Peptide testing glossary

A separation in which the stationary phase is non-polar and the mobile phase is polar, so components are retained according to how hydrophobic they are and are released as the solvent strength increases. It is the default mode for peptides because it separates on a property peptides differ in reliably.

See alsoGradientRetention time

The programmed change in mobile-phase composition across a run. A gradient lets one method separate components with very different retention in a reasonable time, and it is part of the method identity: the same column with a different gradient is a different method and can give a different purity figure.

See alsoReversed-phase chromatographyResolution

The time from injection to a peak apex under the stated method conditions. It is characteristic of a compound on a given method, which makes it useful supporting evidence for identity when compared against a reference run under identical conditions.

Retention time is not an identifier on its own. Different compounds can elute at the same time on one method, which is why identity rests on spectral comparison rather than on retention alone.

See alsoCo-elutionReference spectrum

The area of the principal peak expressed as a percentage of the total integrated detected response in the run, under stated method conditions and at a stated detection wavelength.

Area purity is not peptide content, not milligrams per vial, and not strength. It is normalised against what the detector saw, so material that does not absorb (salt, water, residual solvent) is not in the denominator at all.

See alsoPeptide contentIntegrationDetection wavelength

The process of defining where each peak starts and ends on the baseline and calculating the area between. Integration parameters are part of the method, and applying them inconsistently across a run is one of the failures data review exists to catch.

See alsoArea purityBaseline

The detector response with no analyte eluting. A stable baseline is what makes integration limits meaningful; drift or noise large relative to a small peak is a reason a run is repeated rather than reported.

See alsoIntegrationSignal-to-noise ratio

A numerical measure of how completely two adjacent peaks are separated, combining their spacing and their widths. A method requirement for resolution between the principal peak and its nearest neighbour is what makes a purity figure defensible.

See alsoCo-elutionSystem suitability

Two or more components leaving the column at the same time and integrating as a single peak. Co-elution is the structural reason a visually clean chromatogram is a statement about the method as much as about the sample.

A single sharp peak is not proof of a single compound. It is proof that this method did not separate whatever is in there.

See alsoResolutionOrthogonal method

A measure of peak asymmetry. Excessive tailing distorts integration and usually signals a column, mobile-phase, or sample-loading problem, so it is one of the checks a run has to pass before its results are reportable.

See alsoSystem suitabilityIon pairing

A dimensionless measure of column efficiency derived from peak width relative to retention. A falling plate count across a sequence is an early indicator that a column is degrading.

See alsoSystem suitability

The wavelength at which absorbance is recorded. Peptides are commonly read near 220 nm, where the peptide bond absorbs regardless of sequence, and near 280 nm where aromatic residues absorb.

A purity figure without its detection wavelength is not interpretable, because the same sample gives different area percentages at different wavelengths.

See alsoArea purityChromophoreDiode-array detection

The part of a molecule that absorbs ultraviolet or visible light. Detection wavelength is chosen around the analyte chromophore, which is why a non-peptide compound is usually not read at the low-ultraviolet peptide setting.

See alsoDetection wavelength

The use of a mobile-phase additive that pairs with charged sites on the analyte to improve retention and peak shape. Strongly basic peptides tail badly without it, and a tailing peak integrates unreliably.

See alsoTailing factor

A second method that separates or detects on a different physical principle from the first, so that what the first method could not distinguish, the second can. Orthogonal work is how a co-elution suspicion is resolved.

See alsoCo-elution

The height of an analyte response relative to the baseline noise around it. It is the basis on which limits of detection and quantitation are established, and it is why a very small peak may be visible but not reportable as a number.

See alsoLimit of detectionLimit of quantitation

An ultraviolet detector that records absorbance across a whole wavelength range at every point in a run rather than at one fixed wavelength. Full-spectrum HPLC with diode-array detection is the purity method run on every accepted sample, and it is why each peak carries a spectrum as well as an area.

A diode array measures light absorbed, not mass and not amount. A peak whose spectrum matches the expected compound is consistent with it; how many milligrams are in the vial is a separate measurement.

See alsoDetection wavelengthArea purityReference spectrum

A spectrum recorded from material of known identity, which a sample spectrum is compared against. An identity conclusion on a certificate from this laboratory is that comparison: the sample is confirmed against reference spectra using the techniques that suit the molecule, rather than by weighing the molecule.

A spectral match is a statement about consistency with the named expected compound. It cannot rule out a compound nobody asked about, which is why the expected identity is settled at scope review.

