Stability of retention times and peak areas are crucial for the evaluation of peptide mapping experiments especially in LC-UV type experiments e.g. in process control or stability studies. In this study we demonstrated that the Vanquish UHPLC system provided extraordinary stability of retention time, peak area and peak capacity of a very large sample set of 86 injections over more than 80 hours. This stability will enable the analysts to confidently attribute a change in retention time or peak area to a real peptide modification and avoids any misinterpretation of the data.