What is the difference between Net Peptide Weight and Gross Peptide Weight?

It is important to understand the difference between net weight and gross weight. The dry peptide powder shipped to you usually contains not only peptides but also some other substances such as water, absorbed solvents, counterions, and salts. The Gross Peptide Weight refers to the weight of this mixture. Net Peptide Weight indicates the actual weight of the peptide component of your sample. Net peptide content is usually 50-80% of the gross peptide weight and is usually determined by amino acid analysis or Nirtongen analysis. Net peptide content should not be confused with purity. Purity defines the percentage of the target peptide sequence in the peptide component of your sample. However, net peptide content is the percentage of peptide components in your sample.