[{"data":1,"prerenderedAt":408},["ShallowReactive",2],{"article-\u002Fresearch\u002Finterpreting-hplc-chromatograms":3,"article-compounds-\u002Fresearch\u002Finterpreting-hplc-chromatograms":371,"article-more-\u002Fresearch\u002Finterpreting-hplc-chromatograms":393},{"id":4,"title":5,"body":6,"description":341,"extension":342,"faq":343,"meta":353,"navigation":354,"path":355,"publishedAt":356,"readingMinutes":357,"relatedCompounds":358,"seo":362,"stem":363,"tags":364,"updatedAt":369,"__hash__":370},"research\u002Fresearch\u002Finterpreting-hplc-chromatograms.md","Reading an HPLC Chromatogram: What the Trace Shows That the Percentage Doesn't",{"type":7,"value":8,"toc":324},"minimark",[9,13,18,21,29,37,41,44,51,73,76,80,85,88,94,100,104,107,114,118,121,147,153,157,160,166,172,178,181,185,188,191,194,220,223,227,230,236,247,250,254,299,302,306,317],[10,11,12],"p",{},"A purity figure is one number extracted from a picture by a person who made\nseveral judgement calls on the way. The picture contains the judgements. This is\nhow to read it.",[14,15,17],"h2",{"id":16},"what-the-trace-is","What the trace is",[10,19,20],{},"Reversed-phase HPLC pushes a dissolved sample through a column packed with a\nnon-polar stationary phase — for peptides, usually C18-derivatised silica. A\nmobile phase gradient, typically water to acetonitrile with a small amount of\nacid, gradually increases the eluting strength.",[10,22,23,24,28],{},"Components that interact weakly with the stationary phase leave early. Strongly\ninteracting ones leave later. A UV detector at the column outlet records\nabsorbance over time, and the resulting trace is the chromatogram: ",[25,26,27],"strong",{},"time on the\nx-axis, detector response on the y",".",[10,30,31,32,28],{},"The acid — usually trifluoroacetic acid — is there to keep basic residues\nprotonated and suppress interactions with residual silanols on the silica. It is\nalso the origin of the counter-ion salt that ends up in the final product. See\n",[33,34,36],"a",{"href":35},"\u002Fresearch\u002Fnet-peptide-content-vs-purity","net peptide content versus purity",[14,38,40],{"id":39},"the-baseline","The baseline",[10,42,43],{},"Start at the bottom of the trace, not the top.",[10,45,46,47,50],{},"A good baseline is ",[25,48,49],{},"flat and low",", with small, even noise. What you are looking\nfor is anything that is not that:",[52,53,54,61,67],"ul",{},[55,56,57,60],"li",{},[25,58,59],{},"Drift"," — a baseline that climbs steadily through the run. Some drift is\nnormal on a gradient because acetonitrile and water have different UV\nabsorbance, but pronounced drift makes integration ambiguous, because where the\nbaseline is drawn determines every peak area on the page.",[55,62,63,66],{},[25,64,65],{},"Wander"," — irregular rise and fall, suggesting temperature instability or a\npoorly mixed mobile phase.",[55,68,69,72],{},[25,70,71],{},"Noise"," — a thick, fuzzy baseline. This sets the detection limit: impurities\nbelow the noise floor are not being counted, which flatters the purity figure.",[10,74,75],{},"A certificate showing a chromatogram with the y-axis scaled so that everything\nexcept the main peak is a flat line at zero is not showing you the baseline. It\nis hiding it.",[14,77,79],{"id":78},"peak-shape","Peak shape",[81,82,84],"h3",{"id":83},"symmetry","Symmetry",[10,86,87],{},"An ideal peak is symmetric — Gaussian, rising and falling at the same rate.",[10,89,90,93],{},[25,91,92],{},"Tailing"," — a peak that rises sharply and trails off — is the most common\ndeviation in peptide work. Causes include secondary interactions with residual\nsilanols, column overload, or a column nearing the end of its life. Tailing\nmatters because a tailing main peak overlaps whatever elutes after it, and the\npurity figure then depends on where the analyst decided the tail ended and the\nnext peak