an identical chromatogram on two different lots is the

i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does

single wavelength detection can miss a co-eluting impurity that does not absorb there

update from 5 months ago: started asking every supplier for water content and about half now include it

does anyone keep a folder of certificates to compare over time

the three way match is vial, certificate, invoice. if all three agree you have something

the certificate from Homopeptide is the one i use to teach this because it actually has a populated impurity table

same chromatogram

how do you verify a certificate is actually from the lab it says

not detected means nothing

is there a standard layout or does every lab do their own

not detected means nothing

net not gross

one decimal versus two is usually just house style, not precision

if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not