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ForumsCOA & Analytical TestingInter-lab variability in peptide testing — July 2024 Page 5

Inter-lab variability in peptide testing — July 2024

Dr.GastroMayo Fri, Sep 19, 2025 at 1:04 AM 41 replies 1,493 viewsPage 5 of 9
TirzTom
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Oct 12, 2025 at 9:56 AM#21
jennifer_SEA said:
COA red flags for certificates of analysis — here's what to look for when reviewing a Certificate of Analysis: No HPLC data: If there's no…

Same pattern here, and in the same order. Posting only so the count is not one.

Last edited: Oct 12, 2025 at 1:56 PM
11 11josh_phd_bmore, roxy_nash, tony_orlando and 8 others
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pat_auckland
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Oct 20, 2025 at 12:32 AM#22
jennifer_SEA said:
COA red flags for certificates of analysis — here's what to look for when reviewing a Certificate of Analysis: No HPLC data: If there's no…

My vendor review relevant to certificates of analysis: ordered 3 times from my current compounder. Consistency has been excellent.

Shipping: Next-day with cold pack
Packaging: Professional, discreet, proper labeling with lot/batch numbers
Purity: 99.4% average across orders (Janoshik verified)
Customer service: Responsive within 2 hours
Price: $132/month for semaglutide 1.7mg equivalent

10 10wanda_boise, NurseAsh_DET, BenResearch_OR and 7 others
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Dr.PeteFamMed
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Oct 27, 2025 at 3:03 PM#23

One concrete data point for the thread. The boring version of this is the one that works, and the boring version is: measure a baseline, change one variable, wait, measure again under the same conditions. Nobody wants that answer and it is still the answer.

9 9LindaRN_retired, tommy_boulder, hyun_seoul and 6 others
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Sigma-Aldrich — Research-Grade Standards

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wei_SG
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Nov 4, 2025 at 5:30 AM#24

A narrower follow-up, since the general answer is now clear:

What did you change at the same time, and can you separate the two now?

8 8RetaRick_CA, JenPlateau, SallyK_inj and 5 others
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VendorMark
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Nov 11, 2025 at 7:52 PM#25
Dr.PeteFamMed said:
The boring version of this is the one that works, and the boring version is: measure a baseline, change one variable, wait, measure again under the…

Pushing back on Dr.PeteFamMed here. Pushing back on the anecdote-stacking. Twenty people reporting the same thing is twenty samples from the same self-selected pool, not twenty independent confirmations.

Last edited: Nov 11, 2025 at 9:52 PM
7 7claudia_zurich, nancy_portland, rick_sfbay and 4 others
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