Figure 1

LC-ESI⁽⁺⁾-MS/SRM chromatograms of dexamethasone in a post-race plasma, dexamethasone as calibrator and betamethasone as an isomer of dexamethasone. Top three panels represent blank plasma (A), blank plasma + IS (B) and solvent blank (C), all of which were scanned for the presence of dexamethasone only at m/z 393 → 355. Panel D is dexamethasone detected in the post-race plasma sample collected from the alleged horse while panel E shows chromatographic resolution of dexamethasone (left) from betamethasone (right) spiked in blank plasma, extracted and analyzed. The t_R (1.05 min) of post-race plasma containing dexamethasone was similar to that for dexamethasone spiked plasma (calibrator) and the difference was within ± 0.1 min.