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c/hplc·posted 4 months ago by u/blunt_coldbox_2024

three years of integration threads, summarised so you do not have to read them

Question Receipts ×2 Well Actually ×3

Been lurking in c/progresspics for about 17 months and finally have something worth posting.

Short version: week 39, 12.5mg, and chromatogram is the bit I still cannot get a straight answer on. I have read the wiki, I have read the last 23 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 33.

2,684 up / 425 down86% upvoted35 commentsid 1v5n4e18 Mar 2026

35 comments

23 in this archive, depth 4

best — the order this archive was captured in

u/rina_bergstrom268 points·4 months ago·edited

The related substances profile is way more interesting than the main peak %. A 98% with 13 peaks is different from a 98% that is one 25% impurity.

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u/mateusz_mensah115 points·4 months ago

Disagree but this is the good kind of wrong — it is specific enough to be checked.

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u/careful_gradient231 points·4 months ago

I am going to push back on this slightly.

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u/sig_figs_samMOD126 points·4 months ago

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

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u/hugo_bergstrom67 points·4 months ago

a round-robin on baseline integration would be genuinely useful

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u/dilara_nyberg103 points·4 months ago

Detection wavelength? method development and that changes at different wavelengths.

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u/blunt_coldbox_2024OP62 points·4 months ago

Gradient goblin mode: changed the solvent composition 18 times, finally got good resolution on a integration peak.

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u/rania_okonkwo186 points·4 months ago
post the spreadsheet
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u/blunt_coldbox_2024OP-21 points·4 months ago

state the method: column, gradient, detection wavelength, injection volume

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u/andres_restrepo78 points·4 months ago

The evidence standard in c/vendorvetting gets called too strict about once a month, and every time, the thread ends with the complainant agreeing.

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u/blunt_coldbox_2024OP49 points·4 months ago

two labs, two different baselines, two different purity numbers, both honest

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u/b12_baseline72 points·4 months ago

a round-robin on baseline integration would be genuinely useful

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u/hydration_hank52 points·4 months ago

Yeah, the chromatogram profile matters more than the headline number.

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u/aksel_palacios43 points·4 months ago

The related substances profile is way more interesting than the main peak %. A 98% with 7 peaks is different from a 98% that is one 16% impurity.

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u/naomi_antonsen12 points·4 months ago

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

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u/hugo_bergstrom14 points·4 months ago

a round-robin on baseline integration would be genuinely useful

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u/ravi_bergstrom5 points·4 months ago

instrument quality is less important than analyst consistency

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u/nnt_nate12 points·4 months ago

I am going to push back on this slightly.

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u/ewan_marchand38 points·4 months ago

Rodent data is rodent data. Dose scaling is not linear and the models tell you what to investigate, not what to expect.

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u/rina_nascimento26 points·4 months ago

Small correction: the trial was 9 weeks, not 7. Does not change your point but people will quote it.

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u/lina_novak20 points·4 months ago·edited

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

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u/yara_boateng11 points·4 months ago

the gradient is doing the separation work, not the column alone

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u/marisol_frisk19 points·4 months ago

Not to be pedantic but chromatogram and HPLC are being used interchangeably and they are not interchangeable in real life.

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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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