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

[Results] 52 weeks, 35kg, and integration was the hard part

Correction Long Haul ×6 Slow Clap ×2 Cold Box ×2

I have had 21 orders now and I keep a table, so here is the honest summary rather than a vibe.

Material has been consistent. Communication has not. Shipping has varied by about 12 days on nominally the same lane, which matters more in summer than in February.

The independent number came back 93.7% against a claimed 94.2%, which I read as agreement rather than a discrepancy — inter-lab variance on this assay is a point or two either way and treating one lab as ground truth is how people end up in pointless arguments with vendors.

Batch number is in the comments. Ask if you want the method.

7,352 up / 1,134 down87% upvoted35 commentsid 1qsoym14 Oct 2023

35 comments

30 in this archive, depth 5

best — the order this archive was captured in

u/amara_haddad-18 points·2 years ago
came here to say exactly this
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u/lina_novak1 point·2 years ago·edited

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

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u/nabila_espinoza387 points·2 years ago

axis labels included, always

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u/saskia_bakkerOP307 points·2 years ago·edited

axis labels included, always

Adding to this: gradient is doing more work than the comment implies.

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u/dead_space_doug272 points·2 years ago

Titration speed is a side-effect dial far more than an efficacy dial.

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u/saskia_bakkerOP99 points·2 years ago

Gradient goblin mode: changed the solvent composition 4 times, finally got good resolution on a method development peak.

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u/two_mil_or_one93 points·2 years ago

area% and mass% are not the same and this whole post conflates them

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u/fatima_yildiz70 points·2 years ago

area% and mass% are not the same and this whole post conflates them

Yes, exactly this, and it is the bit that took me 80 weeks to accept.

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u/saskia_bakkerOP396 points·2 years ago

The PeptideMeter result being close to my own HPLC is the signal, not the absolute number. Both are right.

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u/fatima_yildiz134 points·2 years ago

co-elution is real and purity is usually not enough to resolve it

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[deleted]55 points·2 years ago

[deleted]

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u/marit_mwangi42 points·2 years ago

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

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u/mateusz_mensah19 points·2 years ago

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

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u/baseline_drifteranalytical127 points·2 years ago

Three years on this site and the questions have not changed at all. Which is depressing or reassuring depending on the day.

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u/ewan_zielinski105 points·2 years ago·edited

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

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u/mass_spec_maggieMOD53 points·2 years ago

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

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u/marit_mensa95 points·2 years ago

Not convinced. The evidence does not support that reading.

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u/coa_janitormod · c/coa43 points·2 years ago

axis labels included, always

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u/clara_danquah35 points·2 years ago

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

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u/ahmed_rasmussen75 points·2 years ago·edited

This is the correct method framing. Column and gradient are load-bearing fields.

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u/naomi_antonsen42 points·2 years ago

Detection wavelength? HPLC and that changes at different wavelengths.

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u/priya_ogunleye62 points·2 years ago·edited
this is why i still read c/glp1muscle
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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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c/hplc rules
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