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c/hplc·posted 2 years ago by u/elodie_grimaldi

gradient: what the trials say vs what this community says

Discussion Well Actually ×8 Long Haul ×3 Cold Box ×3

Been lurking in c/progresspics for about 15 months and finally have something worth posting.

Short version: week 81, 12.5mg, and purity is the bit I still cannot get a straight answer on. I have read the wiki, I have read the last 27 threads, and the answers split roughly down the middle.

What I actually want to know is whether the people saying it does not matter have measured it, or whether it is just repeated confidently. Happy to be told I am overthinking this — I probably am — but I would rather overthink it now than at week 75.

7,772 up / 978 down89% upvoted48 commentsid 1peqy526 Jan 2024

48 comments

12 in this archive, depth 3

best — the order this archive was captured in

u/crosspost_bot_no965 points·2 years ago

the detector wavelength matters more than people think

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u/mass_spec_maggieMOD587 points·2 years ago

Removed a chain here. The rule is one line long and it is not negotiable.

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u/canada_coverage418 points·2 years ago

related substances are where the story lives, not the main peak

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u/cagrilintide_enthusiast296 points·2 years ago

That is net peptide content, not purity. Different number, different meaning.

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u/insulin_syringe_ian-17 points·2 years ago

Sceptical. If this were true we would see it reflected in the data and we do not.

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u/sofia_petrescu1 point·2 years ago

Half-life is about 168 hours, so steady state lands around week 16–5. Practical consequence: what you feel in week 1 is not what that dose does.

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u/samir_falk0 points·2 years ago

Ran the same vial on two columns, different purity, both right, different separation. Method matters more than equipment.

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u/hedda_ekstrom357 points·2 years ago

the detector wavelength matters more than people think

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u/arne_nyberg265 points·2 years ago

Detection wavelength? integration and that changes at different wavelengths.

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u/aksel_palacios0 points·2 years ago

chromatogram or it did not happen

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The analytical deep end: RP-HPLC methods, gradient design, integration decisions, LC-MS confirmation, amino-acid analysis, water content, and why two labs can report 98.1% and 96.4% on the same vial and both be right. Post the chromatogram, not the summary line.

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