Methods library
Every analytical method you are likely to see on a peptide certificate: what it answers, what it cannot, what it outputs and how it is written on a COA. Analysis for Tested.ph records is performed by a partner laboratory.
Offered when testing opens. The methods behind every standard Tested.ph record, plus the optional endotoxin test.
- HPLC-UVHigh-performance liquid chromatography with UV detectionHPLC-UV separates the components of a dissolved peptide sample on a packed column and measures each one by how strongly it absorbs ultraviolet light, which gives a purity figure by peak area and, against a reference standard, a measured amount.
- LC-MSLiquid chromatography mass spectrometryLC-MS separates a peptide sample by liquid chromatography and then weighs the molecules coming off the column with a mass spectrometer, so the observed mass of the main peak can be compared with the theoretical mass of the peptide on the label.
- LAL endotoxinBacterial endotoxins test by Limulus amebocyte lysate (gel clot, kinetic turbidimetric, kinetic chromogenic) and recombinant factor CThe bacterial endotoxins test measures endotoxin in a sample by letting it trigger a clotting enzyme cascade from horseshoe crab blood cells, read as a gel, as rising turbidity or as released colour, while recombinant factor C methods use a lab-made version of the first enzyme and read fluorescence instead.
Planned. Methods that answer real buyer questions and are planned but not yet offered.
- HRMSHigh-resolution mass spectrometryHigh-resolution mass spectrometry measures a molecule's mass precisely enough, often to within a few parts per million, and separates peaks finely enough to resolve its isotope pattern, so a peptide's identity can be confirmed far more tightly than with a nominal-mass instrument.
- Amino acid analysisQuantitative amino acid analysis after acid hydrolysisAmino acid analysis breaks a peptide down into its individual amino acids with hot acid, measures how much of each is present, and uses the stable ones to work out how much peptide was in the weighed powder and whether the composition fits the expected sequence.
- Karl Fischer titrationKarl Fischer titration for water contentKarl Fischer titration measures water through a reaction in which iodine is consumed only in the presence of water, so the amount of iodine used, or the electric current needed to generate it, gives the water content directly.
- Counter-ion contentCounter-ion content (trifluoroacetate, acetate, chloride) by ion chromatography, 19F NMR, HPLC with ELSD and related methodsCounter-ion testing measures the acetate, trifluoroacetate (TFA) or chloride ions that sit alongside a charged peptide in its salt form, using techniques such as ion chromatography, fluorine NMR or HPLC with an evaporative light-scattering detector, so the non-peptide share of the powder can be accounted for.
Explained, not offered. Methods you will meet on certificates from other labs. Tested.ph explains them so you can read those reports.
- MALDI-TOFMatrix-assisted laser desorption/ionisation time-of-flight mass spectrometryMALDI-TOF mixes a peptide sample with a light-absorbing matrix, fires a laser at the dried spot to lift the molecules into the gas phase as mostly singly charged ions, and times how long they take to fly down a tube, which gives a fast mass check without a chromatography step.
- Peptide mappingPeptide mapping by enzymatic digestion and LC-MS or LC-UVPeptide mapping cuts a peptide or protein into smaller fragments with an enzyme, separates the fragments by liquid chromatography and identifies each one, so the pattern of fragments confirms the sequence region by region instead of relying on one intact mass.
- Sterility testingSterility test by membrane filtration or direct inoculation (USP <71>, Ph. Eur. 2.6.1, JP 4.06)The pharmacopoeial sterility test places a sample, or a filter it has passed through, into two growth media and incubates them for at least 14 days, and the sample complies only if no microbial growth appears.
- ICP-MS (elemental impurities)Inductively coupled plasma mass spectrometry for elemental impurities (ICH Q3D, USP <232>/<233>)ICP-MS digests a sample in acid, sprays it into an argon plasma hot enough to break every molecule into charged atoms, and counts the ions of each element by mass, which lets a laboratory measure trace metals such as lead, cadmium, arsenic and mercury against the limits set by ICH Q3D.
- GC residual solventsGas chromatography for residual solvents, usually by headspace sampling (ICH Q3C, USP <467>)Residual solvent testing heats a sealed vial of the sample so that volatile solvents left over from manufacture move into the air above it, sends that vapour into a gas chromatograph, and measures each solvent against the class-based limits in ICH Q3C.
- Appearance and solubilityAppearance (description) and solubility or appearance of solutionAppearance and solubility testing records what a sample looks like, its physical state, colour and, for a freeze-dried vial, the condition of the cake, and whether it dissolves fully and clearly in a stated solvent, which can flag handling or manufacturing problems but cannot confirm what the peptide is.
How results become grades
The Tested Index turns identity, purity and amount results into vendor grades with a published formula. Read the scoring methodology and the rules on how rankings work. Who runs the analysis is on partner labs; how these methods appear on a certificate is taught in COA School; method choices are compared in HPLC vs LC-MS.