Glossary

172 terms you will meet on test reports, certificates and Tested.ph records, in plain English. Terms with a fuller explanation link to it.

A

Accreditation: Formal recognition by an accreditation body that a laboratory is competent to perform specific tests, usually assessed against ISO/IEC 17025. It covers only the methods in the lab's scope, so an accredited lab can still report tests that are outside it.See also: ISO/IEC 17025, PAB (Philippine Accreditation Bureau), ILAC, CATO (certificate of authority to operate)
Accuracy: How close a measured value is to the true or accepted reference value. It is usually shown by measuring samples of known content and checking the recovery.See also: Precision, Method validation, Reference standard
Acetate salt: A peptide paired with acetate counter-ions, usually produced by exchanging the TFA from synthesis. Many peptide medicines use the acetate form.See also: TFA salt, Hydrochloride salt, Ion exchange, Counter-ion
Acetylation: Adding an acetyl group, most often to the N-terminus of a peptide. It can be part of the intended structure, or a capping step during synthesis that leaves acetylated truncated sequences as impurities.See also: N-terminus, Truncated sequence, Solid-phase peptide synthesis (SPPS)
Amidation: A modification where the C-terminal carboxylic acid is replaced by an amide. In synthesis it is built in by choosing an amide-forming resin, and getting it wrong produces a molecule that differs from the target by a small, measurable mass.See also: C-terminus, Solid-phase peptide synthesis (SPPS), Monoisotopic mass
Amino acid: The building block of peptides and proteins: a molecule with an amine group, a carboxylic acid group and a side chain that gives each amino acid its character. Most occur in left-handed (L) and right-handed (D) forms.See also: Peptide, Residue, Racemisation
Amino acid analysis: Breaking a peptide fully into its amino acids with acid and measuring how much of each is present. It confirms the composition and gives an absolute peptide quantity, which is why it is a standard way to determine net peptide content.See also: Net peptide content, Assay, Peptide mapping
Anonymous purchase: A vial Tested.ph buys as an ordinary customer, without the vendor knowing it will be tested. Only anonymous purchases feed the Tested Index, because the vendor could not choose which vial to send.See also: Tested Index, Vendor-submitted, Consumer-submitted, Blind sample
Appearance test: A visual check of the powder and vial: colour, form and any visible particles, sometimes with a check of how the powder dissolves. It catches obvious problems but cannot confirm identity, purity or amount.See also: Cake, Identity test, COA (certificate of analysis)
Area percent: One peak's area divided by the total area of all integrated peaks, times one hundred. Most peptide purity figures are area percent results, so they depend on which peaks were integrated and where the baseline was drawn.See also: HPLC purity, Peak area, Baseline
Aspartimide: A ring-shaped by-product formed at aspartic acid residues during Fmoc synthesis, especially where aspartic acid is followed by glycine. It can reopen into rearranged forms of the peptide that are hard to separate from the target.See also: Fmoc chemistry, Deamidation, Related substances
Assay: A quantitative test that measures how much of the intended substance is present, usually against a reference standard. On a peptide certificate it answers how many milligrams are in the sample, which purity does not.See also: Quantification, Reference standard, Label claim, Calibration curve
Average mass: The mass of a molecule calculated from the natural mix of isotopes of each element. It is the molecular weight usually printed on labels and used for weighing, and it is slightly higher than the monoisotopic mass, so the two should not be compared with each other.See also: Monoisotopic mass, Dalton (Da), Molecular formula

B

Baseline: The detector signal when nothing but mobile phase is passing through. Peak areas are measured from the baseline, so a drifting or poorly drawn baseline changes the reported purity.See also: Peak area, Signal-to-noise ratio, Chromatogram
Batch: A quantity of material produced in one process or series of processes so that it is expected to be uniform. A test result applies to the batch only as far as the sample represents it.See also: Lot, Batch number, Lot release
Batch number: The code that identifies a batch and links a vial to its manufacturing and testing records. A certificate that names no batch number cannot be tied to any particular vial.See also: Batch, Lot, COA (certificate of analysis)
Bioburden: The number of living microorganisms on or in a material before it is sterilised. It is a manufacturing control measure, different from a sterility test on the finished product.See also: Sterility, Endotoxin
Blind sample: A sample sent to a laboratory without the information that could bias the analysis, such as the vendor or what result is hoped for. The lab sees only a code.See also: Sample code, Chain of custody, Anonymous purchase

