Separation of isomers L-alanine and sarcosine in urine by electrospray ionization and tandem differential mobility analysis-mass spectrometry.

Sarcosine, an isomer of L-alanine, has been proposed as a prostate cancer progression biomarker [1]. Both compounds are detected in urine, where the measured sarcosine/alanine ratio has been found to be higher in prostate biopsy-positive group versus controls. We present here preliminary evidence showing that urine samples spiked with sarcosine/alanine can be partially resolved in 3 min via tandem differential mobility analysis-mass spectrometry (DMA-MS). Based on the calibration curves obtained for two mobility peaks, we finally estimate their concentration ratio in urine.