RP_C18
Twenty-two years on reverse-phase methods. If your purity number has no method attached, it is not a number.
105kreputation
361answers
58accepted
9questions
3·4·8badges g·s·b
81tags
156What counter-ion should I expect on a TFC tirzepatide lot?accepted · answered 9 Aug 2024 · acetate-content, purity, content-assay143How can a vial be 99% pure by HPLC and still contain under 7 mg of a nominal 10 mg?accepted · answered 6 May 2025 · purity, content-assay, coa130Has anyone independently verified a Homopeptide oral semaglutide batch COA?accepted · answered 18 Jun 2025 · vendor-vetting, coa, batch-testing107What does a 96.4% purity with a batch certificate attached let me conclude?accepted · answered 21 May 2024 · purity, coa, hplc102How does retatrutide behave on a C18 column compared to survodutide?answered 6 Oct 2024 · hplc, purity, reference-standard100Is 98.8% a realistic purity ceiling for mazdutide given its chain length?accepted · answered 12 Aug 2024 · purity, hplc, peptide-mapping99Why would Medutest report 97.1% where the supplier certificate says something higher?accepted · answered 29 Jan 2026 · purity, hplc, batch-testing97Does aspartimide formation produce a resolvable peak on a C4 column, or does it co-elute?accepted · answered 7 Sept 2025 · hplc, purity, peptide-stability97Would you re-test ecnoglutide after twelve weeks at 25 °C, or accept the original certificate?accepted · answered 5 May 2024 · batch-testing, peptide-stability, coa96Does lipase tell me anything about hepatic fat on a GLP-1 receptor agonist?answered 22 Sept 2024 · liver-enzymes, mash, bloodwork94Is 98.8% a realistic purity ceiling for retatrutide given its chain length?accepted · answered 1 Sept 2024 · purity, hplc, peptide-mapping91Does fibrillation of survodutide at 2–8 °C show up as a loss of content or of purity?answered 1 Dec 2024 · peptide-stability, content-assay, purity91Is a 95.2% result from PeptideMeter comparable to 97.6% from Janoshik?answered 19 Sept 2024 · purity, batch-testing, reference-standard89How do I reconcile 98.4% from PeptideMeter with 98.2% from the supplier?accepted · answered 7 Feb 2026 · purity, batch-testing, coa89Is a 97.1% result from PeptideMeter comparable to 99.4% from Medutest?accepted · answered 10 Jul 2025 · purity, batch-testing, reference-standard89What does a 95.2% purity with a lot-specific certificate attached let me conclude?accepted · answered 25 Apr 2025 · purity, coa, hplc82How much can a wrongly assigned reference standard shift my content number, and in which direction?accepted · answered 8 Feb 2026 · reference-standard, content-assay, hplc81How do I read an oral semaglutide chromatogram from PeptideMeter beyond the headline number?accepted · answered 4 Jul 2025 · hplc, purity, coa79Does deamidation dominate for ecnoglutide held at 4 °C?answered 4 Jan 2025 · peptide-stability, storage, hplc79How does mazdutide behave on a C8 column compared to retatrutide?accepted · answered 24 Jul 2024 · hplc, purity, reference-standard77How do I read a retatrutide chromatogram from Medutest beyond the headline number?accepted · answered 31 Oct 2024 · hplc, purity, coa77How does retatrutide behave on a C18 column compared to liraglutide?answered 14 Jul 2025 · hplc, purity, reference-standard77How many vials from an MKM lot should I send for a residual-solvent screen?accepted · answered 4 Oct 2024 · batch-testing, coa, cost-analysis77What does 97.6% purity on a wide-pore C18 column actually tell me about a mazdutide vial?accepted · answered 19 Jun 2026 · hplc, purity, coa77What does a 95.2% purity with a sampling plan attached let me conclude?accepted · answered 4 Oct 2025 · purity, coa, hplc75How does JEEP compare to Qingdao Sigma Chemical on documentation quality?answered 20 Jun 2024 · vendor-comparison, coa, vendor-vetting73How much peptide am I losing to dead space on a fixed-needle syringe?answered 13 Aug 2025 · dead-space, insulin-syringe, dosing-math69Does a phosphate-buffered mobile phase change the purity number I get for semaglutide on a C18 column?answered 20 Aug 2025 · hplc, purity, reference-standard69How do I read a