C

C-terminus: The end of a peptide chain with the carboxyl group. Many synthetic peptides carry an amide here instead of a free acid, which changes the expected mass slightly.See also: N-terminus, Amidation, Sequence
Cake: The solid plug of freeze-dried powder at the bottom of a vial. Its look (intact, shrunken, collapsed or melted back) says something about how it was dried and stored, but nothing about identity or amount.See also: Lyophilised, Appearance test, Excipient
Calibration curve: A line built by running known amounts of a reference standard and plotting detector response against amount. A sample's response is read against the line to give its quantity.See also: Reference standard, Linearity, Assay, Peak area
CATO (certificate of authority to operate): The authority issued under RA 10657 by the Board of Chemistry together with the Professional Regulation Commission to chemical laboratories that meet the Board's requirements. It is a licensing step, separate from ISO/IEC 17025 accreditation.See also: RA 10657 (Chemistry Profession Act), Registered chemist, Accreditation
Certified reference material: A reference material whose property values come with a certificate stating their uncertainty and traceability, produced under a recognised standard for reference material producers. It sits at the top of the reference standard hierarchy.See also: Reference standard, Measurement uncertainty, Accreditation
Chain of custody: The documented record of who held a sample, when and in what condition, from the moment it was obtained to the moment it was tested. It is what lets a reader trust that the result belongs to the vial it is said to describe. Chain of custody explained in fullSee also: Blind sample, Sample code, Tamper-evident seal, Anonymous purchase
Charge state: The number of charges an ion carries in a mass spectrometer. The same peptide at different charge states shows up as a series of peaks at different m/z values, all pointing to one mass.See also: m/z, ESI (electrospray ionisation), Deconvolution
Chromatogram: The graph an HPLC run produces: detector response on the vertical axis against time on the horizontal axis. Each component shows up as a peak, and the peaks are what purity and amount are calculated from.See also: Peak, Retention time, Peak area, Baseline
Cleavage: The final synthesis step that releases the finished peptide from the resin and strips the side-chain protecting groups, usually with concentrated trifluoroacetic acid. It is the main reason crude peptides start out as TFA salts.See also: Trifluoroacetic acid (TFA), TFA salt, Crude peptide
Co-elution: Two or more components leaving the column at the same time so they appear as one peak. An impurity that co-elutes with the main peptide is counted as peptide, which makes HPLC purity look higher than it is.See also: Resolution, Specificity, LC-MS, HPLC purity
COA (certificate of analysis): A document reporting test results for a specific sample or batch, normally naming the laboratory, sample, methods, results, date and signatory. Its value depends on whether the sample it describes is the product in your hand and whether the document can be verified. COA (certificate of analysis) explained in fullSee also: Batch, Verification key, Registered chemist, Chain of custody
Coefficient of variation: The standard deviation of a set of results divided by their mean, usually given as a percentage. It is a common way to express precision and spread between batches.See also: Precision, Repeatability, Consistency
Cold chain: Keeping a product within its intended temperature range through shipping and storage. A test describes the vial as it was when sampled, not how it is handled afterwards.See also: Stability, Degradation product, Chain of custody
Column: The tube packed with fine particles where separation happens in HPLC. The particle chemistry, size and column length largely decide which impurities a method can tell apart from the main peptide.See also: Stationary phase, HPLC, Resolution
Consistency: The Tested Index component that measures how much a vendor's measured amount, as a share of label claim, varies between its passing batches. A vendor that is accurate on average but erratic batch to batch scores lower.See also: Coefficient of variation, Tested Index, Label claim
Consumer-submitted: A record for a sample sent in by a buyer, alone or as part of a group test. It is published but not scored, because the vial's handling before intake is outside Tested.ph's chain of custody.See also: Vendor-submitted, Group test, Anonymous purchase
Correction: A dated change to a published record or page, with the reason and what changed shown openly. Tested.ph lists every correction in its corrections log rather than editing silently.See also: Record, Right of reply
Counter-ion: A small charged molecule that pairs with the charged groups of a peptide in its solid salt form, such as trifluoroacetate, acetate or chloride. Counter-ions add weight to the powder without being peptide. Counter-ion explained in fullSee also: Salt form, TFA salt, Acetate salt, Hydrochloride salt, Net peptide content
Crude peptide: The product straight after cleavage and before purification. It holds the target peptide alongside deletion, truncated and other synthesis by-products.See also: Purification, Deletion sequence, Truncated sequence

D

Dalton (Da): The unit used for molecular masses, also called the unified atomic mass unit and defined from the mass of the carbon-12 atom. Peptide masses on certificates and in databases are normally given in daltons or grams per mole, which are numerically equivalent.See also: Monoisotopic mass, Average mass, Molecular formula
Data privacy: Handling personal information only for stated purposes and protecting it from misuse. Tested.ph records describe samples and vendors, not the people who buy or submit them, and its privacy notice follows RA 10173.See also: RA 10173 (Data Privacy Act of 2012), Group test, Consumer-submitted
Deamidation: Loss of the amide group from an asparagine or glutamine side chain, turning it into an acid. It happens during storage, especially with moisture and warmth, and adds a small mass shift that high-resolution mass spectrometry can detect.See also: Degradation product, Stability, HRMS, Aspartimide
Deconvolution: Software processing that combines the peaks from all charge states of a molecule into a single neutral mass. Certificates often report this deconvoluted mass rather than the raw m/z values.See also: Charge state, m/z, LC-MS
Degradation product: An impurity formed after manufacture as the peptide breaks down, for example through oxidation, deamidation or hydrolysis. Their levels can rise with time, heat, light and moisture.See also: Stability, Oxidation, Deamidation
Deletion sequence: An impurity that is the target peptide missing one or more amino acids, caused by a coupling step that did not complete during synthesis. It is usually close to the main peptide in both mass and retention time, which makes it one of the harder impurities to separate. Deletion sequence explained in fullSee also: Truncated sequence, Insertion sequence, Solid-phase peptide synthesis (SPPS), Co-elution
Detector: The part of an instrument that turns the separated components into a signal. In HPLC it is often a UV detector; in LC-MS a mass spectrometer acts as the detector and reports masses as well as timing.See also: UV detection, LC-MS, Chromatogram
Disulfide bond: A covalent link between the sulfur atoms of two cysteine residues that ties parts of a chain together, often into a ring. Forming one removes hydrogen atoms, so the expected mass depends on whether the bond is formed.See also: Oxidation, Monoisotopic mass, Sequence

