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

switched from 2.4mg to 1.7mg and the early fullness got better, not worse

Discussion Receipts ×7 Sourced ×2 Cold Box ×2

Something I noticed reading old threads that I have not seen said out loud.

The advice on gradient in this community changed substantially around the start of last year, and nobody went back and updated the older posts. So depending on which thread the search engine hands you, you get two contradictory answers with the same confidence.

I have listed what I think the current consensus is below. Correct me — that is the point of posting it.

6,585 up / 1,169 down85% upvoted21 commentsid 1r2okb29 Oct 2023

21 comments

11 in this archive, depth 3

best — the order this archive was captured in

u/hplc_hobbyistMOD712 points·2 years ago

Tracking number removed. It identifies both ends of a shipment.

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u/liv_okafor173 points·2 years ago

Strongly agree. Largest single impurity tells a different story than total purity.

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u/step_count_stan657 points·2 years ago

Strongly agree. Largest single impurity tells a different story than total purity.

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u/dizzy_on_standing290 points·2 years ago·edited

Disagree. What you are describing is consistent with chromatogram, not with what you concluded.

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u/andres_restrepo134 points·2 years ago·edited

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

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[removed]314 points·2 years ago

[removed by moderator]

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u/ravi_bergstrom237 points·2 years ago·edited

Did they post the raw trace or just the summary?

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u/mariam_cabrera406 points·2 years ago

Strongly agree. Largest single impurity tells a different story than total purity.

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u/crosspost_bot_no227 points·2 years ago

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

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u/insulin_syringe_ian211 points·2 years ago·edited

Not convinced. The evidence does not support that reading.

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u/canada_coverage311 points·2 years ago·edited

A shoulder on the main peak that 18 analysts integrated 40 different ways. Same trace, 98.0 spread.

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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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