began.",[10,95,96,99],{},[25,97,98],{},"Fronting"," — a gradual rise and sharp fall — usually indicates column overload\nor a solvent mismatch between sample and mobile phase.",[81,101,103],{"id":102},"width","Width",[10,105,106],{},"Peak width is not a quality indicator on its own. Larger peptides produce broader\npeaks; shallower gradients produce broader peaks. A 44-residue tesamorelin peak\nwill be visibly broader than a 5-residue ipamorelin peak on any comparable\nmethod, and neither observation says anything about purity.",[10,108,109,110,113],{},"Broad ",[25,111,112],{},"and tailing"," is a different matter, because it degrades the resolution\nthat the whole measurement rests on.",[14,115,117],{"id":116},"resolution-the-property-that-determines-whether-the-number-means-anything","Resolution: the property that determines whether the number means anything",[10,119,120],{},"Resolution is how completely two adjacent peaks are separated. It is what\ndetermines whether an impurity is counted as an impurity or absorbed into the\nmain peak.",[52,122,123,129,135,141],{},[55,124,125,128],{},[25,126,127],{},"Baseline resolved"," — the trace returns to baseline between two peaks. Their\nareas are unambiguous.",[55,130,131,134],{},[25,132,133],{},"Partially resolved"," — a visible valley, but the trace does not return to\nbaseline. Integration requires a decision about where to split them.",[55,136,137,140],{},[25,138,139],{},"Shoulder"," — a bump on the side of the main peak. There are two components\nand the method cannot separate them.",[55,142,143,146],{},[25,144,145],{},"Co-eluting"," — no visible indication at all. The impurity is inside the main\npeak and is being counted as product.",[10,148,149,152],{},[25,150,151],{},"A shoulder on the main peak is the single most informative feature on a peptide\nchromatogram."," In peptide synthesis, the impurities that elute closest to the\ntarget are the ones structurally most similar to it — single-residue deletion\nsequences, diastereomers from partial racemisation, incompletely modified\nspecies. These are precisely the impurities you would most want to know about,\nand precisely the ones a purity percentage can quietly absorb.",[14,154,156],{"id":155},"where-the-impurities-sit","Where the impurities sit",[10,158,159],{},"The retention time of an impurity relative to the main peak carries information.",[10,161,162,165],{},[25,163,164],{},"Early-eluting (before the main peak)"," — more polar than the target. Commonly\ntruncated sequences that lost hydrophobic residues, deprotection by-products, or\nhydrolysis products.",[10,167,168,171],{},[25,169,170],{},"Late-eluting (after the main peak)"," — more hydrophobic. Commonly incompletely\ndeprotected species still carrying a protecting group, dimers, or aggregated\nmaterial. On lipidated peptides, over-conjugated species carrying an extra fatty\nacid chain.",[10,173,174,177],{},[25,175,176],{},"Immediately adjacent"," — structurally near-identical. The deletion sequences\nand diastereomers described above.",[10,179,180],{},"A chromatogram with a clean baseline and two small, well-separated, distant\nimpurity peaks describes a better material than one with the same purity\npercentage and an unresolved shoulder — even though both certificates might say\n99.1%.",[14,182,184],{"id":183},"the-integration-boundaries","The integration boundaries",[10,186,187],{},"Integration is where the numbers are made, and where the judgement lives.",[10,189,190],{},"The analyst — or the software, with the analyst's parameters — decides where each\npeak starts and ends, and where the baseline runs beneath it. Reasonable people\nmake different choices, and those choices propagate directly into the reported\npercentage.",[10,192,193],{},"Practices worth noticing:",[52,195,196,202,208,214],{},[55,197,198,201],{},[25,199,200],{},"Boundaries