How to Read an HPLC / MS Lab Report — and Get Reconstitution Maths Right

A lab report is only useful if you know what each number measures. This guide walks through the results on a typical peptide report, then shows how to use them when preparing stock solutions.

HPLC purity

Reverse-phase HPLC separates the peptide from synthesis by-products such as truncated or deletion sequences. Purity is reported as the main peak's share of the total peak area at the detection wavelength (usually 214–220 nm).

• Area % is relative: it describes UV-absorbing species only, not water, salts or counter-ions.
• Method matters: the column, gradient and wavelength should be stated, since different methods can resolve different impurities.
• Purity is not content: a 99% pure peptide can still be only 70–85% peptide by weight once water and counter-ions are counted.

Mass spectrometry identity

Electrospray mass spectrometry confirms that the main component has the expected molecular mass. Reports compare the observed mass with the theoretical value; agreement within about ±1 Da is typical for peptides of this size. Larger peptides often appear as multiply charged ions ([M+2H]²⁺, [M+3H]³⁺), which are deconvoluted to give the neutral mass.

Measured mass per vial

Gravimetric or quantitative assays report how much material is actually in the vial, compared with the label claim. A result of 10.1 mg on a 10 mg vial is 101% of claim. This is the number to use in concentration calculations when it is available.

Endotoxin and elemental impurities

• Bacterial endotoxin (USP <85>, LAL method) is reported in EU/mg. It matters most for cell-based work, where endotoxin activates immune pathways and confounds results.
• Elemental impurities (USP <232>) cover lead, arsenic, cadmium and mercury, reported in ppm against a limit.
• A test that was not performed simply does not appear on our reports — absence is never shown as a pass.

Reconstitution maths

Concentration (mg/mL) = peptide mass (mg) ÷ diluent volume (mL). Adding 2.0 mL of diluent to a 10 mg vial gives 5.0 mg/mL, so a 100 µL aliquot contains 0.5 mg.

• Use the measured mass when the report gives one: 10.1 mg in 2.0 mL is 5.05 mg/mL, not 5.00.
• For molar work, correct for net peptide content: 10 mg at 80% net content contains 8 mg of peptide.
• Molarity = (mg/mL ÷ molecular weight in g/mol) × 1000 gives mmol/L.
• Label every vial with the concentration, date and lot number so results can be traced back to the report.

Verifying a report

Every BELIGAS lab report carries a task number and a unique verification key. Enter the key at the Verify page — or scan the report's QR code — to open the published report for that lot and confirm the values match.