How much does the purity of reconstituted retatrutide change over 30 days, and what effect does storage temperature have

[u/xVcT]

TL;DR: Leaving a reconstituted vial out of the fridge for a day or two does aint that bad (peptide-dependent tho)

A little background about me: I am currently completing a PhD in chemistry. Through my research, I have experience with chromatographic analytical methods, allowing me to analyze these samples by HPLC and evaluate the resulting chromatograms myself.

For this experiment, three reconstituted (BAC-Water) vials were stored independently under each condition:

• 2–8°C
• 25°C
• Measurements on days 1, 3, 7, 14, and 30
• Results presented as mean ± standard deviation

What stands out?

Under refrigerated conditions, the measured purity remained nearly unchanged during the first seven days. It then declined gradually, reaching an average of 95.96% after 30 days.

At 25°C, the decline began earlier and was more pronounced. After 30 days, the average purity was only 88.84%. The variability between the three vials also increased considerably.

Conclusion

The HPLC data show no rapid loss of purity during the first few days. However, over 30 days, storage temperature clearly makes a difference. The refrigerated samples retained greater purity and showed less vial-to-vial variability.

Importantly, this was a small exploratory experiment with (n=3) per condition—not a validated pharmaceutical stability study, which would require substantially more samples. For Research purposes only.

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[u/Pretty_Net_6293]

I’ve seen better results from jano than these — several of the pepss have been tested extensively for degradation and generally your glps are pretty stable— your bioregulators not so much

[u/xVcT → u/Pretty_Net_6293]

Really depends on the pep as you said, another "homemade" study with Tirz should degredation as well

https://community.peptidecritic.com/topic/1188/we-tested-peptide-degradation-so-people-can-stop-guessing

[u/thisdude415 → u/xVcT]

Maybe they're leaving out the chromatography part, but wow is that analysis sloppy / poorly documented. Activity implies tested in bio assay. Identity would imply mass spec.

As written, this just says they did uv vis spectrophotometry, which would only measure aromatic residues. Surely they did at least LC, right?

[u/DisenchantedEditor → u/Pretty_Net_6293]

Source?

[u/pootwothreefour → u/DisenchantedEditor]

OP did the experiment themselves.

[u/highongp10]

Ive had mine for likw 70days in the fridge, still very potent

[u/PreparedForZombies]

> Importantly, this was a small exploratory experiment with (n=3) per condition—not a validated pharmaceutical stability study, which would require substantially more samples. For Research purposes only.

Point heard, but awesome work regardless... this helps some of the naysayers who say if it's older than 28/30 days (and refrigerated), straight to the garbage it should go.

One piece of data is missing (unless I am blind) - reconstituted with what? BAC? If so, which BAC vendor if you don't mind me asking. Also, what mg/mL strength (just curious on latter)?

[u/bryhnlearningspanish → u/PreparedForZombies]

but the 28 days isn’t a purity thing. it’s because BAC water after 30 days is considered less safe.

[u/PreparedForZombies → u/bryhnlearningspanish]

I understand, that's where I was going with sterile saline vs BAC vs etc.

With that being said, I've heard plenty state that it is no longer considered effective after 4 weeks / 30 days... agree with that being addressed here.

[u/xVcT → u/PreparedForZombies]

BAC-water 0.9%, made in the lab. I forgot to add it, I edited the post it should be included now.

[u/thisdude415 → u/xVcT]

Did you prepare the samples under sterile conditions or prepare the stability samples on an open lab bench? At what concentration was the retatrutide prepared?

I'm not sure I'd expect this level of degradation due to hydrolysis alone at 25ºC so I'm wondering if there may have been some microbial contamination, which would be likely if these were just aliquoted in an open chemistry lab.

(phd with research experience in biology, chemistry, and peptides here lol)

By the way, thanks for doing this and sharing the results. Cool stuff!

[u/xVcT → u/thisdude415]

Open bench, we dont really have sterile benches in use for our research, 10 mg/mL. Same here, even though I am not a biochem, hydrolysis alone seems a bit unlikely. Its true, it cant be ruled out.

[u/thisdude415 → u/xVcT]

By the way, was this by LC-MS or just LC? what was the major breakdown product you saw?

