A document I've been reading states that:
Both the Maximum Contaminant Level Goal and the Maximum Contaminant Level were set at 2 parts per billion because current technology allows public water suppliers to detect and remove mercury levels that low.
But I know of drinking water test strips that detect 0, 50, 100, ... 1000 ppb and are 1,5-Diphenylcarbazide based.
On a chem supplier catalog I've found that 1,5-Diphenylcarbazide can detect up to 0,000002 g/ml, which is 2000 ppb. But I know from a question on this website that the above reagent can detect up to 250 ppb.
And as per urine and blood concentrations we are looking at 10 ng/ml they detect.
So what is the threshold for 1,5-Diphenylcarbazide test and how they detect those minute amounts anyway?
Is there a DIY method of detecting something like 2 ppb at home?
P.S. I am talking about Hg2+ ions, if it is not clear