See alsoFTIR-ATRRaman spectroscopyCapillary electrophoresisUV-Vis spectroscopyScope review

Fourier-transform infrared spectroscopy with attenuated total reflectance. Infrared light passed through a crystal in contact with the sample is absorbed at frequencies characteristic of the bonds present, giving a pattern that can be matched against a reference spectrum with essentially no sample preparation.

See alsoReference spectrumRaman spectroscopy

Measurement of the small frequency shifts in light scattered by a sample, which report on the same molecular vibrations infrared absorption does but under different selection rules. Bonds that respond weakly in infrared often respond strongly in Raman, which is why the two are read together rather than as alternatives.

See alsoFTIR-ATRReference spectrum

Separation of components by how fast they migrate through a narrow buffer-filled capillary under an electric field, with ultraviolet detection at the far end, written CE-UV. It sorts on charge and size rather than on hydrophobicity, so it separates on a different principle from reversed-phase chromatography.

See alsoOrthogonal methodReference spectrum

Measurement of absorbance across ultraviolet and visible wavelengths, giving the shape of a compound’s absorbance rather than a single reading at one wavelength. It is most informative where the analyte has a distinct chromophore, and least where it does not.

See alsoChromophoreReference spectrum

Additional work sent to a contract laboratory when a result looks anomalous and the in-house evidence does not settle it, most often LC-MS. Where confirmatory work is used, the contract laboratory is named on the certificate.

Confirmatory testing is not part of the standard test and is not run on every sample. There is no in-house mass spectrometer, so no certificate from this laboratory carries a mass spectrum.

See alsoOrthogonal methodReference spectrum

A soft ionisation technique that transfers molecules from solution into the gas phase as charged ions without breaking them apart. Its softness is what makes it suitable for peptides: the intact molecule survives to be measured.

See alsoCharge stateMass-to-charge ratio

The quantity a mass analyser actually sorts on, written m/z. It is the ion mass divided by its number of charges, which is why a molecule carrying three protons appears at roughly a third of the position of the same molecule carrying one.

See alsoCharge stateDeconvolution

The number of charges an ion carries, written as [M+nH]ⁿ⁺ for a peptide that has picked up n protons. A peptide typically appears as a series of charge states rather than a single line.

See alsoDeconvolutionElectrospray ionisation

The calculation that recovers a single molecular mass from a series of charge states. A consistent series (every state pointing at the same underlying mass) is what makes an assignment credible rather than a coincidence.

See alsoCharge stateObserved mass

The molecular mass recovered from a sample spectrum, reported alongside the theoretical mass and the difference between them.

Certificates from this laboratory do not carry an observed mass, because identity here is confirmed against reference spectra rather than by mass measurement. An observed mass on a report is a mass-spectrometric result from whoever produced it.

See alsoTheoretical massMass accuracyReference spectrum

The molecular mass calculated for the expected compound from reference data, on a stated basis, usually the free base rather than the salt. It is a property of the molecule named at scope review, not a measurement, and it is the value any mass result would be compared against.

The theoretical mass depends on the salt form and counter-ion basis chosen. A comparison against the wrong basis produces an apparent mismatch that is a bookkeeping error, not a product problem.

See alsoObserved massCounter-ion

How close a measured mass is to the true mass, usually expressed in parts per million. It depends on current calibration, which is why calibration status is a system suitability condition.

See alsoSystem suitability

The cluster of signals about one nominal mass caused by naturally occurring heavier isotopes, principally carbon-13. A molecule with tens of carbons never produces a single clean line, and the pattern itself is supporting evidence.

Reduction of an analyte signal caused by co-eluting material competing for charge during ionisation. It can depress or entirely remove a real signal, which is why an absent signal is not by itself evidence of absent material.

See alsoMatrix effectCo-elution

Having the same nominal mass as another compound. Isobaric species cannot be told apart by mass measurement alone and need chromatographic separation or an orthogonal approach.

See alsoOrthogonal methodStereoisomer

A molecule with the same atoms and connectivity but a different three-dimensional arrangement. D-amino-acid and retro-inverso constructs share the mass of their natural-sequence counterparts, so mass evidence cannot separate them.

See alsoIsobaricRetro-inverso peptide

A peptide built from D-amino acids in reversed sequence order, designed to present a similar side-chain topology to the natural peptide. It has the same molecular mass as the natural sequence, which is why the construct type has to be stated on the request.