E

Elemental impurities: Trace metals and other elements that can enter a product from catalysts, equipment or raw materials. The ICH Q3D guideline sets risk-based limits element by element.See also: Heavy metals, ICP-MS, ICH
Endotoxin: Lipopolysaccharide from the outer membrane of Gram-negative bacteria, which stays active after the bacteria are dead. It is the best-known cause of fever reactions from contaminated products, so it is tested separately from purity and sterility. Endotoxin explained in fullSee also: Endotoxin unit (EU), LAL (limulus amebocyte lysate), Recombinant factor C (rFC), Pyrogen, Sterility
Endotoxin unit (EU): The unit for endotoxin activity, defined against a reference standard endotoxin rather than by weight. Results are usually given in EU per millilitre or EU per milligram of product.See also: Endotoxin, LAL (limulus amebocyte lysate), Reference standard
ESI (electrospray ionisation): A gentle way of turning dissolved molecules into gas-phase ions by spraying them from a charged needle. Peptides usually pick up several protons, so one peptide appears at several m/z values, and ESI pairs naturally with liquid chromatography.See also: Charge state, LC-MS, Deconvolution, MALDI
Excipient: Any ingredient in a product other than the active substance, such as a bulking agent added to help a freeze-dried cake form. Excipients add to the gross weight of powder.See also: Gross weight, Cake, Net peptide content

F

FDA Philippines: The Food and Drug Administration of the Philippines, the regulator for health products including drugs, under the Department of Health. Its powers were strengthened by RA 9711.See also: RA 9711 (Food and Drug Administration Act of 2009), Product registration, Unregistered product
Fmoc chemistry: The most widely used SPPS method, named after the fluorenylmethyloxycarbonyl group that protects each incoming amino acid's amine. The group is removed with a mild base before the next amino acid is coupled.See also: Solid-phase peptide synthesis (SPPS), Protecting group, Aspartimide

G

GC (gas chromatography): Chromatography in which vaporised components are carried by a gas through a column. Headspace GC, which samples the vapour above a heated sample, is the standard method for residual solvents.See also: Residual solvents, HPLC
GMP: Good manufacturing practice: the regulated system of controls that makes sure medicines are consistently made and checked to their quality standards. A certificate of analysis from a GMP setting sits inside that system; one without it stands alone.See also: Lot release, Batch, COA (certificate of analysis)
Grade: The letter from A to F that the Tested Index gives a ranked vendor, based on its weighted score. The thresholds are published with the scoring method.See also: Tested Index, Scored batch, Insufficient data
Gradient elution: Running an HPLC method while the mobile phase composition changes over time, usually from mostly water to more organic solvent. It lets peptides and their closely related impurities elute one after another as separate peaks.See also: Mobile phase, RP-HPLC, Retention time
Gross weight: The total weight of powder in a vial or weighed for a test, including peptide, counter-ions, water and any excipients. A label amount can refer to gross weight or to peptide content, and the difference matters.See also: Net peptide content, Label claim, Excipient
Group test: Several buyers holding vials from the same batch sharing the cost of testing one sealed vial, with every member receiving the same record key. See group testing.See also: Consumer-submitted, Batch, Verification key

H

Half-life (scoring): In the Tested Index, the time after which a batch's weight in the score has halved. It describes how fast old results fade, and has nothing to do with how a compound behaves in the body.See also: Recency weighting, Tested Index
Hash: A short fixed-length value calculated from a file by a hash function. Changing even one character of the file gives a completely different value, which makes a hash a fingerprint for checking that a document is unchanged.See also: SHA-256, Record
Heavy metals: An older catch-all term for toxic metal contaminants such as lead, cadmium, mercury and arsenic. Modern guidance has replaced the old colour test with element-specific limits and instrumental methods such as ICP-MS.See also: Elemental impurities, ICP-MS
HPLC: High-performance liquid chromatography: a technique that pumps a dissolved sample through a packed column so its components separate and reach a detector at different times. It is the standard way to measure peptide purity and, against a reference standard, the amount of peptide in a sample.See also: HPLC purity, RP-HPLC, UHPLC, Chromatogram, Retention time
HPLC purity: The share of the total detected peak area that belongs to the main peptide peak in an HPLC chromatogram, reported as a percentage. It describes how clean the peptide material is relative to the impurities the method can see, not how much peptide is in the vial. HPLC purity explained in fullSee also: Area percent, Peak area, Net peptide content, Co-elution, Label claim
HRMS: High-resolution mass spectrometry: instruments such as Orbitrap or time-of-flight analysers that measure mass precisely enough to resolve individual isotope peaks. The result is usually reported with a mass error in parts per million.See also: ppm mass error, Monoisotopic mass, Isotope pattern
Hydrochloride salt: A peptide paired with chloride counter-ions, another common replacement for TFA. Chloride is a light counter-ion, so the salt form changes the peptide share of the powder.See also: Acetate salt, TFA salt, Counter-ion
Hygroscopic: Readily absorbing moisture from the air. Freeze-dried peptides are often hygroscopic, so an open or poorly sealed vial can gain water weight and degrade faster.See also: Water content, Lyophilised, Karl Fischer titration

