Avinash A. Patila, Zhe-Xuan Liua, Yi-Pang Chiua, Th? Khánh Ly L?ia, Szu-Wei Choub, Chun-Yen Chengb, Wen-Min Suc, Hong-Ting Liaoc, Justin Benedict A. Agcaoilia, Wen-Ping Penga
a. Department of Physics, National Dong Hwa University, Shoufeng, Hualien, 97401, Taiwan
b. AcroMass Technologies Inc., Hukou, Hsinchu, 30352, Taiwan
c. Department of Life Science, National Dong Hwa University, Hualien, 97401, Taiwan
Detecting megadalton matrix-assisted laser desorption/ionization (MALDI) ions in an ion trap mass spectrometer is a technical challenge. In this study, megadalton protein and polymer ions were successfully measured by MALDI linear ion trap mass spectrometer (LIT-MS) for the first time. The LIT-MS is comprised of a Thermo linear ion trap mass analyzer and a highly sensitive charge-sensing particle detector (CSPD). A newly designed radio frequency (rf) scan mode with dipolar resonance ejection techniques is proposed to extend the mass range of LIT-MS up to one million Thomson (Th). We analyze high mass ions with mass-to charge (m/z) ratios ranging from 100 kTh to 1 MTh, including thyroglobulin, alpha-2-macroglobulin, immunoglobulins (e.g., IgG and IgM), and polymer (∼ 940 kTh) ions. Besides, it is also very challenging for ion trap mass spectrometry to detect megadalton ions at low concentrations. By adopting high affinity carboxylated/oxidized detonation nanodiamonds (oxDNDs) to enrich IgM molecules and form antibody-nanodiamond conjugates, we have successfully reached ∼ 5 nM (5 μg/mL) concentration which is better than that by the other techniques.