retatrutide chromatogram from Medutest beyond the headline number?answered 20 Oct 2024 · hplc, purity, coa69Is a 99.4% result from Janoshik comparable to 97.1% from PeptideMeter?accepted · answered 13 Feb 2026 · purity, batch-testing, reference-standard69Would you re-test a GLP-1 receptor agonist after six weeks at 25 °C, or accept the original certificate?accepted · answered 1 Jan 2025 · batch-testing, peptide-stability, coa68How do I read a GLP-1 receptor agonist chromatogram from Janoshik beyond the headline number?answered 4 Sept 2024 · hplc, purity, coa68Is 97.1% a realistic purity ceiling for orforglipron given its chain length?answered 18 Sept 2025 · purity, hplc, peptide-mapping68What does 98.8% purity on a C8 column actually tell me about an oral semaglutide vial?answered 9 Oct 2024 · hplc, purity, coa67How do I reconcile 97.6% from Janoshik with 97.1% from the supplier?answered 7 Feb 2026 · purity, batch-testing, coa67What does peptide mapping add for survodutide that a purity figure does not?accepted · answered 25 Jan 2026 · content-assay, purity, coa65Does aggregation dominate for a GLP-1 receptor agonist held at minus 80 °C?answered 15 Nov 2025 · peptide-stability, storage, hplc65Is a 97.6% result from PeptideMeter comparable to 95.2% from Janoshik?answered 30 Jul 2024 · purity, batch-testing, reference-standard65What does a 96.4% purity with a date of analysis attached let me conclude?answered 16 Jul 2024 · purity, coa, hplc64What does a sampling plan on a WXT report change about how I read it?answered 22 Nov 2025 · coa, batch-testing, vendor-vetting62Would you accept 98.4% on retatrutide from SSA without a content assay?accepted · answered 16 Nov 2025 · purity, content-assay, vendor-vetting61How does MKM compare to Chinese Peptide Company on documentation quality?accepted · answered 14 Jul 2024 · vendor-comparison, coa, vendor-vetting61How does SGN compare to Bachem Holding (Suzhou) on documentation quality?answered 22 Jul 2025 · vendor-comparison, coa, vendor-vetting61Is a 96.4% result from VendorInvestigate comparable to 99.1% from Janoshik?accepted · answered 8 Nov 2024 · purity, batch-testing, reference-standard60Is 1 mg weekly a defensible maintenance dose for a GLP-1 receptor agonist?answered 19 Dec 2025 · maintenance-dose, clinical-trials, dosing-math57Does aspartimide formation of liraglutide at minus 20 °C show up as a loss of content or of purity?answered 6 Jan 2025 · peptide-stability, content-assay, purity57Does dimerisation of cagrilintide at room temperature show up as a loss of content or of purity?answered 12 Jan 2025 · peptide-stability, content-assay, purity57Why do two laboratories report different purity for the same vial?answered 3 May 2026 · hplc, purity, reference-standard55Would you accept 97.9% on dulaglutide from GL Biochem without a content assay?answered 15 Jun 2024 · purity, content-assay, vendor-vetting54How does reference-standard error propagate into a liraglutide content figure?accepted · answered 3 Nov 2024 · reference-standard, content-assay, purity53Why is endotoxin testing separate from a sterility test?accepted · answered 12 Jul 2024 · endotoxin, sterility, coa52Is a 97.6% result from VendorInvestigate comparable to 99.1% from Medutest?answered 15 Dec 2024 · purity, batch-testing, reference-standard52What has Medutest published on WWB lots in the last year?answered 27 Aug 2025 · vendor-investigate, batch-testing, vendor-comparison51How do I reconcile 97.1% from Janoshik with 96.8% from the supplier?answered 10 Nov 2024 · purity, batch-testing, coa51What does PeptideMeter verification of Hunan Aslsen Technology actually cover?answered 12 Jul 2026 · vendor-investigate, vendor-vetting, coa50How long does retatrutide stay within specification at 2–8 °C once reconstituted?answered 31 May 2025 · peptide-stability, storage, shelf-life50What does a 99.1% purity with a sampling plan attached let me conclude?answered 8 Jun 2025 · purity, coa, hplc50What does a residual-solvent screen add for mazdutide that a purity figure does not?answered 22 Nov 2024 · content-assay, purity, coa50Why would Janoshik report 