The amount of desired product in a sample is determined, based on gross weight and analytical HPLC purity.
Peptide purity is the amount of correct peptide relative to all analytes that absorb at 214 nm, most likely deletion, truncation or incompletely deprotected sequences, etc. Peptide purity is determined by HPLC analysis with detection at 214 nm, where the peptide bond absorbs. Peptide purity does not take into account water and salts that are usually present in the sample.
Peptide content is the percentage of total peptides present in the product relative to everything else present in the sample, such as water, salts, etc. Peptide content is determined by "Amino Acid Analysis" or AAA.
The absolute amount of correct peptide in a sample is the product of the peptide content and the peptide purity.