Fig. 6From: A new approach for urinary vanillylmandelic acid determination using eVol microextraction by packed sorbent coupled to liquid chromatography-tandem mass spectrometryMethod comparison of LC-MS/MS and HEI method for the analysis of VMA. a Scatter plots of VMA results by LC-MS/MS (y axes) vs by the HEI method (x axes). b Bland-Altman plots of ratio (y axes) vs average values (x axes) for VMA results by the LC-MS/MS and HEI methodBack to article page