Fig. 1From: A new approach for urinary vanillylmandelic acid determination using eVol microextraction by packed sorbent coupled to liquid chromatography-tandem mass spectrometryLC-MS/MS chromatograms of a 1 μg/mL calibration standard, b healthy patient urine, and c abnormal patient urine: vanillylmandelic acid (VMA), vanillylmandelic acid-d3 (VMA-d3)Back to article page