Topic
Retention time
Page 8 of 15 — Why retention time is a hint and not a fingerprint, and what co-elution can hide behind a beautiful single peak.
Messages — page 8 of 15
stable_not_volatileretention time is a hint#hplc-massspec · 2025-12-04hiccup_hollissingle wavelength detection can miss a co-eluting impurity that does not absorb there, your mileage will differ#coa-reading · 2025-12-07hiccup_hollisretention time shifts between runs are normal. relative retention time is the number to compare#coa-reading · 2025-12-07two_eight_cthats co-elution#hplc-massspec · 2025-12-08acetate_ashdoes retention time on its own tell you what the compound is#hplc-massspec · 2025-12-08pbs_pipbaseline drift on a gradient is normal. baseline drift on an isocratic hold is your column#hplc-massspec · 2025-12-08tail_factorunrelated but do you trust an area percent from a shallow gradient#hplc-massspec · 2025-12-11mg_per_mlwhats a normal gradient for a peptide this size#hplc-massspec · 2025-12-11mg_per_mlhow do you tell co-elution from a clean single peak two labs a point or two apart on the same lot is normal and gets mistaken…#hplc-massspec · 2025-12-11zoya_zeroshow do you tell co-elution from a clean single peak a certificate with a number and no chromatogram is asking you to trust the…#hplc-massspec · 2025-12-12assay_not_puritysingle wavelength detection can miss a co-eluting impurity that does not absorb there#coa-reading · 2025-12-13halifax_hplcsingle wavelength detection can miss a co-eluting impurity that does not absorb there#coa-reading · 2025-12-14underfill_umasingle wavelength detection can miss a co-eluting impurity that does not absorb there#coa-reading · 2025-12-16power_through_nohow do you tell co-elution from a clean single peak#hplc-massspec · 2025-12-17reading_the_pinsthe report says retention time matches the standard so it is confirmed as tirzepatide. that seems solid to me?#hplc-massspec · 2025-12-17void_volumeand RT drifts on its own anyway. new column, different lot of acetonitrile, column temperature two degrees out, pump seal…#hplc-massspec · 2025-12-17reading_the_pinsso how does anyone report RT usefully#hplc-massspec · 2025-12-17void_volumelike this#hplc-massspec · 2025-12-17igf_one_ivyretention time is a hint#hplc-massspec · 2025-12-18blank_runfollow up do you trust an area percent from a shallow gradient a certificate with a number and no chromatogram is asking you…#hplc-massspec · 2025-12-18a1c_lagthe retention time on this one is different from the last lot, problem#coa-reading · 2025-12-19a1c_lagretention time shifts between runs are normal. relative retention time is the number to compare#coa-reading · 2025-12-19gip_glp_gilthats co-elution#hplc-massspec · 2025-12-19vik_verifiesco-elution is the failure mode that a beautiful single peak is most likely to be hiding#hplc-massspec · 2025-12-19coa_or_coperetention time is a hint#hplc-massspec · 2025-12-19vat_on_importsingle wavelength detection can miss a co-eluting impurity that does not absorb there#coa-reading · 2026-01-03sharps_comedydoes retention time on its own tell you what the compound is#hplc-massspec · 2026-01-03sharps_comedywhats a normal gradient for a peptide this size#hplc-massspec · 2026-01-03tokyo_taperbaseline drift on a gradient is normal. baseline drift on an isocratic hold is your column#hplc-massspec · 2026-01-03sharps_comedyretention time is a hint#hplc-massspec · 2026-01-03sharps_comedyshallow gradient#hplc-massspec · 2026-01-03pinch_not_stretchrelative retention time against a standard is comparable between labs. absolute minutes are not#hplc-massspec · 2026-01-03blank_runthats co-elution#hplc-massspec · 2026-01-03travel_coolersingle wavelength detection can miss a co-eluting impurity that does not absorb there#coa-reading · 2026-01-04rotate_the_sitedoes retention time on its own tell you what the compound is#hplc-massspec · 2026-01-04void_volumeretention time is a hint#hplc-massspec · 2026-01-06area_percentwhats a normal gradient for a peptide this size#hplc-massspec · 2026-01-06marrow.moddo you trust an area percent from a shallow gradient#hplc-massspec · 2026-01-07low_and_slowretention time is a hint, not a fingerprint. two different peptides can co-elute perfectly happily#hplc-massspec · 2026-01-07tail_factorcoming back to this do you trust an area percent from a shallow gradient#hplc-massspec · 2026-01-09ghent_gradientsingle wavelength detection can miss a co-eluting impurity that does not absorb there#coa-reading · 2026-01-10cold_chain_cmdrrelative retention time against a standard is comparable between labs. absolute minutes are not#hplc-massspec · 2026-01-11cold_chain_cmdrretention time is a hint#hplc-massspec · 2026-01-11ferrous_ashshallow gradient#hplc-massspec · 2026-01-11freeze_thawretention time is a hint, not a fingerprint. two different peptides can co-elute perfectly happily#hplc-massspec · 2026-01-11relabel_watchthe retention time on this one is different from the last lot, problem#coa-reading · 2026-01-12deamidationright so co-elution is the failure mode that a beautiful single peak is most likely to be hiding#hplc-massspec · 2026-01-12eight_mmbaseline drift on a gradient is normal. baseline drift on an isocratic hold is your column, from memory#hplc-massspec · 2026-01-12HPLC_Hankretention time shifts between runs are normal. relative retention time is the number to compare, take that with a pinch of salt#coa-reading · 2026-01-13sharps_bin_sidretention time is a hint, not a fingerprint. two different peptides can co-elute perfectly happily#hplc-massspec · 2026-01-14sharps_bin_sidco-elution is the failure mode that a beautiful single peak is most likely to be hiding#hplc-massspec · 2026-01-14amylin_amybaseline drift on a gradient is normal. baseline drift on an isocratic hold is your column#hplc-massspec · 2026-01-16slow.taperretention time is a hint, not a fingerprint. two different peptides can co-elute perfectly happily#hplc-massspec · 2026-01-16slow.taperthats co-elution#hplc-massspec · 2026-01-16tail_factorretention time shifts between runs are normal. relative retention time is the number to compare#coa-reading · 2026-01-22void_volumeretention time shifts between runs are normal. relative retention time is the number to compare#coa-reading · 2026-01-23hk_hplcupdate on the earlier thing relative retention time against a standard is comparable between labs. absolute minutes are not#hplc-massspec · 2026-01-23never_for_salebaseline drift on a gradient is normal. baseline drift on an isocratic hold is your column#hplc-massspec · 2026-01-23warsaw_vialdo you trust an area percent from a shallow gradient#hplc-massspec · 2026-01-23never_for_salehow do you tell co-elution from a clean single peak#hplc-massspec · 2026-01-23