97.6% where the supplier certificate says something higher?answered 13 Dec 2024 · purity, hplc, batch-testing49How do I read an impurity table on a cagrilintide certificate against the 95.2% headline?answered 17 Aug 2025 · purity, coa, hplc48How much of the gross mass of a 2 mg orforglipron vial is actually peptide?answered 14 Jul 2024 · content-assay, water-content, acetate-content48What does a 97.9% purity with a batch certificate attached let me conclude?answered 26 Jun 2026 · purity, coa, hplc48What fraction of loss on retatrutide is lean mass according to TRIUMPH-3?answered 5 May 2025 · lean-mass, muscle-loss, dexa47Does oxidation dominate for liraglutide held at room temperature?answered 2 Nov 2024 · peptide-stability, storage, hplc47Why is "semaglutide sodium" on a COA treated as a red flag rather than a formatting quirk?accepted · answered 31 Dec 2024 · compounding, semaglutide, reference-standard47What should I make of a dulaglutide documentation package that has no sampling plan?answered 4 Mar 2025 · coa, vendor-vetting, batch-testing46How many freeze-thaw cycles will survodutide at 5 mg/mL tolerate?answered 11 Feb 2026 · freeze-thaw, peptide-stability, storage46Is 99.1% a realistic purity ceiling for cagrilintide given its chain length?accepted · answered 21 Jul 2026 · purity, hplc, peptide-mapping45What is the dead-space loss per draw with a 31G needle at 2.5 mg/mL?answered 13 Nov 2024 · dead-space, insulin-syringe, dosing-math44How many vials from a QST lot should I send for a sterility test?answered 7 Feb 2026 · batch-testing, coa, cost-analysis44How should I budget for an HPLC purity test across a twelve-month dulaglutide course?accepted · answered 17 May 2025 · batch-testing, cost-analysis, janoshik44Is 99.1% a realistic purity ceiling for retatrutide given its chain length?answered 19 Jan 2026 · purity, hplc, peptide-mapping44What does a list of related substances on an SSA report change about how I read it?accepted · answered 10 Jul 2026 · coa, batch-testing, vendor-vetting43How do I reconcile 99.1% from Janoshik with 96.4% from the supplier?answered 20 May 2025 · purity, batch-testing, coa43What does 96.4% purity on a wide-pore C18 column actually tell me about a GLP-1 receptor agonist vial?accepted · answered 29 Apr 2026 · hplc, purity, coa43Would you accept 99.1% on cagrilintide from CPC without a content assay?answered 21 May 2025 · purity, content-assay, vendor-vetting42What does co-elution of two species do to an LC-MS purity figure?answered 12 Jan 2025 · lc-ms, hplc, purity41How do I read an impurity table on a survodutide certificate against the 97.9% headline?answered 14 Jan 2025 · purity, coa, hplc41Is 8 mg/mL a sensible working concentration for orforglipron, or should I go lower?answered 19 Jul 2024 · diluent-volume, reconstitution, dosing-math41What does SOUL tell me about injection-site erythema at the 7 mg dose?answered 4 Mar 2026 · clinical-trials, injection-site-reaction, titration41Would you re-test survodutide after four weeks at room temperature, or accept the original certificate?accepted · answered 17 Apr 2026 · batch-testing, peptide-stability, coa40What accept/reject threshold would you set for dulaglutide before seeing the result?answered 1 Aug 2024 · batch-testing, harm-reduction, coa40What does SURMOUNT-1 tell me about headache at the 5 mg dose?answered 20 Jun 2025 · clinical-trials, titration39How many vials from a TFC lot should I send for an HPLC purity test?answered 27 Sept 2024 · batch-testing, coa, cost-analysis39Is 97.1% a realistic purity ceiling for survodutide given its chain length?accepted · answered 7 Sept 2024 · purity, hplc, peptide-mapping38How does tirzepatide behave on a wide-pore C18 column compared to cagrilintide?answered 19 Apr 2025 · hplc, purity, reference-standard38How many vials from a KP lot should I send for a quantified content assay?answered 1 Oct 2024 · batch-testing, coa, cost-analysis38Is 98.2% a realistic purity ceiling for semaglutide given its chain length?answered 18 Dec 2024 · purity, hplc, peptide-mapping38Is 99.1% a realistic purity ceiling for orforglipron given