Quantification of Free Sialic Acid in Human Plasma Through a Robust Quinoxalinone Derivatization and LC-MS/MS Using Isotope-Labeled Standard Calibration

Document Type


Publication Date



We report an accurate quantification of free sialic acid (SA) in human plasma using LC-MS/MS method with isotope-labeled standard calibration (ILSC) and robust derivatization. Specifically, derivatization of SA with a stable and inexpensive 3,4-diaminotoluene (DAT) provides a stable product of SA with high MS response, proving a convenient and cost-effective LC-MS/MS analysis of free SA. In addition, the use of (13)C3-SA as calibration standard ensured the accuracy for the measurement. This assay used ultra high performance liquid chromatography (UHPLC) for separation of native/labeled SA and IS from matrix interference, and employed mass spectrometry in multiple reaction monitoring (MRM) mode for sensitive and selective detection. We have achieved a lower limit of quantification (LLOQ) of 20ng/mL and a total running time of 4.2min, which is the most sensitive and quick measurement for free SA in biomatrices.


Wang D, Zhou X, Wang L, Wang S, Sun X-L. Quantification of free sialic acid in human plasma through a robust quinoxalinone derivatization and LC-MS/MS using isotope-labeled standard calibration. 2014;944:75–81. Available from: https://pubmed.ncbi.nlm.nih.gov/24291723