c/hplc wiki

What this community is for

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.

c/hplc was created on 14 Sep 2023 and currently has 31,700 members and 130 captured submissions. It sits in the busiest tier of the site, which mostly affects how fast a question gets answered rather than how well.

Rules, and why each exists

Community rules come first, then the six site-wide rules that apply everywhere on GLP Research Hub. Community rules are enforced by the moderators listed at the bottom of this page; site rules are enforced by everyone.

1. Chromatogram or it did not happen. Axis labels included.
2. State the method: column, gradient, detection wavelength, injection volume.
3. Area% is not mass%. Posts that conflate them get a correction flair, not a removal.

And the site rules, which are short on purpose:

1. Independent community. Nobody here sells anything, and anyone who tries is banned.
2. Not medical advice. Describe what you did; never prescribe to a stranger.
3. Claims need evidence. Batch numbers, dated screenshots, independent test reports, or a citation.
4. No referral links, discount codes or affiliate URLs. Permanent ban, no appeal.
5. No contact handles, wallet addresses or tracking numbers — they identify people.
6. Be recognisably decent. Disagree hard, insult nobody.

Terms you will see

Vocabulary that turns up constantly in c/hplc. Each links to the topic page, which collects every submission that touches it.

• HPLC — high-performance liquid chromatography — the workhorse separation method here.
• chromatogram — the raw detector trace. Post it; the summary line hides the interesting parts.
• gradient — the changing mobile-phase composition that separates the peaks.
• LC-MS — chromatography plus mass spectrometry; the method that answers identity.
• integration — deciding where each peak starts and stops — where a lot of the number comes from.
• purity — usually area% from a UV chromatogram: how much of what the detector saw was product.
• method development — building a separation that resolves what you care about.

Start here

The twelve highest-scoring submissions in this community. Not necessarily the most correct — the most agreed-with, which is a different thing, and worth remembering when you read them.

1. [Lab] split one vial across PeptideMeter and VendorInvestigate — 93.7% and 94.2% — 15k points, 39 comments, 2 years ago
2. [Lab] QSC cagri — Janoshik came back 98.6% against a claimed 98.5% — 14k points, 36 comments, 2 years ago
3. does chromatogram actually matter or is it forum lore at this point — 14k points, 44 comments, 2 years ago
4. [Lab] 18th independent test on SWB — 99.4% on a claimed 99.0%, and the trend is the interesting part — 12k points, 58 comments, 2 years ago
5. [Lab] WXT cagri — PeptideMeter came back 97.8% against a claimed 97.0% — 12k points, 49 comments, 1 year ago
6. integration is the most under-discussed thing on this board — 12k points, 18 comments, 2 years ago
7. [Lab] MKM cagri — Medutest came back 97.2% against a claimed 97.0% — 11k points, 64 comments, 1 year ago
8. help me understand method development, I have read the wiki twice — 10k points, 46 comments, 2 years ago
9. [Question] how do you actually verify gradient — 9.5k points, 14 comments, 2 years ago
10. [Question] is 94.2% actually fine or am I being sold a rounding error — 8.8k points, 31 comments, 2 years ago
11. [Lab] split one vial across PeptideMeter and VendorInvestigate — 96.8% and 99.1% — 8.6k points, 48 comments, 1 year ago
12. [Lab] ERP cagri — PeptideMeter came back 98.8% against a claimed 98.0% — 8.4k points, 28 comments, 2 years ago

Asked constantly

• two labs, same vial, 98.1 and 96.4. both right?
• peak at 4.2 min, nobody can tell me what it is, ideas
• two labs, same vial, 98.1 and 96.4. both right?
• [Question] what is a reasonable system suitability RSD for this work
• reading integration threads from 2024 and half of it aged badly
• [Question] HPLC — what am I missing here
• genuine question about purity that I am slightly embarrassed to ask
• [PSA] HPLC is not what most of this community thinks it is
• [PSA] chromatogram is not what most of this community thinks it is
• [Question] how do you actually verify LC-MS

If your question is on that list, read the answers there first. If it is not, ask it — that is what the community is for, and "this has been asked" is only a helpful reply when it comes with a link.

Who runs this

Moderation here is done by volunteers who also post as normal members. They are not clinicians, not vendors, and not paid.

• u/sig_figs_sam — c/hplc mod. Analytical chemist by trade. Round your numbers responsibly.
• u/hplc_hobbyist — Bought a second-hand HPLC and a lifetime of regret. I post chromatograms, not conclusions.
• u/peak_area_pete — Area% is not mass%. I will keep saying this until the sun goes out.
• u/mass_spec_maggie — LC-MS/MS is my day job. Peptide mapping is my hobby. Both are the same job.