>traces that will be concentrated at the top of the food chain (which is us) Also when trace analysis becomes more sensitive or focused as technology advances,

>traces that will be concentrated at the top of the food chain (which is us) Also when trace analysis becomes more sensitive or focused as technology advances, alarms can be raised over things which were never detectable in the past. These operators seem to have sophisticated instruments optimized for this type of pursuit. I also use very capable gear, but mainly for leading industrial chemical analysis over the last 4 decades. No biology involved, but very many kinds of chemical companies. And I've got news for them. Very few pure reference materials are actually available even to the major manufacturers' chemical plant or research labs. What they would like to have made into "analytical standards" for absolute confirmation I would like too. Oh well. So I spend decades improving my abilities to make my own, if I don't do it who will? That's one reason we even have mass spectrometers on the bench to begin with, to work around that little snafu. Regardless, it can take a while to get good enough for your results to be worth money. For instance when MTBE was a thing, I was able to report to clients more details of what was in their purchase than the producing oil & chemical companies themselves were able to do, but not nearly as well the first year as it was after that.