See alsoStereoisomer

The measured amount of target peptide in the sample as submitted, determined against a calibrated reference standard and expressed on a stated basis. It is requested rather than run by default, and it depends on a suitable reference standard being obtainable.

Content is not purity. A vial can be 99% pure and hold a third of its labelled milligrams, because purity describes the composition of what is there and content describes how much of it there is.

See alsoArea purityLabel claimPeptide base versus gross salt

The amount the vial states it contains. A content result is reported alongside it so the comparison is explicit rather than left to the reader.

See alsoPeptide content

Two different bases for expressing content. Peptide base excludes counter-ion and residual moisture; gross salt includes them. The same vial gives two different numbers depending on which is used, so the basis is agreed at scope review and printed on the certificate.

See alsoCounter-ionPeptide content

The ion paired with a charged peptide in its salt form, commonly acetate or trifluoroacetate. It contributes real mass to the powder in the vial while contributing no peptide, and its share is proportionally larger on short peptides.

See alsoPeptide base versus gross saltResidual moisture

Water retained in a lyophilized powder. Like counter-ion, it is weight in the vial that is not peptide, and hygroscopic material picks up more of it every time a vial is opened.

See alsoCounter-ionLyophilized

Material of known identity and assigned value used to calibrate a quantitative measurement. A content result can be no better than the standard behind it, and for some research-stage compounds no suitable standard is obtainable.

See alsoCalibration curvePeptide content

The relationship between analyte concentration and detector response, built from standards across a working range. Sample results are interpolated on it; a result extrapolated beyond the highest standard is not reported as though it were interpolated.

See alsoLinearityWorking range

How well detector response tracks concentration in a straight line across the working range. It is a pass condition for a quantitative run rather than a descriptive statistic.

See alsoCalibration curve

The concentration span over which the method has been shown to perform acceptably. Results are only reported inside it.

See alsoCalibration curveLimit of quantitation

The proportion of a known added amount that the whole method actually finds. It tests the sample preparation as well as the instrument, which is why a spiked recovery check is run rather than only an instrument standard.

See alsoMatrix effect

The lowest amount that can be reliably distinguished from noise, but not necessarily measured accurately. Something detected above this limit and below the quantitation limit is reported as detected rather than as a number.

See alsoLimit of quantitationSignal-to-noise ratio

The lowest amount that can be measured with acceptable precision and accuracy. It is the floor on any reported numeric result, and it is why a certificate says "less than" a value rather than reporting a smaller one.

See alsoLimit of detectionReporting limit

The threshold at or above which the laboratory will report a numeric value for a given analyte on a given method. It is stated on the certificate so that a "not detected" result carries a number a reader can evaluate.

"Not detected" never means "none present". It means none present above the stated reporting limit under the method used.

See alsoLimit of quantitation

The range within which the true value is expected to lie, given the known sources of variation in the measurement. Any quantitative figure is a best estimate with an uncertainty around it, not an exact count.

The influence everything other than the analyte has on the measurement: suppressing ionisation, interfering with detection, or reducing recovery. It is the reason a finished formulation is a much harder submission than raw powder.

See alsoIon suppressionRecovery

A lipopolysaccharide component of Gram-negative bacterial cell walls, measured because it is heat-stable and survives processes that kill the organism itself. It is measured here by kinetic chromogenic LAL, with recombinant factor C available on request.

An endotoxin result is not a sterility result. It measures a cell-wall component and does not detect viable organisms of any kind.

See alsoEndotoxin unitSterility

The unit an endotoxin result is expressed in, written EU, defined against a reference standard endotoxin and normally reported per millilitre or per stated sample basis.

See alsoBacterial endotoxin

A spiked sample run alongside the test to demonstrate that the sample itself is not inhibiting or enhancing the reaction. Its recovery is reported, because without it a clean endotoxin result cannot be distinguished from an inhibited one.

See alsoBacterial endotoxin

The greatest dilution at which a sample can still be tested and remain capable of detecting endotoxin at the stated limit. Diluting past it makes a pass meaningless.

See alsoBacterial endotoxin

Total aerobic microbial count and total yeast and mould count: two separate enumerations run on different media at different temperatures, reported separately. Canada Peptide Testing does not offer microbial enumeration, and the term is defined here only so a report carrying it can be read.

Enumeration is not a compendial sterility test, and only organisms that grow on the chosen media under the chosen conditions are counted.

See alsoColony-forming unitSterility

One countable colony on a plate, written CFU, taken to represent one viable organism or clump capable of growing under the test conditions. It is the unit an enumeration result is expressed in.

