Analytical Methods Glossary5

High-Performance Liquid Chromatography (HPLC) is the primary analytical technique used to measure peptide purity. A sample is introduced into a mobile phase flowing under high pressure through a column packed with stationary-phase particles. Each component in the mixture interacts differently with the stationary phase and elutes at a characteristic retention time. A UV detector — typically set to 220 nm for peptides — records a signal proportional to concentration, producing a chromatogram. Purity is calculated as the peak area of the target compound divided by the total peak area, expressed as a percentage. For research peptides, reverse-phase HPLC (RP-HPLC) is standard: the nonpolar stationary phase separates compounds by hydrophobicity. HPLC is fast, highly reproducible, and sensitive to low-percentage impurities — including truncation fragments, oxidation products, and synthesis byproducts. HPLC purity appears on every Certificate of Analysis (COA) as the headline analytical metric. It is complemented by LC-MS, which confirms molecular identity rather than purity percentage.

Liquid Chromatography–Mass Spectrometry (LC-MS) combines the separation power of liquid chromatography with mass spectrometric detection to confirm compound identity at the molecular level. Where HPLC measures relative peak areas to calculate purity percentages, LC-MS measures the mass-to-charge ratio (m/z) of ionized molecules to verify that the compound in the vial is actually the stated peptide. The technique can identify individual components in a complex mixture at very low concentrations, and can detect synthesis byproducts, truncation fragments, oxidation products, and sequence errors that HPLC alone cannot distinguish from the target compound. On a Certificate of Analysis, LC-MS results typically appear as an observed molecular weight compared against the theoretical mass of the stated peptide. Agreement within instrument accuracy (typically ±0.1–1.0 Da depending on the mass analyzer) constitutes identity confirmation. The combination of HPLC purity percentage and LC-MS identity confirmation on the same COA is the standard dual-assay benchmark for research peptide quality characterization.

A Certificate of Analysis (COA) is a laboratory document that records the analytical results for a specific batch of a research compound. For research peptides, a COA typically includes: the compound name, lot or batch number, the testing laboratory's name, date of analysis, methods used (HPLC for purity, LC-MS for identity), and the numerical results for each assay. HPLC purity is reported as a percentage; mass spectrometry results are reported as observed versus theoretical molecular weight. The COA is lot-specific — it represents a single production batch, not a blanket product-level quality assertion. When evaluating a COA, key checks include: (1) the compound name and batch number match the product in hand; (2) HPLC purity meets the threshold required for the research application; (3) LC-MS observed mass matches the theoretical mass of the stated sequence; and (4) the testing date is recent relative to the batch. Some COAs include additional assays — endotoxin (LAL), residual solvent, heavy metals — though these are not standard for all research peptide batches. Lot-specific COA availability is the standard documentation model for research-use-only compounds.

Lyophilization (freeze-drying) is a dehydration process used to preserve labile compounds — including research peptides — by removing water under vacuum while the sample remains frozen. The process occurs in three stages: freezing the sample; primary drying, in which vacuum is applied to sublime frozen water crystals directly from solid to vapor without passing through liquid phase; and secondary drying to remove residual bound water adsorbed to the compound. For research peptides, lyophilization produces a stable dry powder with substantially extended shelf life compared to solution-phase material. The dry powder form is resistant to the hydrolysis and microbial degradation that degrade peptide solutions over time. Lyophilized peptides are typically stored at −20 °C or 4 °C and are stable for months to years depending on the compound and storage conditions. The white-to-off-white powder appearance is the standard supply form for virtually all research peptides.

Research Use Only (RUO) is a designation applied to chemical and biological compounds — including synthetic peptides — that are intended exclusively for laboratory and scientific research purposes. RUO products are not intended for diagnostic, therapeutic, clinical, or consumer use, and are not evaluated or approved by regulatory agencies for any in-human application. The designation establishes that the supplier has no role in clinical or consumer product chains, and that appropriate oversight — institutional review, safety protocols, regulatory compliance — for any research application is the researcher's responsibility. RUO is distinct from terms such as investigational, clinical-grade, or pharmaceutical-grade. For research peptides, RUO means the products are supplied solely for use in laboratory settings, such as analytical studies and in vitro research. The designation is not a quality grade — it specifies intended use context, not purity or analytical specifications. Phase 1 Peptides supplies all products strictly as research-use-only materials and makes no representations about human or veterinary applications.