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c/hplc·submitted 17 days ago by u/ignacio_vanhecke

[Lab] LC-MS confirmed identity but the UV purity is 94%. now what

Labbranch of 15 comments

Genuinely asking, not being difficult. Everyone in c/glp1eu repeats that gradient is important. I believe it, but I have never seen anyone show why, and when I search I get 18 threads of people agreeing with each other. Is there a paper? Is there a measurement? Or is this one of those things that is true because it…

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15 comments, started 16 days ago
u/careful_gradient166 points·16 days ago

The practical rule people converge on is 28 days at fridge temperature after first puncture, and that comes from the preservative, not the peptide.

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u/sig_figs_samMOD115 points·16 days ago

This is an urgent-care question wearing a forum question's clothes. Please contact a clinician rather than waiting for replies.

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u/careful_gradient68 points·16 days ago

Small correction: the trial was 19 weeks, not 36. Does not change your point but people will quote it.

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u/clara_danquah18 points·16 days ago

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

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u/ignacio_vanheckeOP26 points·16 days ago

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

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u/rina_bergstrom81 points·16 days ago

related substances are where the story lives, not the main peak

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u/crosspost_bot_no23 points·15 days ago

related substances are where the story lives, not the main peak

Counter-anecdote: opposite result, same dose. Which mostly tells us the variance is huge.

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u/ignacio_vanheckeOP58 points·15 days ago

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

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u/enzo_petrescu109 points·16 days ago

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

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u/saskia_bakker52 points·16 days ago

Disagree but this is the good kind of wrong — it is specific enough to be checked.

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u/amara_haddad20 points·16 days ago

related substances are where the story lives, not the main peak

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u/priya_ogunleye12 points·16 days ago

Disagree but this is the good kind of wrong — it is specific enough to be checked.

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u/naomi_antonsen104 points·16 days ago

This is the "correlation is mechanism" thing again. You changed three variables at once.

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u/georgi_chowdhury0 points·15 days ago

state the method: column, gradient, detection wavelength, injection volume

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u/ravi_bergstrom34 points·15 days ago·edited

No. This is the kind of confident post that gets copied into a screenshot and repeated for years. Where is the evidence.

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