LC-EPI chromatograms of a DHN-MA synthetic standard and a human urine sample. (A) Negative ion electrospray EPI scanning of m/z 320 of a standard reaction mixture of DHN-MA. (B) Negative ion electrospray EPI scanning of m/z 320 of a human urine sample. (C) The EPI spectrum of synthetic DHN-MA shows fragments with m/z 191, m/z 143, and m/z 173. (D) The EPI spectrum of endogenous DHN-MA in a human urine sample shows the same fragments as the synthetic DHN-MA sample, with m/z 191, m/z 143, and m/z 173.