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. Author manuscript; available in PMC: 2013 Nov 1.
Published in final edited form as: Anal Biochem. 2012 Jul 31;430(1):4–15. doi: 10.1016/j.ab.2012.07.022

Table 2.

Electron-capture negative-ion chemical ionization (ECNICI) mass spectra of the pentafluorobenzyl derivatives of unlabeled AECK-DD and 13C2-AECK-DD

AECK-DD
m/z (intensity, %)		 13C2-AECK-DD
m/z (intensity, %)		 Ion assignment
408 (6) 410 (2) M−•
388 (9) 390 (3) [M–HF]−•
368 (71) 370 (49) [M–2×HF]−•
328 (100) 330 (100) [M–4×HF]−•
308 (37) 310 (27) [M–5×HF]−•
226 (56) 228 (61) [M–PFB]−
181 (4) 181 (10) [PFB]−