Research-material documentation has its own vocabulary, and a Certificate of Analysis can be hard to read without it. This glossary defines the terms that appear most often — grouped into analytical methods, peptide chemistry and identity, documentation and quality, and storage and handling. The definitions are plain-language working explanations to support documentation literacy; they are not statements about any use of the materials, and where a formal standard exists, that source governs.

Analytical Methods

RP-HPLC (reverse-phase high-performance liquid chromatography)
A separation technique that resolves the components of a sample by passing it through a column under a solvent gradient; commonly used to report peptide purity as an area-percent value.
LC-MS (liquid chromatography–mass spectrometry)
Liquid chromatography coupled to a mass spectrometer; used to confirm identity by measuring molecular mass and comparing it to the value calculated from the sequence.
Area percent
A purity expression: the proportion of the total integrated detector signal attributable to the target peak, for the tested sample under the stated method.
Retention time
The time a component takes to travel through a chromatography column under set conditions; a reproducible retention time helps characterize a peak.
Monoisotopic mass
A molecule's mass calculated using the most abundant isotope of each element; typically reported by high-resolution mass spectrometry.
Average mass
A molecule's mass calculated using the average natural isotopic abundance of each element; differs from monoisotopic mass, more so for larger molecules.
Charge state
The number of charges a molecule carries during mass-spectrometry ionization; one molecule can appear at several charge states, which are combined to derive its mass.
Mass tolerance
The permitted difference between an observed and a theoretical mass for the two to be considered a match; depends on the instrument and calibration.
Orthogonal methods
Two analytical approaches that probe different properties (for example, chromatographic behavior and molecular mass), providing independent lines of confirmation.

Peptide Chemistry & Identity

Peptide
A chain of amino-acid residues linked by peptide bonds; shorter than a protein.
Residue
A single amino-acid unit within a peptide chain.
Sequence
The ordered list of residues that defines a peptide; the basis for calculating its theoretical mass.
Synthetic peptide
A peptide assembled chemically to a defined sequence, rather than isolated from a biological source; reproducible from lot to lot.
Solid-phase peptide synthesis (SPPS)
A common method of assembling a peptide one residue at a time on a solid support, then cleaving and purifying it.
Analogue
A peptide whose sequence is based on, but modified from, a reference peptide.
Fragment
A peptide corresponding to part of a larger parent protein or peptide sequence.
Molecular formula
The count of each element in a molecule (for example, C, H, N, O, S), from which mass is derived.
CAS number
A unique registry identifier assigned to a chemical substance by the Chemical Abstracts Service.
Net peptide content
The fraction of a sample's total mass that is actually peptide, as distinct from associated water and counterions; different from purity.
Counterion
An ion associated with the peptide (often from the acid used in purification) that contributes to total mass without being peptide.

Documentation & Quality

Certificate of Analysis (COA)
The analytical record for a specific lot, documenting which tests were performed, by what methods, and with what results.
Lot (or batch) number
The unique identifier tying a physical material to its production and testing records; it appears on the container and the documentation.
Traceability
The ability to connect a material to its records — COA, supporting reports, order, and inventory — through a consistent identifier.
Independent third-party verification
Analytical testing performed by a laboratory separate from the supplier, reviewed alongside the supplier's own COA.
ISO/IEC 17025
An international standard for the competence of testing and calibration laboratories; an accreditation many independent labs operate under.
Reporting limit
The smallest amount a method can reliably report; a result of "not detected" is bounded by this limit, not proof of total absence.
Related substances
Species other than the target that a method detects — for peptides, often synthesis-related; their presence is reflected in a purity figure.
Retest date
A date or condition after which a material is re-evaluated rather than relied upon by default.

Storage & Handling

Lyophilized powder
A freeze-dried solid; the stable reference form in which research peptides are typically supplied.
Lyophilization (freeze-drying)
Removal of water from a frozen material by sublimation under reduced pressure, yielding a dry solid.
Reconstitution
Returning a lyophilized material to solution by adding an appropriate aqueous solvent.
Aliquot
A single-use portion divided from a reconstituted stock to limit repeated freeze–thaw cycling.
Freeze–thaw cycle
One round of freezing and thawing a solution; repeated cycles are commonly minimized to preserve a consistent reference.
Cold chain
The continuity of temperature control from dispatch to the receiving laboratory's storage.
Hygroscopic
Tending to absorb moisture from the air; relevant to how some materials are handled and stored.

A Note on Scope

These definitions are educational and documentation-focused. They describe analytical, chemical, and handling concepts only — not effects, uses, or suitability of any material. All products referenced across the Prototides catalog are supplied for laboratory research use only, and suitability for a given research workflow is determined by the investigating laboratory against its own requirements and SOPs.