I

ICH: The International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use, which publishes guidelines adopted by regulators worldwide. Its quality guidelines cover method validation, stability, impurities and manufacturing practice.See also: Method validation, Residual solvents, Elemental impurities, GMP
ICP-MS: Inductively coupled plasma mass spectrometry: a sample is broken into atoms in a hot plasma and the elements are counted by mass. It measures many elements at trace levels in one run and is the usual method for elemental impurities.See also: Elemental impurities, Heavy metals, Mass spectrometry
Identity test: A test that establishes whether the main molecule in a sample is the one named on the label, most often by measuring its mass and comparing it with the expected mass. Purity and amount figures mean little until identity is confirmed.See also: LC-MS, Monoisotopic mass, Retention time, MS/MS
ILAC: The International Laboratory Accreditation Cooperation, a network of accreditation bodies whose mutual recognition arrangement lets a laboratory accredited in one member economy be accepted in others.See also: Accreditation, PAB (Philippine Accreditation Bureau), ISO/IEC 17025
Impurity: Any component in a sample other than the intended substance. For peptides it covers synthesis by-products, degradation products, residual solvents, metals and other contaminants, each needing a suitable test to detect.See also: Related substances, Degradation product, Residual solvents, Elemental impurities
Insertion sequence: An impurity carrying an extra copy of an amino acid, for example when one was coupled twice. It is heavier than the target by the mass of the added residue.See also: Deletion sequence, Solid-phase peptide synthesis (SPPS), Monoisotopic mass
Insufficient data: The Tested Index status for a vendor without enough recent scored batches to rank. It is a statement about the evidence available, not a judgement of the vendor.See also: Tested Index, Scored batch, Grade
Intermediate precision: Precision within one laboratory when conditions vary, such as different days, analysts or instruments. It shows how much a result can move from run to run in normal use.See also: Precision, Repeatability, Reproducibility
Ion exchange: A process that swaps one counter-ion for another, for example replacing trifluoroacetate with acetate by passing the peptide through an ion-exchange resin or by repeated freeze drying from a dilute acid.See also: Salt form, TFA salt, Acetate salt
ISO/IEC 17025: The international standard for the competence, impartiality and consistent operation of testing and calibration laboratories. Laboratories are accredited against it for a defined list of tests, called the scope. ISO/IEC 17025 explained in fullSee also: Accreditation, PAB (Philippine Accreditation Bureau), ILAC
Isotope pattern: The cluster of closely spaced peaks a molecule produces because some of its atoms are heavier isotopes, mostly carbon-13. Its shape and spacing help confirm the charge state and the molecular formula.See also: Monoisotopic mass, HRMS, Charge state

K

Karl Fischer titration: A chemical method that measures water specifically, by reacting it with iodine and detecting the end point. It is the usual way to determine water content in peptide powders and reference standards. Karl Fischer titration explained in fullSee also: Water content, Hygroscopic, Mass balance

L

Label claim: The amount a product's label says it contains, such as the milligrams of peptide per vial. Assay results are often reported as a percentage of label claim, which only makes sense if it is clear whether the label means peptide or powder. Label claim explained in fullSee also: Assay, Overfill, Underfill, Gross weight
LAL (limulus amebocyte lysate): A reagent made from the blood cells of the horseshoe crab that clots or changes colour when it meets endotoxin. LAL tests in gel-clot, turbidimetric and chromogenic formats are the established pharmacopoeial endotoxin methods.See also: Endotoxin, Recombinant factor C (rFC), Endotoxin unit (EU)
LC-MS: Liquid chromatography coupled to mass spectrometry: the column separates the sample and a mass spectrometer measures the mass of what comes off at each moment. It links each chromatographic peak to a mass, so it can confirm the main peptide and help identify impurities. LC-MS explained in fullSee also: Mass spectrometry, ESI (electrospray ionisation), HPLC, Identity test, MS/MS
Linearity: A method's ability, within a given range, to give results directly proportional to the amount of substance. It is what lets a calibration curve be used to read off sample amounts.See also: Calibration curve, Range, Method validation
Lipidation: Attaching a fatty acid chain to a peptide, usually through a linker on a lysine side chain, as in semaglutide and tirzepatide. The attached chain is part of the expected structure, so it must be included in the expected mass.See also: PEGylation, Molecular formula, Monoisotopic mass
LOD (limit of detection): The smallest amount of a substance a method can reliably detect, though not necessarily measure with precision. Below it, "not detected" means only that the method could not see it.See also: LOQ (limit of quantitation), Signal-to-noise ratio, Method validation
LOQ (limit of quantitation): The smallest amount of a substance a method can measure with acceptable accuracy and precision. Results between the LOD and LOQ can show presence but not a reliable amount.See also: LOD (limit of detection), Range, Quantification
Lot: A defined quantity of product, often used interchangeably with batch; some manufacturers use lot for a portion of a batch, such as one filling run. Like a batch, it is identified by a code on the label.See also: Batch, Batch number, Lot release
Lot release: The formal decision in regulated manufacturing that a batch meets its specification and may be sold. Release testing is done on samples taken by the manufacturer, which is different from testing a vial bought on the open market.See also: Specification, GMP, Batch
Lyophilised: Freeze dried: frozen, then dried under vacuum so the ice turns straight to vapour. Most research peptides are sold lyophilised because the dry powder is far more stable than a solution. Lyophilised explained in fullSee also: Cake, Hygroscopic, Water content, Stability

