Development of quantitative method for determination of γ-glutamyl peptides by capillary electrophoresis tandem mass spectrometry: An efficient approach avoiding matrix effect

Serum gamma-glutamyl di- and tripeptides have proven to be useful biomarkers to accurately predict nine different forms of liver disease. Using liquid chromatography tandem mass spectrometry (LC-MS/MS) with multiple reaction monitoring (MRM), serum and liver samples spiked with gamma-glutamyl peptide standards were analyzed to estimate accuracy. Unexpectedly, the recovery rates for several gamma-glutamyl peptides in the serum samples were quite low, whereas values for some gamma-glutamyl peptides in the liver samples were highly elevated. Most of these peptides were barely retained on the reverse-phase column, resulting in significant ion suppression or enhancement. In contrast, a capillary electrophoresis tandem mass spectrometry (CE-MS/MS) method with MRM was minimally affected by matrix effects. Of the 39 tested compounds, most of gamma-glutamyl peptides that did not contain a thiol substituent in its structure gave acceptable recoveries (70-120%), and limits of detection for the analytes were between 3.6 and 800 nmol/1 with pressure injection at 5 kPa for 10s (ca. 10 nl). The CE-MS/MS method provided high resolution and proved to be highly selective and sensitive, its utility being demonstrated by the determination of gamma-glutamyl di- and tripeptides in serum and liver samples. (C) 2014 Elsevier B.V. All rights reserved.