Table 1. Exact Masses of Common Organic Isotopes and their mass defect.

Isotope	Exact Mass (Da)	Mass Defect (Da)	Isotopic Composition
1H	1.007825	0.007825	0.999885
2H	2.014102	0.014102	0.000115
12C	12.000000	0.000000	0.9893
13C	13.003355	0.003355	0.0107
14N	14.003074	0.003074	0.99636
15N	15.000109	0.000109	0.00364
16O	15.994915	-0.005085	0.99757
18O	17.999161	-0.000839	0.00205
31P	30.973762	-0.026238	1.0000
32S	31.972071	-0.027929	0.92223