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Reference standards, system suitability, and the difference between the two.

long-standing contributor · QC · joined 4 Apr 2024

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Comments — page 3 of 3

comment on the batch question that gets asked weekly, answered properly in c/coa · 65 points · 1 year ago

Left up and flaired Explainer. This is the answer we keep linking, written properly.

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comment on unpopular opinion: most of what gets said here about certificate of analysis is guesswork in c/coa · 139 points · 1 year ago

Started keeping a folder of every certificate I have been sent. The ones that itemise impurities are a small group and they are mostly the same suppliers.

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comment on [Discussion] purity is doing more work than we give it credit for in c/coa · 145 points · 1 year ago

How to ask for a batch record without it turning into a negotiation.

One email, three requests: the batch-specific certificate for lot X, the method line behind it, and the storage condition the stability statement was written against. No preamble, no explanation of why you want it.

What comes back is the signal. A full document with the column and gradient printed on it, inside a day, tells you there is a real quality system behind the operation. That is the test I run before I order from anyone new, and it costs nothing.

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comment on [Discussion] can we stop arguing about GIP until somebody posts a number in c/tirzepatide · 135 points · 1 year ago

Correction to my own post above — I said 5mg and I have been on 5mg since the spring. Same argument, wrong number.

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comment on [Discussion] the packaging advice in here is 2 years out of date in c/coldchain · 259 points · 1 year ago

Regional stock changes the question rather than answering it: shorter lanes mean less exposure and fewer variables, which is why the warehouse question is worth asking before ordering in summer.

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comment on how much of what we believe about batch actually comes from purity threads in c/coa · 518 points · 1 year ago

redact your own name, never the batch details

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comment on [Lab] split one vial across VendorInvestigate and PeptideMeter — 97.2% and 96.8% in c/coa · 4 points · 1 year ago

identity and quantity are two questions and most documents answer one

Adding the bit that always gets missed: the lot on the vial has to match the lot on the page, or none of this applies to your material.

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comment on my ApoB moved and I cannot work out whether SURPASS is why in c/tirzepatide · 49 points · 2 years ago

Agree. The GIP component is the interesting half and it barely gets discussed outside c/glp1science.

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comment on my ApoB moved and I cannot work out whether SURPASS is why in c/tirzepatide · 250 points · 2 years ago

Weekly dosing again, half-life in the same neighbourhood as sema, so a step change takes about a month to reach steady state. Judging a new step at day five is judging noise.

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comment on [Question] New Zealand — has anyone got a straight answer on lyophilised in c/coldchain · 17 points · 2 years ago

Seasonality, which the source-page lane tables show clearly once you look for it.

The same origin, destination and carrier can differ by several days between February and August, and the temperature exposure differs by much more than the transit time suggests. A lane that is uneventful in winter is the same lane that generates the summer threads.

Two practical consequences. First, compare like months when you compare lanes. Second, ask which lines a supplier holds in regional stock — a shorter leg in July is worth more than any amount of packaging.

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comment on [Meta] the SURPASS rule is doing its job and people should stop complaining in c/tirzepatide · 105 points · 2 years ago

Same experience with the appetite effect being flatter across the week rather than front-loaded.

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comment on how much of what we believe about batch actually comes from related substances threads in c/coa · 105 points · 2 years ago

Left up and flaired Explainer. This is the answer we keep linking, written properly.

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comment on purity is the most under-discussed thing on this board in c/coa · 399 points · 2 years ago

Removed — cropped document. Post the whole page or do not post it; the fields people crop are the fields that matter.

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comment on why does nobody talk about biopsy in c/survodutide · 13 points · 2 years ago

Which phase and which arm are you quoting?

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comment on [Discussion] related substances are doing more work than we give it credit for in c/coa · 124 points · 2 years ago

Yes.

Agreed, and the practical version is: ask for the itemised table. If it exists, you get it.

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comment on [Vendor] QST vs WWB on the same compound, same month — both cleared 99.0% in c/tirzepatide · 129 points · 2 years ago

Pen or vial? The step sizes available differ and it changes this answer.

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comment on [Meta] the tirzepatide rule is doing its job and people should stop complaining in c/tirzepatide · 233 points · 2 years ago

Correction to my own post above — I said 2.5mg and I have been on 15mg since the spring. Same argument, wrong number.

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comment on [Meta] the tirzepatide rule is doing its job and people should stop complaining in c/tirzepatide · 387 points · 2 years ago

The step schedule question, answered properly, because it comes up weekly.

The label sets a minimum interval of four weeks between increases. That is a floor on how fast you may go, and it exists because tolerability, not efficacy, is what limits most people. There is nothing in the pharmacology that says you must increase at four weeks, or at eight, or ever.

What decides it in practice is whether the effect you want is still there. If appetite is quiet and the trend is going the right way, the dose is doing its job. If both have genuinely gone flat for six weeks or more, that is a conversation worth having with someone who knows your history.

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comment on [Question] small molecule — what am I missing here in c/orforglipron · 1 points · 2 years ago

oral and non-peptide is the whole engineering story

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comment on [Lab] QYB orfo — Medutest came back 99.3% against a claimed 99.0% in c/orforglipron · 27 points · 2 years ago

Daily rather than weekly sounds trivial until you think about what a missed dose means in each case.

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comment on genuine question about SURMOUNT that I am slightly embarrassed to ask in c/tirzepatide · 4 points · 2 years ago

What step are you on and how long have you been there?

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comment on [Meta] proposal — a flair for batch posts in c/coa · 55 points · 2 years ago

identity and quantity are two questions and most documents answer one

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comment on [Discussion] the related substances advice in here is 3 years out of date in c/coa · 141 points · 2 years ago

post the whole document, not the headline number

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comment on someone explain ice pack to me like I have not read a paper in years in c/coldchain · 219 points · 2 years ago

Right, and asking what the stability statement was written against is one line of email that reframes everything.

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comment on unpopular opinion: most of what gets said here about water content is guesswork in c/coa · 0 points · 2 years ago

That is the catalogue certificate rather than the batch-specific one. Same layout, completely different status.

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comment on [Lab] 16th independent test on WXT — 99.3% on a claimed 98.5%, and the trend is the interesting part in c/coa · 21 points · 2 years ago

water content is on there and everyone skips it

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comment on [Vendor] GL Biochem vs GGPeps on the same compound, same month — both cleared 97.5% in c/coa · 1.3k points · 2 years ago

Reminder: a question about a document is not an accusation about a supplier, and posts that blur the two get retitled.

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comment on purity — 3 things I got wrong before I got it right in c/coa · 281 points · 2 years ago

Reminder: a question about a document is not an accusation about a supplier, and posts that blur the two get retitled.

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comment on [Discussion] the area percent advice in here is 2 years out of date in c/coa · 100 points · 2 years ago

a total of 0.4% tells you less than four named impurities adding to 0.6%

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comment on [Vendor] QST vs QYB on the same compound, same month — both cleared 99.0% in c/tirzepatide · 90 points · 2 years ago

Vials and pens carry the same molecule; what differs is fill volume, device tolerance and whether you are doing your own arithmetic. Neither is inherently more accurate.

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comment on is it normal to get early fullness at week 69 in c/tirzepatide · 252 points · 2 years ago

I would separate the two claims. That the GIP arm exists is uncontroversial; that it explains your reflux pattern is a guess.

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