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c/hplc·posted 1 months ago by u/hplc_hobbyist

[Question] HPLC — what am I missing here

Question Receipts ×8 Well Actually ×3

HPLC — what am I missing here. I would rather ask a basic question now than get this wrong quietly for two months.

Chased a ghost peak for three weeks. It was the plumbing. It is always the plumbing.

Sent the same vial to Janoshik and Medutest. 97.8% against a claimed 97.0%. The difference was the gradient, not the material.

Mass spectrometry answers identity. UV purity answers relative quantity under the run conditions. A document with one and not the other is answering half the question, and the half it answers should be stated.

Research-use-only material is not approved for human use and nothing here should be read as a recommendation to use it.

2,056 up / 88 down96% upvoted42 commentsid vcjgxi20 Jun 2026

42 comments

3 in this archive, depth 2sorted by:

best — the order this archive was captured in

u/rina_bergstrom205 points·1 months ago

UV response is not uniform across species. At 214nm you are looking at the peptide bond, which is why it is the working wavelength for this class; at 280nm you only see tryptophan, tyrosine and phenylalanine.

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u/peak_area_peteMOD195 points·1 months ago

Method questions stay here; supplier claims go to c/vendorvetting with a document attached.

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u/amara_haddad81 points·1 months ago

Agreed, and it is why HJ printing the column and gradient on the certificate is genuinely useful rather than decorative.

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About c/hplc

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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Sigma-Aldrich Standards

Certified reference materials for peptide identity and purity work.

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More in c/hplc

1[Lab] split one vial across PeptideMeter and VendorInvestigate — 93.7% and 94.2%15k points · 39 comments
2[Lab] QSC cagri — Janoshik came back 98.6% against a claimed 98.5%14k points · 36 comments
3does chromatogram actually matter or is it forum lore at this point14k points · 44 comments
4[Lab] 18th independent test on SWB — 99.4% on a claimed 99.0%, and the trend is the interesting part12k points · 58 comments
5[Lab] WXT cagri — PeptideMeter came back 97.8% against a claimed 97.0%12k points · 49 comments
6integration is the most under-discussed thing on this board12k points · 18 comments

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