two certificates from the same supplier have an identical chromatogram, is that normal
#coa-reading 2025-12-07
Sunday30 messages9 participantstimes are UTC
Highlights from this day
- VialBot — Reminder set. I will post here in 6 days. 20:21
- tail_factor — one decimal versus two is usually just house style, not precision 20:29
- hiccup_hollis — does anyone actually check the residual solvents section 20:58
- underfill_uma — a certificate should name the method, the instrument, the column and the operator. most name none of those, anyway 22:12
Channel stats, last 30 days: 113 messages from 25 members.
gross mass on a jewellery scale plus the water content is enough to catch most underfills
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Reminder set. I will post here in 6 days.
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one decimal versus two is usually just house style, not precision
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is water content normally on a certificate or do you have to ask
whats the related substances table actually telling me
purity is not assay
not detected means nothing
single wavelength detection can miss a co-eluting impurity that does not absorb there, your mileage will differ
does anyone actually check the residual solvents section
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mixed fonts and inconsistent kerning in one document is worth a second look
i asked KP for the method and they sent it. that alone put them ahead of most
sloppy not sinister
good certificate actually
is there a standard layout or does every lab do their own
i have never seen a research certificate with an endotoxin result on it. not once
not evidence on its own
retention time shifts between runs are normal. relative retention time is the number to compare
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration, someone check my working
the related substances table is the interesting part. a row of "not detected" means they did not look hard
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
what does net peptide content mean next to gross mass
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019, i have it written down somewhere
no lot number on this certificate, does that make it worthless
a certificate should name the method, the instrument, the column and the operator. most name none of those, anyway
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ok so the certificate from QSC is the one i use to teach this because it actually has a populated impurity table, n of 1 obviously
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if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
does purity by hplc at one wavelength miss things