M

m/z: Mass-to-charge ratio, the quantity a mass spectrometer actually measures, plotted along the horizontal axis of a mass spectrum. A peptide carrying several charges appears at a fraction of its mass, so m/z values must be converted before comparing with the expected mass.See also: Charge state, Deconvolution, Mass spectrometry
MALDI: Matrix-assisted laser desorption ionisation: the sample is mixed with a light-absorbing matrix, dried on a plate and hit with a laser pulse. Peptides mostly form singly charged ions, which makes spectra simple to read, and it is usually paired with a time-of-flight analyser.See also: ESI (electrospray ionisation), Mass spectrometry, m/z
Mass balance: Working out a substance's content by measuring everything else in the material, such as water, counter-ions, solvents and impurities, and subtracting it from the whole. Reference standard producers use it to assign a content value.See also: Net peptide content, Karl Fischer titration, Reference standard
Mass spectrometry: A family of techniques that turn molecules into charged ions and measure their mass-to-charge ratio. For peptides it is the main way to confirm identity, because the measured mass can be compared with the mass calculated from the expected sequence.See also: LC-MS, m/z, Monoisotopic mass, HRMS
Measurement uncertainty: The range within which the true value is expected to lie, given everything that can vary in a measurement. Two results that differ by less than their uncertainty may not truly differ.See also: Precision, Accuracy, Certified reference material
Method validation: Showing with experiments that an analytical method is fit for its intended purpose, by testing characteristics such as specificity, accuracy, precision, linearity and range. The international reference is the ICH Q2 guideline.See also: Specificity, Accuracy, Precision, Linearity, System suitability
Mobile phase: The liquid pumped through an HPLC column that carries the sample. For peptides it is usually water and acetonitrile with a small amount of acid such as trifluoroacetic acid or formic acid added.See also: Stationary phase, Gradient elution, Trifluoroacetic acid (TFA)
Molecular formula: The count of each type of atom in a molecule, written with element symbols. Expected masses are calculated from it, so a correct formula is the starting point for any identity check by mass.See also: Monoisotopic mass, Average mass, Sequence
Monocyte activation test (MAT): A pyrogen test that uses human immune cells in a dish to measure the signalling molecules they release when exposed to a sample. It responds to non-endotoxin pyrogens as well as endotoxin.See also: Pyrogen, Endotoxin, Recombinant factor C (rFC)
Monoisotopic mass: The mass of a molecule calculated using only the most abundant isotope of each element, such as carbon-12 and hydrogen-1. High-resolution instruments measure it directly, so it is the value to compare against when they report a peptide's mass. Monoisotopic mass explained in fullSee also: Average mass, Isotope pattern, HRMS, ppm mass error
MS/MS: Tandem mass spectrometry: a selected ion is broken into fragments and the fragments are measured. Because peptides tend to break along their backbone, the fragment masses can confirm the amino acid sequence, not just the total mass.See also: LC-MS, Peptide mapping, Sequence

N

N-terminus: The end of a peptide chain with a free amine group, where sequences are written from. It is a common site for deliberate modifications such as acetylation.See also: C-terminus, Acetylation, Sequence
Net peptide content: The percentage of a powder's total weight that is the peptide itself, after counter-ions, water and other non-peptide material are accounted for. It is measured separately from HPLC purity, usually by amino acid analysis or a mass balance. Net peptide content explained in fullSee also: Gross weight, Counter-ion, Amino acid analysis, HPLC purity, Mass balance

O

Out of specification (OOS): A result that falls outside the acceptance limits in the specification. In regulated manufacturing an OOS result triggers an investigation before any batch decision.See also: Specification, Lot release, Batch
Overfill: A measured amount above the label claim. Manufacturers sometimes add a deliberate margin; large or variable overfill still means the label is not accurate.See also: Label claim, Underfill, Assay
Oxidation: Addition of oxygen to susceptible residues, most commonly methionine, and also tryptophan and cysteine. It is a common degradation route, shows up as a mass increase and often as a new peak near the main one.See also: Degradation product, Stability, Disulfide bond

