Rapid and sensitive hydrophilic interaction chromatography/tandem mass spectrometry method for the determination of glycyl-sarcosine in cell homogenates

A rapid, selective and sensitive hydrophilic interaction chromatography/tandem mass spectrometry (HILIC/MS/MS) was developed and validated for the determination of glycyl-sarcosine (Gly-Sar) in Caco-2 cell homogenates. After a simple protein precipitation with acetonitrile, the analyte was separated on a HILIC column and detected by a triple quadrupole mass spectrometry equipped with an electrospray ionization (ESI) source. The method was linear among the concentration range of 1–2000 ng/mL for Gly-Sar and the lower limit of quantification (LLOQ) was 1 ng/mL using as little as 50 μL of cell homogenates. The intra-day and inter-day relative standard deviations (RSD) were less than 15% and the relative errors (RE) were all within ±15%. The validated method was successfully employed in the study of Gly-Sar uptake inhibition in Caco-2 cells by valcytarabine, a potential substrate of the peptide transporter 1 (PEPT1).