Purity Analysis: What the Numbers Mean
Understanding peptide purity specifications — what 95%, 98%, and 99% purity actually mean for your research.
Scientific background / literature overview only. Discussion of published research does not describe the intended use of Novex Peptide products.
Introduction
When a peptide is described as "95% pure" or "99% pure," this refers to the percentage of the total sample that consists of the target peptide, as determined by analytical HPLC. Understanding what these numbers mean — and what they do not mean — is essential for interpreting experimental results.
How Purity Is Measured
HPLC Purity
Purity is determined by reverse-phase HPLC with UV detection at 214 nm. The area of the main peak is expressed as a percentage of the total area of all detected peaks.
What Purity Does Not Measure
Purity Grades and Their Applications
≥90% Purity
Suitable for:
≥95% Purity
Suitable for:
≥98% Purity
Suitable for:
≥99% Purity
Suitable for:
Impurities and Their Sources
Deletion Sequences
Truncated peptides resulting from incomplete amino acid coupling during SPPS. These are the most common impurity.
Diastereomers
Peptides with incorrect stereochemistry at one or more amino acid centres, resulting from epimerisation during synthesis.
Oxidation Products
Modified forms of the peptide, typically involving methionine sulfoxide or cysteine disulphide formation.
Adducts
Peptides with attached molecules such as TFA (from the HPLC mobile phase) or water.
Choosing the Right Purity Grade
Select the purity grade appropriate for your research application. Higher purity is not always necessary and increases cost. For most in vitro research, ≥95% purity is sufficient.
Research Limitations
Purity analysis is a chemical measurement. It does not confirm biological activity, solubility, or suitability for any specific research application. All products are for research use only.
References
- 1.Snyder LR, Kirkland JJ. Introduction to Modern Liquid Chromatography. 3rd ed. Wiley; 2010.
- 2.European Pharmacopoeia. 2.2.29. Liquid Chromatography.
- 3.Bachem. Purity Determination of Peptides by HPLC. Technical Notes. 2019.
Research use only. This article is for educational purposes only and does not constitute advice for any application involving human use. No medical claims are made.