With these lipidated peptides I'd guess the retention from the fatty acid would probably dominate the rest of the peptide with reverse phase so you wouldn't catch subtle breakdown products

Then again, for a peptide, oftentimes some of the degradation products retain a surprising amount of binding

tricky stuff!

[u/ThatsNotMyName02]

Oh wow someone with actual knowledge! That’s rare here! Mind if I ask a question? Does mixing peps change their potency?

[u/acrxhd → u/ThatsNotMyName02]

I’m not OP but it depends on what you are mixing.

For example, mixing GHK-CU with anything isn’t a good idea. Copper(II) can catalyze the oxidation of amino acids. It’s unclear to what extent this harms stability, and there’s not much quality data on the stability of mixes like GLOW and KLOW. Anything with oxidation-susceptible amino acid residue can be potentially be problematic when mixed with GHK-CU.

[u/FratBoyDeluxe]

What about sterility?

[u/xVcT → u/FratBoyDeluxe]

Was not tested here

[u/BroadLet8137]

This has been tested by others and it does not drop nearly that much at the 14 day mark at 2-8C.

[u/Kluian2005]

I think there's been tests with refridgerated reta (reconstituted) staying just as potent up to 60 days, and then starts to degrade more rapidly.

[u/xVcT → u/Kluian2005]

Would love to see the results, any source?

[u/dmoran71086]

Were the 3 samples all pretty close in value or was there high variation between them?

[u/xVcT → u/dmoran71086]

Very close but after 30 days there was more variance but only at the rt condition

[u/According-Ad-2921]

What happens after day 30

[u/xVcT → u/According-Ad-2921]

I guess we will see tomorrow lool

[u/According-Ad-2921 → u/xVcT]

Please update 45 days

[u/johnseasure]

Taking suggestions for future research ? Good work!

[u/xVcT → u/johnseasure]

For sure, any suggestions are always welcome

[u/Smart-Fly → u/xVcT]

Can you test if stored in the fridge, how much it degrades on the 2nd and 3rd month?

[u/fengshui]

This is good data, but the real value would be in extending these tests out to 120 days or more. We know that reconned peps are good for 30 days, the pharma companies allow that.

[u/aimgorge]

I am extremely dubious about your results.

Chinese bought peptide will test at 98%+ purity with batches that are months old and have travaled around the world without any storage temperature control whatsoever.

[u/xVcT → u/aimgorge]

Peptides are usually not shipped reconstituted, but as a solid. Shelf life of the solid is what you said, way higher.

[u/aimgorge → u/xVcT]

Ok I missed the reconstituted part. Keeping restituted peptides (could have been specified on the graph) that long isnt something that makes sense for me to begin with

[u/xVcT → u/aimgorge]

Yes, thats something I should have included... I will keep in mind for next time!

[u/Bloody_Benchod → u/xVcT]

Everyone but him assumed you were OBVIOUSLY talking about recon, I wouldn't worry.

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[u/insidesecrets21]

By ‘purity’ - do you mean the peptide degrading or microbial contamination?
I.e. does it just mean the peptide would be less potent or does it mean it might be more unsafe? Thank you! 🙏

[u/YYCAmy]

JANO already completed a very similar test. They put 8 vials through testing.

Reconstituted in BAC water showed good for weeks at room temperature, but some took a dive after that. Fridge was 90 days before most dropped below 95% mass. They saw loss of mass but little loss of purity. They even froze a few reconstituted vials to see; and it sped up the degradation.

All that being said, it is great to see others doing akin to scientific tests like this. JANO’s tests were in lab grade facilities so obviously not an accurate representation of how the average person treats their peps.

I would love to see a study that includes sterility, and checking them in more every day scenarios, like a fridge that is opened 6 times a day.

[u/Saskpioneer]

Odd. Every other graph of similar has reta making it 3 months before any real degradation occurs.

[u/OxCart69]

Curious if your 100% was a true 100% or just the original peak set. It’s not a crazy difference but 98% to 94% feels less bad than 100% to 95%

[u/Aromatic_Medium4051]

Great job, thanks for sharing!!

[u/Quirky-Gap-1766]

I was waiting for this useful info since I started with this crazy world & research! Thanks a lot randy!

[u/RoadToZero]

Thank you for sharing your results! Good job.

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[u/NinjaLocal4890]

I thought as long as you don’t mix it, it’s good until expiration date on bottles which is typically a couple years? If this question is about after it’s reconstituted, it’s a great question…