Analytical Chemistry

Figure 9.54

Mass spectra of tetrahydrocortisone. (a) EI;

(b) CI; (c) FI.

Table 9.10 Principle stable isotopes and relative abundances of some common elements

Element

Percentage abundance*

Isotope Isotope Isotope

carbon (^12) C (^10013) C 1.08
hydrogen (^1) H (^1002) H 0.016
nitrogen (^14) N (^10015) N 0.38
oxygen (^16) O (^10017) O 0.04 (^18) O 0.20
fluorine (^19) F (^100)
silicon (^28) Si (^10029) Si 5.10 (^30) Si 3.35
phosphorus (^31) P (^100)
sulphur (^32) S (^10033) S 0.78 (^34) S 4.40
chlorine (^35) Cl (^10037) Cl 32.5
bromine (^79) Br (^10081) Br 98.0