Laboratory glossary
Laboratory and quality-control glossary
Twenty-four laboratory and quality-control terms, explained through the distinctions that matter when reading a compound page or certificate.
Learn what separates a specification from a result, purity from identity, and an aliquot from a dilution. Each entry includes context and a common misunderstanding.
Containers and preparation
Identify the material, container and preparation step before comparing quantities or handling conditions.
- Vial — A primary glass container with a crimped septum closure used to supply a compound, commonly in lyophilized form under an inert atmosphere.
- Septum — The puncturable portion of a vial’s elastomer stopper, secured beneath a crimped closure, which permits needle access and reseals after withdrawal.
- Aliquot — A measured portion separated from a stock solution at the same concentration, intended for a single use without reopening the entire stock.
- Lyophilizate — A porous solid remaining after water is removed from a frozen solution by sublimation; a form used to preserve and ship research compounds.
- Reconstitution — The operation of returning a lyophilized solid to solution by adding a compatible diluent inside its vial through the septum.
- Diluent — A liquid added to dissolve a lyophilized solid or reduce the concentration of an existing solution; it contributes to the final volume.
- Bacteriostatic water — Sterile water containing a bacteriostatic preservative, commonly 0.9% benzyl alcohol, to inhibit bacterial multiplication in repeated-access contexts.
Analytical results and traceability
Distinguish a test result from an acceptance criterion and keep identity, purity and batch documentation separate.
- HPLC — A liquid-phase separation technique used to assess a batch’s chromatographic purity through the relative area of its principal peak.
- Chromatographic purity — The percentage of total integrated chromatographic peak area assigned to the main peak under the stated analytical conditions.
- ESI-MS — An analytical technique measuring ions’ mass-to-charge ratios to assess whether a compound’s mass is consistent with its declared structure.
- Identity — Testing that assesses whether the substance in the vial corresponds to its declared identity, rather than how dominant it is in a mixture.
- Certificate of analysis — A document reporting analytical determinations performed on a specifically identified material batch, rather than on a compound in general.
- Specification — An acceptance criterion established before analysis: the threshold a batch must meet for release, rather than the measured result.
- Batch — A defined quantity of material produced and processed as one homogeneous unit, carrying its own identifier and corresponding analytical documentation.
- Sterile — Absence of viable microorganisms in a particular article, achieved through a validated process; a state of that article, not an intrinsic compound property.
- Research use only — Research use only: a statement that this material is supplied for laboratory work, not diagnostic use or administration to humans or animals.
Molecular descriptions and material behavior
Understand the molecular description and the physical changes that can affect how a sample is interpreted or handled.
- Peptide — A chain of amino acid residues joined by peptide bonds; its sequence and modifications, rather than its commercial name, define its identity.
- Amino acid sequence — The order of residues in a peptide from N-terminus to C-terminus, written in one-letter code, such as GHK, or three-letter code, Gly-His-Lys.
- Peptide fragment — A continuous segment of a larger peptide chain, synthesized as a separate material and named using its positions in the parent sequence.
- Analog — A structurally modified relative of a reference molecule, retaining a recognizable framework but representing a distinct compound.
- Molecular weight — The mass of a molecule calculated from its composition, often reported in daltons; the corresponding molar mass is expressed in grams per mole.
- CAS number — A numerical identifier assigned by Chemical Abstracts Service to a registered chemical substance, independently of commercial naming.
- Hygroscopic — A hygroscopic material takes up and retains atmospheric moisture; a cold vial should equilibrate while closed before its contents are accessed.
- Aggregation — Association of peptide molecules with one another rather than remaining individually dispersed in solvent, forming soluble or insoluble aggregates.