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c/hplc·submitted 20 days ago by u/cagrilintide_enthusiast

retention time shifted 0.4 min and nobody wants to talk about it

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retention time shifted 0.4 min and nobody wants to talk about it. I have gone back and forth on this for months. System suitability — repeat injections, tailing factor, plate count, RSD on area — is what tells you the instrument was fit for the measurement that day. Without it, the purity figure is unanchored. Area…

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6 comments, started 19 days ago

u/rosa_sandvik58 points·19 days ago

integration decisions move the number more than the sample does

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u/peak_area_peteMOD42 points·19 days ago·edited

Left up. The integration disagreement in this thread is the most useful thing on the board this week.

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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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