placed to absorb a shoulder"," into the main peak.",[55,203,204,207],{},[25,205,206],{},"A high detection threshold"," that drops small peaks from the calculation\nentirely.",[55,209,210,213],{},[25,211,212],{},"A truncated time window"," that ends the run before late-eluting hydrophobic\nimpurities have emerged. If the chromatogram stops two minutes after the main\npeak, anything slower is not in the total.",[55,215,216,219],{},[25,217,218],{},"A y-axis scaled to the main peak",", which visually flattens everything else\nto nothing.",[10,221,222],{},"None of these are necessarily dishonest. All of them raise the reported number.\nNone of them are visible in the number itself.",[14,224,226],{"id":225},"detection-wavelength","Detection wavelength",[10,228,229],{},"Usually printed in small type, and it changes what the trace can see.",[10,231,232,235],{},[25,233,234],{},"214 nm"," detects the peptide bond, which every peptide has. This is the\nstandard for purity work because it responds to all peptide material roughly in\nproportion to size.",[10,237,238,241,242,246],{},[25,239,240],{},"280 nm"," detects aromatic residues — tryptophan, tyrosine, phenylalanine. Useful\nfor quantitation when a peptide contains them, but as a ",[243,244,245],"em",{},"purity"," wavelength it is\npartially blind: any impurity lacking aromatic residues is invisible, and\ninvisible impurities do not count against the purity figure.",[10,248,249],{},"A purity figure from a 280 nm run on a peptide with a single tryptophan is not\ncomparable to one from a 214 nm run, and is systematically more flattering.",[14,251,253],{"id":252},"a-reading-order","A reading order",[255,256,257,263,269,275,281,287,293],"ol",{},[55,258,259,262],{},[25,260,261],{},"Baseline"," — flat, low, quiet?",[55,264,265,268],{},[25,266,267],{},"Main peak shape"," — symmetric, or tailing?",[55,270,271,274],{},[25,272,273],{},"Shoulders"," — anything unresolved on the sides?",[55,276,277,280],{},[25,278,279],{},"Impurity peaks"," — how many, where, how well separated?",[55,282,283,286],{},[25,284,285],{},"Run length"," — does the trace continue well past the main peak?",[55,288,289,292],{},[25,290,291],{},"Axis labels"," — is the wavelength stated, is the y-axis scaled sensibly?",[55,294,295,298],{},[25,296,297],{},"Then"," read the percentage.",[10,300,301],{},"The number is the last thing to look at, not the first.",[14,303,305],{"id":304},"what-a-chromatogram-cannot-tell-you","What a chromatogram cannot tell you",[10,307,308,309,312,313,28],{},"It cannot identify the main peak. A beautifully resolved, symmetric, 99.6% peak\nis a beautifully resolved 99.6% peak of ",[243,310,311],{},"something",", and establishing what\nrequires\n",[33,314,316],{"href":315},"\u002Fresearch\u002Fmass-spectrometry-peptide-identity","mass spectrometry",[10,318,319,320,323],{},"It also says nothing about the non-peptide mass — salt and water are essentially\ninvisible at peptide detection wavelengths, which is why\n",[33,321,322],{"href":35},"net peptide content"," is a separate\nmeasurement.",{"title":325,"searchDepth":326,"depth":326,"links":327},"",2,[328,329,330,335,336,337,338,339,340],{"id":16,"depth":326,"text":17},{"id":39,"depth":326,"text":40},{"id":78,"depth":326,"text":79,"children":331},[332,334],{"id":83,"depth":333,"text":84},3,{"id":102,"depth":333,"text":103},{"id":116,"depth":326,"text":117},{"id":155,"depth":326,"text":156},{"id":183,"depth":326,"text":184},{"id":225,"depth":326,"text":226},{"id":252,"depth":326,"text":253},{"id":304,"depth":326,"text":305},"A purity figure is one number extracted from a picture. How to read the picture — baseline, peak shape, resolution, where the impurities sit, and what an integration boundary can hide.","md",[344,347,350],{"question":345,"answer":346},"Why does the chromatogram matter if the purity percentage is on