The MassPREP™ Phosphopeptide Kit contains one piece of 186002325 MassPREP™ Enolase Digest and one piece of 186003285 MassPREP™ Phosphopeptide Standard Enolase which contains 4 Yeast Enolase derived phosphorylated peptides; T18p, T19p, T43p, T43pp. This kit allows maximum flexibility for mixing a complex sample spiked with a known mixture of phospotylated peptides to help optimize phosphopeptide detection in LC/MS, LC/UV and MALDI-MS analyses. Using this standard, scientists have greater control over sample preparation, with the option to use pure peptides or to define phosphopeptide to unmodified peptide ratio.