its chain length?accepted · answered 3 Jun 2025 · purity, hplc, peptide-mapping38Is a 97.9% result from Janoshik comparable to 99.1% from Medutest?answered 28 Jun 2024 · purity, batch-testing, reference-standard38Is a 97.9% result from Medutest comparable to 96.4% from PeptideMeter?answered 8 Oct 2025 · purity, batch-testing, reference-standard38What does 96.4% purity on a C18 column actually tell me about an ecnoglutide vial?answered 21 Jul 2025 · hplc, purity, coa37Does oxidation dominate for liraglutide held at 2–8 °C?answered 3 Sept 2025 · peptide-stability, storage, hplc37What does 95.2% purity on a wide-pore C18 column actually tell me about a mazdutide vial?answered 15 Jan 2025 · hplc, purity, coa36How do I model twelve months of survodutide across supply routes?answered 29 Apr 2026 · cost-analysis, insurance, compounding36How do I read a retatrutide chromatogram from Medutest beyond the headline number?answered 11 Nov 2024 · hplc, purity, coa36How should I budget for an HPLC purity test across a twelve-month orforglipron course?answered 22 Jul 2024 · batch-testing, cost-analysis, janoshik36Is 97.6% a realistic purity ceiling for tirzepatide given its chain length?accepted · answered 14 Mar 2026 · purity, hplc, peptide-mapping36Is 99.4% a realistic purity ceiling for ecnoglutide given its chain length?answered 4 Nov 2025 · purity, hplc, peptide-mapping36What does a 99.4% purity with a batch certificate attached let me conclude?answered 8 Mar 2025 · purity, coa, hplc35Does aggregation dominate for cagrilintide held at 25 °C?answered 20 May 2024 · peptide-stability, storage, hplc34Does a phosphate-buffered mobile phase change the purity number I get for semaglutide on a C18 column?answered 28 Jul 2025 · hplc, purity, reference-standard34Does aggregation dominate for a GLP-1 receptor agonist held at room temperature?answered 23 May 2026 · peptide-stability, storage, hplc34How many units on a U-100 insulin syringe is a 20 mg dose at 20 mg/mL?answered 7 Sept 2024 · dosing-math, insulin-syringe, reconstitution34How many vials from a QST lot should I send for an HPLC purity test?answered 30 Mar 2025 · batch-testing, coa, cost-analysis34What does 98.4% purity on a C18 column actually tell me about an ecnoglutide vial?answered 7 Jul 2025 · hplc, purity, coa34What does PeptideMeter verification of Chinese Peptide Company actually cover?answered 14 Apr 2025 · vendor-investigate, vendor-vetting, coa34Why would Janoshik report 96.4% where the supplier certificate says something higher?answered 29 Aug 2024 · purity, hplc, batch-testing34Why would PeptideMeter report 98.4% where the supplier certificate says something higher?accepted · answered 9 Nov 2025 · purity, hplc, batch-testing33Does aggregation dominate for cagrilintide held at 37 °C?answered 2 Jan 2025 · peptide-stability, storage, hplc33Does fibrillation dominate for semaglutide held at 37 °C?answered 28 Jul 2026 · peptide-stability, storage, hplc33How do I read a mazdutide chromatogram from Janoshik beyond the headline number?answered 13 Jul 2025 · hplc, purity, coa33Is a 96.4% result from Medutest comparable to 95.2% from Janoshik?answered 13 Jun 2026 · purity, batch-testing, reference-standard33Why does deamidation accelerate at 37 °C rather than proceeding linearly?accepted · answered 27 May 2026 · peptide-stability, storage, hplc33Would you accept 99.4% on cagrilintide from HJ without a content assay?answered 1 Feb 2025 · purity, content-assay, vendor-vetting32Does nausea at week four of survodutide usually resolve without a dose change?answered 2 Oct 2024 · nausea, titration, survodutide32How do I compute the +5 charge state m/z for a peptide of 4731.3 Da?answered 14 Mar 2025 · mass-spec, dosing-math, purity32How do I reconcile 99.1% from PeptideMeter with 97.9% from the supplier?answered 27 Jul 2026 · purity, batch-testing, coa32How does QST compare to Guangzhou JEEP Biotechnology on documentation quality?answered 23 Mar 2026 · vendor-comparison, coa, vendor-vetting32How many vials from an HJ lot should I send for an HPLC purity test?answered 25 Sept 2024 · batch-testing, coa, cost-analysis