With an increasing number of peptide-based drugs being developed and used in the market, reliable, rapid and sensitive quantitation methods are needed. Although traditional immunoassay based methods can offer sensitive quantitation for larger molecules, they have poor linear dynamic range and utilize antibodies which can detect only a single, specific target, making assays costly and time consuming. With high selectivity, improved precision and accuracy, the LC-MS/MS technique is favored in peptide quantitation.