P

PAB (Philippine Accreditation Bureau): The national accreditation body of the Philippines, attached to the Department of Trade and Industry. It accredits testing and calibration laboratories against ISO/IEC 17025.See also: Accreditation, ISO/IEC 17025, ILAC
Peak: A rise and fall in a chromatogram or spectrum where a component reaches the detector. Its position identifies it relative to a standard and its area or height relates to how much of it there is.See also: Peak area, Retention time, Chromatogram
Peak area: The area under a peak in a chromatogram, worked out by the instrument software. It is proportional to the amount of that component reaching the detector, which is why purity uses area ratios and amount tests compare sample area against a reference standard. Peak area explained in fullSee also: Area percent, HPLC purity, Calibration curve, Baseline
PEGylation: Attaching chains of polyethylene glycol (PEG) to a peptide or protein. Because PEG chains vary in length, a PEGylated product shows a spread of masses rather than one sharp mass.See also: Lipidation, Average mass, Mass spectrometry
Peptide: A short chain of amino acids joined by peptide bonds. The line between a peptide and a protein is informal and based on length.See also: Amino acid, Peptide bond, Sequence
Peptide bond: The amide link that joins the carboxyl group of one amino acid to the amine group of the next, releasing water. It is the bond UV detectors see in HPLC and the bond MS/MS fragmentation usually breaks.See also: Peptide, UV detection, MS/MS
Peptide mapping: Cutting a peptide or protein into smaller pieces with an enzyme or chemical, separating the pieces and identifying each, usually by LC-MS. The resulting map confirms the sequence and can locate modifications such as oxidation.See also: MS/MS, LC-MS, Sequence
Ph. Eur.: The European Pharmacopoeia, published by the Council of Europe's EDQM. It sets quality standards for medicines across its member states and is often cited for endotoxin, sterility and other general methods.See also: Pharmacopoeia, USP
Pharmacopoeia: An official book of quality standards for medicines and their ingredients, setting tests, methods and limits. The best known are the United States Pharmacopeia and the European Pharmacopoeia.See also: USP, Ph. Eur., Specification
ppm mass error: The difference between a measured mass and the calculated mass, divided by the calculated mass and expressed in parts per million. It is how high-resolution results state how closely the observed molecule matches the expected one. ppm mass error explained in fullSee also: HRMS, Monoisotopic mass, Identity test
PRC: The Professional Regulation Commission, the Philippine agency that licenses professionals including chemists. A chemist's registration can be checked through its online verification service.See also: Registered chemist, RA 10657 (Chemistry Profession Act)
Precision: How closely repeated measurements of the same sample agree with each other. It is assessed at several levels: repeatability, intermediate precision and reproducibility.See also: Repeatability, Intermediate precision, Reproducibility, Accuracy
Product registration: Authorisation from FDA Philippines for a specific health product to be sold, recorded as a certificate of product registration. A registered product has been reviewed for that product, from that manufacturer, under that name.See also: FDA Philippines, Unregistered product, RA 9711 (Food and Drug Administration Act of 2009)
Protecting group: A temporary chemical cap on a reactive part of an amino acid that stops it reacting at the wrong time during synthesis. Protecting groups left on by mistake appear as impurities with a higher mass than the target.See also: Fmoc chemistry, Cleavage, Solid-phase peptide synthesis (SPPS)
Purification: Separating the target peptide from synthesis by-products, usually by preparative reversed-phase HPLC, keeping only the fractions that meet a purity limit. The pooled fractions are then freeze dried into powder.See also: Crude peptide, RP-HPLC, Lyophilised
Purity: How much of a sample is the intended substance relative to its impurities, always tied to a method. For peptides it almost always means HPLC area percent, which is a different quantity from net peptide content.See also: HPLC purity, Net peptide content, Impurity
Pyrogen: Any substance that can cause fever. Endotoxin is the most important, but non-endotoxin pyrogens exist, so an endotoxin test does not rule out every pyrogen.See also: Endotoxin, Monocyte activation test (MAT), LAL (limulus amebocyte lysate)
Pyroglutamate formation: Cyclisation of an N-terminal glutamine or glutamic acid into a ring, which loses a small neutral molecule and lowers the mass. It can occur during synthesis or storage.See also: N-terminus, Degradation product, Monoisotopic mass

Q

Quantification: Measuring an amount rather than just detecting presence. For peptides it normally means comparing the sample's HPLC peak area with that of a reference standard of known content.See also: Assay, Reference standard, LOQ (limit of quantitation)

