alt Hacker NewsI had strong echoes of a naieve lab experience in the 1970s: testing for organophosphates in seawater at the Forth Estuary was basically impossible except for gross amounts, because the standard analytical glass washing we used contaminated the glassware. You have to maintain a completely independent suite of glassware from pipettes all the way through to reaction vessels, and chromatography cells, and wash them with chromic acid, or special formulations.
(I don't work in this field any more, I was a lowly bottle washer and lab tech on a job creation scheme, I am sure the field has moved forward)
Similar issues plagued tests of iron concentration in seawater. Sample collection was contaminating the samples for years, until a procedure to collect a non-contaminated sample was developed by John Martin. He was able to finally figure out that actually most ocean water was iron deficient (that is to say: iron was the limiting factor in phytoplankton growth). Testing for environmental contaminants, especially in things that are commonly used by human civilization is really tricky.