> ...

"1 nanomole of polyethylene" requires you to pick an arbitrary average molecular weight.

This changes the answer by orders of magnitude depending on what you pick.

Which is why nobody does it.

> Relatively little quantitative science in this area depends on counting plastic particles in microscopic images...Many others use methods that depend on gas chromatography or NMR.

So we're dismissive of some subset of papers, because they get false positives using toy methods.

Real science would use gas chromatography.

But...the paper we're dismissing tested gas chromatography. And found the same false positive. [1, in abstract]

> A relatively infamous recent example used pyrolysis GCMS to make low-concentration measurements (hence: nanomolar)

The brain study I'm guessing you are referring to, [2], measured low concentrations, yes.

But it reported them in ug/g.

Because polymers don't have a defined molecular weight.

> made idiotic claims about plastic spoons in brains

The brain study I'm guessing you are referring to, [2], does not mention spoons, or, come close.

Are we sure there's a paper that did that?

[1] Witzig et al, https://pubs.acs.org/doi/10.1021/acs.est.0c03742, "Therefore, u-Raman, u-FTIR, and pyr-GC/MS were further tested for their capability to distinguish among PE, sodium dodecyl sulfate, and stearates. It became clear that stearates and sodium dodecyl sulfates can cause substantial overestimation of PE."

[2] Campen et al, https://pubmed.ncbi.nlm.nih.gov/38765967/, "Bioaccumulation of Microplastics in Decedent Human Brains"