R

RA 10173 (Data Privacy Act of 2012): The Philippine law that governs how personal information is collected and processed, and that created the National Privacy Commission. Information about a person's health is classed as sensitive personal information under the Act (RA 10173 on Lawphil).See also: Data privacy, Anonymous purchase
RA 10657 (Chemistry Profession Act): The Philippine law that regulates the practice of chemistry. It requires the head of a chemical laboratory to be a registered chemist, has chemistry reports signed with the chemist's registration number, and provides for a certificate of authority to operate for chemical laboratories (RA 10657 on Lawphil).See also: Registered chemist, CATO (certificate of authority to operate), PRC
RA 9711 (Food and Drug Administration Act of 2009): The Philippine law that strengthened the FDA. Among other things, it lists the sale or distribution of any health product that is adulterated, unregistered or misbranded as a prohibited act (RA 9711 on Lawphil).See also: FDA Philippines, Unregistered product, Product registration
Racemisation: Conversion of an amino acid from its natural L form to the D form, which can happen during synthesis. The product has exactly the same mass, so mass spectrometry alone cannot see it; chromatography or chiral analysis is needed.See also: Amino acid, Specificity, Related substances
Range: The interval between the lowest and highest amounts for which a method has been shown to be accurate, precise and linear. Results outside the validated range are less reliable.See also: Linearity, LOQ (limit of quantitation), Method validation
Recency weighting: Giving recent batches more influence on a vendor's score than older ones, so the Index reflects what a vendor sells now. Tested.ph uses an exponential weight defined by a half-life.See also: Half-life (scoring), Tested Index, Scored batch
Recombinant factor C (rFC): A lab-produced version of factor C, the endotoxin-sensing enzyme in horseshoe crab blood, used in a fluorescent endotoxin test. It detects endotoxin without harvesting crab blood and does not react to the glucans that can trigger some LAL reagents. Recombinant factor C (rFC) explained in fullSee also: LAL (limulus amebocyte lysate), Endotoxin, Monocyte activation test (MAT)
Record: The public page Tested.ph publishes for a tested sample, giving the task number, what was tested, by which method, the results, the signed report and its fingerprint. Records can be corrected, never silently changed.See also: Task number, Verification key, Correction, SHA-256
Reference standard: A well-characterised sample of the substance with an assigned content, used as the yardstick for identity, purity and amount measurements. Without a suitable standard, an HPLC run can give purity but not a trustworthy milligram figure. Reference standard explained in fullSee also: Certified reference material, Calibration curve, Assay, Retention time
Registered chemist: A person registered with the Board of Chemistry and the Professional Regulation Commission to practise chemistry in the Philippines. Under RA 10657, chemistry documents are official only when signed by a registered chemist with their registration number. Registered chemist explained in fullSee also: RA 10657 (Chemistry Profession Act), PRC, CATO (certificate of authority to operate), COA (certificate of analysis)
Related substances: Impurities that are chemically close to the target peptide, such as deletion sequences, oxidised forms and isomers. They are the impurities HPLC purity is designed to see.See also: Impurity, HPLC purity, Deletion sequence
Repeatability: Precision under the same conditions over a short time: same analyst, same instrument, same day. It is the tightest level of precision.See also: Precision, Intermediate precision, Reproducibility
Reproducibility: Precision between different laboratories running the same method. It is the main reason two labs can report slightly different figures for the same sample.See also: Precision, Intermediate precision, Measurement uncertainty
Residual solvents: Traces of organic solvents left over from synthesis and purification, such as acetonitrile or dichloromethane. The ICH Q3C guideline sorts solvents into classes by toxicity and sets limits for each.See also: GC (gas chromatography), Impurity, ICH
Residue: An amino acid as it sits inside a peptide chain, after losing the atoms of water that form the peptide bonds. Sequence positions and many impurity names, such as deletion of one residue, are counted in residues.See also: Amino acid, Sequence, Deletion sequence
Resolution: A measure of how completely two neighbouring peaks are separated in a chromatogram. Poor resolution between the main peak and an impurity means their areas cannot be measured independently.See also: Co-elution, System suitability, UHPLC
Retention time: The time between a sample entering the HPLC column and a component's peak reaching the detector. Matching the main peak's retention time to a reference standard run under the same conditions supports identity, but on its own it does not prove which molecule is present. Retention time explained in fullSee also: Chromatogram, Reference standard, LC-MS, Co-elution
Right of reply: A vendor's opportunity to respond to a record or vendor report before or after publication, with its reply shown alongside the facts. A reply is published, it does not change a result.See also: Correction, Vendor-submitted, Transparency score
RP-HPLC: Reversed-phase HPLC, the most common mode for peptides. The column surface is water-repelling and the mobile phase is a water and organic solvent mixture, so peptides separate by how hydrophobic they are and elute as the organic share rises.See also: HPLC, Stationary phase, Mobile phase, Gradient elution

S

Salt form: Which counter-ion a peptide is paired with in the solid, such as TFA, acetate or hydrochloride. The same peptide in different salt forms has different powder weights per milligram of peptide.See also: Counter-ion, TFA salt, Acetate salt, Ion exchange
Sample: The material actually tested, such as one sealed vial. Every result describes the sample; how far it speaks for other vials depends on how the sample was chosen and handled.See also: Batch, Chain of custody, Blind sample
Sample code: The neutral code that replaces a vial's identifying label before it goes to the laboratory. Tested.ph keeps the link between code and vendor, so the analyst does not know whose product it is.See also: Blind sample, Chain of custody, Task number
Scored batch: A batch whose record counts toward a vendor's Tested Index score: bought anonymously, published, within the scoring window and with complete identity, purity and amount results. A batch that fails identity is scored as zero.See also: Tested Index, Anonymous purchase, Insufficient data
Sequence: The order of amino acids in a peptide, written from the N-terminus to the C-terminus. Two peptides with the same amino acids in a different order can have the same mass, which is why some identity questions need MS/MS.See also: N-terminus, C-terminus, MS/MS, Molecular formula
SHA-256: A cryptographic hash function published by the US National Institute of Standards and Technology as part of the SHA-2 family. Tested.ph publishes the SHA-256 fingerprint of each signed report so anyone holding a copy can confirm it matches the original.See also: Hash, Record, Verification key
Signal-to-noise ratio: How tall a peak is compared with the random fluctuation of the baseline. It is one common way to set a method's limit of detection and limit of quantitation.See also: LOD (limit of detection), LOQ (limit of quantitation), Baseline
Solid-phase peptide synthesis (SPPS): The standard way to make synthetic peptides: the chain is built one amino acid at a time while anchored to insoluble resin beads, with excess reagents washed away after each step. Each step that does not go to completion leaves a characteristic impurity.See also: Fmoc chemistry, Protecting group, Cleavage, Deletion sequence, Crude peptide
Specification: The list of tests, methods and acceptance limits a material must meet to pass. A result is only a pass or fail against a stated specification.See also: Out of specification (OOS), Lot release, COA (certificate of analysis)
Specificity: A method's ability to measure the target unequivocally in the presence of other components likely to be there, such as impurities and degradation products. A purity method with poor specificity lets impurities hide under the main peak.See also: Co-elution, Method validation, Identity test
Stability: How well a substance keeps its identity, purity and amount over time under defined storage conditions. Stability studies show which degradation products appear and how fast.See also: Degradation product, Cold chain, Lyophilised
Stationary phase: The material fixed inside a chromatography column that sample components interact with. In reversed-phase peptide methods it is usually silica bonded with long hydrocarbon chains.See also: Mobile phase, Column, RP-HPLC
Sterility: The absence of living microorganisms. A sterility test incubates a sample in growth media and watches for growth; it says nothing about endotoxin, which can be present even when everything is dead.See also: Endotoxin, Bioburden, Pyrogen
System suitability: Checks run with each analytical sequence, usually on a standard, to confirm the instrument and method are performing properly that day, for example peak resolution, symmetry and the agreement of repeated runs of the standard. Results from a run that fails system suitability should not be reported.See also: Method validation, Resolution, Tailing factor