the certificate?","The percentage is a single number derived from the trace by a person making judgement calls — where to set the baseline, where to place integration boundaries, whether a shoulder is one peak or two. The chromatogram shows those judgements. Two analysts can extract meaningfully different percentages from the same data, and only the trace reveals which choices were made.",{"question":348,"answer":349},"What does a shoulder on the main peak indicate?","An unresolved component eluting very close to the target — most often a single-residue deletion sequence or a diastereomer. Whether it is integrated separately or absorbed into the main peak can change the reported purity by a percentage point or more, which is exactly why it matters that the shoulder is visible.",{"question":351,"answer":352},"Is a wide peak a sign of poor quality?","Not necessarily. Peak width scales with molecular size and depends on the gradient, so a 44-residue lipidated peptide will always produce a broader peak than a 5-residue one on the same method. What matters is whether the peak is broad and symmetric, or broad and tailing — the second suggests secondary interactions or column degradation, and degrades the resolution the purity figure depends on.",{},true,"\u002Fresearch\u002Finterpreting-hplc-chromatograms","2026-08-20",9,[359,360,361],"bpc-157","ipamorelin","tesamorelin",{"title":5,"description":341},"research\u002Finterpreting-hplc-chromatograms",[365,366,367,368],"HPLC","chromatography","quality control","COA",null,"kl4vgze9YD4BD-iFuGjAyUhGHdDsfNTKPWDRJrYBCN4",[372,380,387],{"path":373,"name":374,"alsoKnownAs":375,"summary":376,"category":377,"molecularWeight":378,"purity":379},"\u002Fcompounds\u002Fbpc-157","BPC-157","Body Protection Compound 157 · PL 14736","A synthetic 15-amino-acid sequence derived from human gastric juice protein BPC, studied extensively in tissue repair and angiogenesis models.","Repair & Recovery","~1,419.5 Da","≥99%",{"path":381,"name":382,"alsoKnownAs":383,"summary":384,"category":385,"molecularWeight":386,"purity":379},"\u002Fcompounds\u002Fipamorelin","Ipamorelin","NNC 26-0161","A selective growth hormone secretagogue receptor agonist, notable for acting on the ghrelin receptor without the appetite and cortisol effects of earlier secretagogues.","Growth Hormone","~711.9 Da",{"path":388,"name":389,"alsoKnownAs":390,"summary":391,"category":385,"molecularWeight":392,"purity":379},"\u002Fcompounds\u002Ftesamorelin","Tesamorelin","TH9507 · trans-3-hexenoyl-GHRH(1-44)","A stabilised analogue of full-length growth hormone-releasing hormone, distinguished by retaining all 44 residues rather than the 1-29 fragment.","~5,136 Da",[394,399,404],{"path":395,"title":396,"description":397,"publishedAt":398},"\u002Fresearch\u002Fchoosing-a-peptide-supplier-australia","Choosing a Research Peptide Supplier in Australia: A Checklist","Fourteen questions that separate suppliers with a real quality process from suppliers with a good website — covering documentation, testing claims, provenance, handling and the language they use.","2026-08-24",{"path":400,"title":401,"description":402,"publishedAt":403},"\u002Fresearch\u002Fcounterfeit-peptides-australia","Counterfeit and Substituted Research Peptides: What Actually Gets Faked","Substitution, dilution, wrong-form supply and underfilled vials — the four ways research peptides are misrepresented, why each is hard to detect, and which analytical test catches which.","2026-08-23",{"path":405,"title":406,"description":407,"publishedAt":403},"\u002Fresearch\u002Fresearch-peptides-australia-legal-status","Research Peptides in Australia: The Regulatory Position","How the TGA, the Poisons Standard and import rules apply to peptides supplied for laboratory research in Australia — what research-use-only means legally, and where the line sits.",1787473952822]