See alsoTAMC and TYMC

The absence of viable organisms, established only by a specific compendial sterility test under defined conditions. It is not offered as part of any panel on this site.

Neither a low endotoxin result nor a low microbial count establishes sterility. They are different questions answered by different tests.

See alsoBacterial endotoxinTAMC and TYMC

A metal or metalloid present in a material. Lead, arsenic, cadmium and mercury are screened by atomic absorption, graphite furnace and flame, and reported per element against its own reporting limit; where a screen warrants it, ICP-MS confirmation is sent to a contract laboratory.

Only the elements in the accepted scope are measured. An element that was not on the list is not reported as absent, because it was never looked for.

See alsoReporting limitSpecification

A sample-free preparation carried through the entire process to establish what the process itself contributes. It is what separates contamination in the sample from contamination in the laboratory.

The released document identifying the sample, the methods run on it, the results with their basis, the dates, the reviewer, and the stated limitations. It is a record about one specific sample.

A COA is not transferable to another vial, batch, or lot because the label matches. It attaches to the sample that was received.

See alsoSample IDVerification record

The unique identifier issued with an accepted request that links the request, the intake, the status history, the analysis, the review, and the released certificate.

See alsoChain of custody

The recorded sequence of who held a sample and what was done to it, from arrival to disposal. It is what makes a result traceable to a specific arrival and a specific run.

See alsoSample ID

The set of analytical questions the laboratory has agreed to answer for a given sample, settled in writing before the sample is shipped. The scope bounds what any resulting conclusion can address.

See alsoScope review

The chemist-led review of a request before acceptance, which settles method fit, required quantity, matrix workability, and what the result will and will not support.

See alsoScopeFeasibility review

The assessment applied to an unlisted compound, unusual matrix, or non-standard request, deciding whether the work can be done at all and on what terms.

See alsoScope review

The set of checks a run must pass before any of its results are reportable: blanks, replicate standards, resolution, symmetry, calibration performance, recovery. These are pass conditions, not diagnostics.

See alsoResolutionLinearityRecovery

An agreed acceptance limit against which a measured value is judged. Without one, the laboratory reports the measured value and does not imply a universal acceptance threshold.

"Pass" is only meaningful when a specification and its source are stated. A pass with no named specification is a claim about nothing.

See alsoReporting limit

The public page a released certificate resolves to by report number and QR code, letting someone who did not receive the original file check that the document matches the laboratory record.

A verification page confirms the document is genuine and unaltered. It does not widen the scope of the testing behind it.

See alsoCertificate of Analysis

The property of records being attributable, legible, contemporaneous, original, and accurate, and remaining complete, consistent, enduring, and available, the set usually abbreviated ALCOA+.

The international standard for the competence of testing and calibration laboratories. Accreditation to it is granted by an accreditation body over a defined scope of named methods.

Canada Peptide Testing does not hold this accreditation. Its procedures are informed by the standard’s principles, and alignment with principles is not certification.

A statement that the material and its result are for laboratory research purposes, and that no result establishes clinical safety, efficacy, sterility, regulatory status, or fitness for use in or on a person or animal.

Freeze-dried to a solid powder or cake. It is the preferred submission form because it is stable in transit and because content calculations do not have to account for a solvent volume.

See alsoResidual moistureReconstitution

Dissolving a lyophilized product in a diluent. Samples should not be reconstituted before shipping unless the laboratory has approved it, because degradation and adsorption continue in solution during transit.

See alsoLyophilizedDiluent

The liquid used to reconstitute or dilute a product. A diluent submitted on its own is tested for endotoxin and any stated preservative concentration rather than for peptide identity.

See alsoReconstitution

Everything in the sample other than the analyte. Matrix decides how hard a sample is to prepare and how much interference the measurement has to survive, which is why it is asked about before acceptance.

See alsoMatrix effect

The amount the vial is stated to contain, as printed on the label. It is what a measured content figure is compared against, so it is asked for on the request rather than inferred.

See alsoLabel claim

A vial containing more than one expected analyte. Blends are handled under a distinct panel because overall purity and per-component findings are different results and are reported separately.

See alsoBlind identification

Investigation of a sample with no declared expected identity, using spectral and chromatographic evidence against available comparison data. Not every unknown can be resolved conclusively.

See alsoBlend

Material left after analysis, kept for a defined period after release so a query can be investigated against what was actually tested rather than against a fresh vial.