It is very important to understand the difference between the net content of peptides and the total weight (gross weight) of peptides. The weight of dried peptides does not only include peptides,It also contains some non peptide components, such as water, absorbed solvents, coordination ions, and salts. The net content of peptides refers to the weight percentage of peptides in it,The numerical range of this percentage is large, possibly from 50% to 90%, depending on purity, sequence, and synthesis and purification methods,Do not confuse the net content of peptides with the purity of peptides, they are completely different concepts. Purity is usually determined by HPLC.Purity is defined as the percentage of components containing the correct sequence in a peptide sample, while the net content of a peptide refers to the percentage of peptide substances relative to non peptide substances in the sample,The net content of peptides is usually determined by amino acid composition analysis or UV spectrophotometry. This information is mainly important for calculating the concentration of peptides in experiments that are sensitive to their concentration.