at marine salinity EDTA can stress embryos, so desalt the extract or keep the spike low.
Quick example from San Diego Bay: co-deploy DGT with your POCIS/SPMD, then “fractionate first, assay second” — split the extract across HLB→SAX→SCX and run embryos per fraction; when the signal sticks to the SAX fraction and tracks DGT Cu/Zn, it’s usually a metal-mediated hit. Minor caveat: DGT can under-read in high DOC, so we log UV254/DOC alongside and confirm with a Chelex cleanup; brief primer here: https://www.dgtresearch.com.
We’ve pinned down Cu–ligand effects by adding a targeted rescue to the embryo wells — 1 µM BCS for Cu vs 0.5 µM TPEN for broader divalents, 10–15 min preincubation — and a rescued bioeffect with flat LC‑HRMS flagged complexation as the driver. > under-read in high DOC, so we log UV254/DOC alongside and confirm with a Chelex cleanup; brief primer — same here: we log UV254/DOC at pull times and give extracts a 2‑min Chelex pass so the rescue reads clean, @ellenM92; have you compared BCS vs TPEN side‑by‑side?
Chelex-100 cleanup on 14‑day POCIS/SPMD extracts rescued embryos; @heidij82 tipped me off — watch Zn‑organics.