Research Peptide Glossary: Common Laboratory and Product Terms

This glossary provides definitions of common terms encountered in research peptide catalogues, analytical documentation, and laboratory records. Each entry is written as an accessible reference, with links to more detailed articles where a term is covered in greater depth.

This glossary is for informational and educational purposes only. It does not provide medical advice, and it does not discuss human use of any product.

Amino Acid

An organic compound containing both an amino group (−NH₂) and a carboxyl group (−COOH). Amino acids are the fundamental building blocks of peptides and proteins. There are twenty standard amino acids encoded by the genetic code, each with a characteristic side chain that determines its chemical properties. In a peptide, amino acids are joined by peptide bonds to form a specific sequence, which defines the peptide’s identity.

Analytical Method

A defined procedure for measuring or characterising a chemical substance. In research peptide analysis, the most common analytical methods are High-Performance Liquid Chromatography (HPLC) for purity assessment and mass spectrometry (MS) for identity confirmation. Each analytical method has specific capabilities and limitations; different methods answer different questions about a sample. See HPLC Testing Explained and Mass Spectrometry Testing Explained.

Batch

A specific quantity of a product manufactured under uniform conditions during a single production run. Every vial from the same batch shares the same manufacturing conditions and the same batch number. Analytical documentation (Certificate of Analysis) is typically issued per batch, meaning all vials from that batch share the same analytical data. Batch traceability is an essential component of laboratory record keeping.

Certificate of Analysis (COA)

A document, typically issued by the testing laboratory or the supplier, that reports the results of analytical testing performed on a specific batch. A peptide COA commonly includes HPLC purity data, mass spectrometry identity data, the batch number, the product name, and the test date. For a detailed guide, see How to Read a Peptide Certificate of Analysis.

Chromatogram

A graphical representation of detector response (y-axis) plotted against time (x-axis), produced during a chromatographic analysis such as HPLC. Each peak in the chromatogram corresponds to a component that eluted from the column and was detected. The main peak represents the target compound, and smaller peaks represent other detectable components. The area under each peak is used to calculate the relative proportion of each component.

HPLC (High-Performance Liquid Chromatography)

An analytical technique that separates components of a liquid mixture by passing them through a column packed with a stationary phase under high pressure. Different compounds interact differently with the stationary phase and therefore travel through the column at different speeds, emerging (eluting) at different times. In research peptide analysis, HPLC is primarily used to estimate purity. For a full explanation, see HPLC Testing Explained.

Identity

In analytical chemistry, identity refers to the confirmation that a substance is what it is claimed to be. For research peptides, identity is typically confirmed by mass spectrometry: the measured molecular mass of the sample is compared against the theoretical mass calculated from the amino acid sequence. Identity is distinct from purity — a sample can be confirmed as the correct peptide (by MS) while containing impurities (by HPLC), or it could appear pure (by HPLC) but be a different molecule altogether (identity not confirmed).

Lot Number

See Batch. The terms “lot number” and “batch number” are synonymous in research peptide documentation.

Lyophilised (Freeze-Dried)

A substance that has undergone lyophilisation — a dehydration process in which the material is frozen and then subjected to vacuum, causing the frozen water to sublimate (transition directly from solid to gas). Lyophilised peptides are supplied as a dry powder or solid “cake.” The appearance of lyophilised material can vary between products and batches without indicating any quality difference. See Lyophilised Research Products Explained.

Mass Spectrometry (MS)

An analytical technique that measures the mass-to-charge ratio (m/z) of ionised molecules. In research peptide analysis, MS is used to determine the molecular mass of a sample and thereby confirm its identity by comparison with the theoretical mass calculated from the amino acid sequence. MS answers the question “what is it?” and complements HPLC, which answers “how pure is it?”. See Mass Spectrometry Testing Explained.

Molecular Mass (Molecular Weight)

The mass of a molecule, typically expressed in Daltons (Da). One Dalton is defined as one-twelfth of the mass of a carbon-12 atom. The theoretical molecular mass of a peptide can be calculated by summing the masses of its constituent amino acids and accounting for the loss of water molecules during peptide bond formation. The measured molecular mass (determined by mass spectrometry) should closely match the theoretical value for identity to be confirmed.

Peak

In a chromatogram or mass spectrum, a peak is a localised increase in detector signal corresponding to the detection of a component. In HPLC, the main peak represents the target compound and its area is used to calculate purity. In mass spectrometry, the molecular ion peak represents the signal from the intact peptide ion and is used to determine the measured molecular mass.

Peptide

A molecule consisting of two or more amino acids linked by peptide bonds. Peptides are distinguished from proteins primarily by size, though there is no universally agreed boundary. A peptide’s identity is defined by its amino acid sequence. For a fuller introduction, see Research Peptides Australia: A Guide to Terminology and Documentation.

Purity

In research peptide analysis, purity is an estimate of the proportion of a sample that corresponds to the target peptide relative to other detectable components. It is typically determined by HPLC and reported as a percentage (e.g., 98% purity means 98% of the total detected peak area is attributable to the main peak). Purity is relative to what the detector can detect and does not confirm identity. See HPLC Testing Explained.

Research Use Only

A regulatory designation indicating that a product has not been evaluated or approved for human therapeutic or diagnostic use by relevant regulatory authorities (such as the Therapeutic Goods Administration in Australia). Products labelled for research use only are supplied for laboratory investigation purposes. The designation describes the regulatory framework governing the product’s supply, not its quality or purity.

Retention Time

In HPLC, the time elapsed between sample injection and the appearance of a peak maximum at the detector. Under consistent analytical conditions, a given compound has a characteristic retention time. Retention time can support — but does not by itself confirm — identity. Two different compounds may have similar retention times under the same conditions.

Sample

In analytical chemistry, a sample is a portion of material drawn from a larger quantity (such as a production batch) for the purpose of testing. The analytical results reported on a Certificate of Analysis refer to the tested sample; it is assumed (based on batch uniformity) that the results are representative of the entire batch.

Sequence (Amino Acid Sequence)

The specific linear order of amino acids in a peptide, typically written using standard single-letter or three-letter amino acid codes from the N-terminus (amino end) to the C-terminus (carboxyl end). The sequence is the most fundamental identifier of a peptide: two peptides with different sequences are different molecules, regardless of any similarity in their names. The molecular mass of a peptide is calculated from its sequence.

References and Further Reading

• IUPAC. Compendium of Chemical Terminology (Gold Book). International Union of Pure and Applied Chemistry.
• Moss, G.P., Smith, P.A.S., & Tavernier, D. (1995). “Glossary of class names of organic compounds and reactive intermediates based on structure.” Pure and Applied Chemistry, 67(8–9), 1307–1375.
• Therapeutic Goods Administration (TGA). Regulation of therapeutic goods in Australia. Australian Government Department of Health and Aged Care.
• Research Peptides Australia: A Guide — broader introduction to research peptide terminology.
• Peptide Reconstitution Calculator — a laboratory tool for calculating solution concentration and draw volumes.