LC-MS/MS platform enable simultaneous relative and absolute quantification of multiple metabolites in a biological system. The results are widely used for biomarker discovery by investigating the relative changes in metabolite concentrations. The resulting data have been widely used to for biomarker discovery. By providing the exact molecular weights and retention time, LC-MS/MS techniques serves as a powerful analytical tool for identification and quantification of small molecules (metabolites). Creative Proteomics has established sensitive, reliable, and accurate HPLC-MS/MS method for quantification of metabolites in pentose phosphate pathway metabolites.