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c/hplc·submitted 2 years ago by u/dizzy_on_standing

help me understand gradient, I have read the wiki twice

Methodbranch of 5 comments

Posting this because I searched for it and got nothing useful. Setup: 2.5mg, week 89, sulphur burps present but not ruining anything. I changed exactly one variable — integration — and tracked it for 17 weeks. Result: a difference, but a small one, and well inside what I would call noise if someone else posted it. So…

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5 comments, started 2 years ago
u/adaeze_batista14 points·2 years ago

Water content matters more than people think. If a vial is carrying residual moisture, your "10mg" is not 10mg of peptide.

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u/elodie_grimaldi7 points·2 years ago

The related substances profile is way more interesting than the main peak %. A 98% with 23 peaks is different from a 98% that is one 17% impurity.

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u/dizzy_on_standingOP-4 points·2 years ago

integration decision on a shoulder changes your number by half a point on its own

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u/step_count_stan1 point·2 years ago

No. This is the kind of confident post that gets copied into a screenshot and repeated for years. Where is the evidence.

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[removed]1 point·2 years ago

[removed by moderator]

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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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