T

Tailing factor: A measure of how symmetrical a peak is, comparing its trailing edge with its leading edge. Strong tailing can hide small impurities after the main peak and is often checked as part of system suitability.See also: System suitability, Peak, Resolution
Tamper-evident seal: A seal or bag that cannot be opened without leaving visible damage, often with a unique number. It is used to show that a sample was not opened or swapped between stations.See also: Chain of custody, Sample code
Task number: The sequential number assigned to each Tested.ph record. Together with the verification key it opens the public record at /verify.See also: Verification key, Record, Sample code
Tested Index: Tested.ph's vendor rankings, built only from vials bought anonymously and calculated from published records with one fixed formula. Vendors cannot pay to change a score; the method is set out on the scoring method page.See also: Scored batch, Grade, Recency weighting, Transparency score, Anonymous purchase
TFA salt: A peptide paired with trifluoroacetate counter-ions, the form most synthetic peptides take straight after cleavage and purification. It is normal, but the trifluoroacetate adds weight that is not peptide. TFA salt explained in fullSee also: Trifluoroacetic acid (TFA), Counter-ion, Acetate salt, Ion exchange
Transparency score: The Tested Index component that reflects whether a vendor publishes batch-specific, verifiable reports, names its laboratory and answers right-of-reply requests. It carries the smallest weight of the score components.See also: Tested Index, Right of reply, COA (certificate of analysis)
Trifluoroacetic acid (TFA): A strong acid used to cleave peptides from synthesis resin and as an additive in HPLC mobile phases. Its anion, trifluoroacetate, often stays with the purified peptide as the counter-ion.See also: TFA salt, Cleavage, Mobile phase
Truncated sequence: An impurity where chain growth stopped early, leaving a shorter peptide missing residues from one end. Synthesis often caps failed chains on purpose so they end up as truncated sequences that are easier to remove.See also: Deletion sequence, Acetylation, Crude peptide

U

UHPLC: Ultra-high-performance liquid chromatography: HPLC run with smaller column particles at higher pressures. It gives sharper peaks and shorter runs, which can separate impurities that a conventional HPLC method would merge with the main peak.See also: HPLC, Resolution, Co-elution
Underfill: A measured amount below the label claim, also called an underdosed vial in buyer forums. It can come from filling errors, counting powder weight as peptide, or degradation.See also: Label claim, Overfill, Net peptide content
Unregistered product: A health product sold without FDA Philippines registration. A laboratory result about a sample does not make a product registered or approved for any use.See also: Product registration, FDA Philippines, RA 9711 (Food and Drug Administration Act of 2009)
USP: The United States Pharmacopeia, a standards-setting organisation that publishes monographs and general chapters on testing medicines, along with reference standards. Its general chapters are widely used as method references outside the US.See also: Pharmacopoeia, Ph. Eur., Reference standard
UV detection: Measuring how much ultraviolet light the column output absorbs as it passes a detector. Peptide bonds absorb in the far ultraviolet, so a UV detector sees the target peptide and most peptide-related impurities, but not water or most counter-ions.See also: HPLC, Detector, Chromatogram

V

Vendor-submitted: A record for a sample the vendor sent in itself. It is published with that label but never counts toward a score, because the vendor chose the vial.See also: Anonymous purchase, Consumer-submitted, Tested Index
Verification key: A short code printed with a task number that unlocks the matching public record. Keys use a character set without I, L, O or U so they cannot be confused with numbers.See also: Task number, Record, SHA-256

W

Water content: How much water a powder holds, reported as a percentage of its weight. In peptides it lowers the peptide share of the powder and can speed some degradation routes.See also: Karl Fischer titration, Hygroscopic, Net peptide content