The detected product ions for the CML-4-MBQ adduct were at m/z 206.1187, 152.0717, 130.0874, and 84.0815, and the structural formula was subsequently deduced to prove that the main binding site for 4-MBQ and CML was at the secondary amine of CML. Here, BCR is linked to chronic myelogenous leukemia, BCR-ABL1 positive.