Lecture 23

Mass Spectroscopy III

Harris Ch.22

Nitrogen Rule

Mass Number

C 12H 1O 16F 19Cl 35 or 37Br 79 or 81I 127S 32Si 28

N 14

CH4 16

CnH2n+2 Even number

Replace H by any group:

OH, F, Cl, Br, I, SH, SiH3

Still even number!

Replace 2H by O, S, etc.Still even number!

Any saturated hydrocarbon

Replace by –NH2 ODD!

Mass number is odd: I have odd number of N atoms

High resolution MS

LSD

A 1.0 g whole blood or 1.0 mL urine was mixed with 20 μL 0.05 mg/l aqueous LSD-D3. The sample was extracted with 1.0 mL butyl acetate after adjusting pH with 1.0 mL 1 M sodium carbonate. After centrifugation for 10 min at 3600 rpm, the organic fraction was removed and evaporated to dryness at 40 °C under a steam of pure nitrogen. It was reconstituted in 100 μL mobile phase and transferred to a brown autosampler vial and 20 μL was injected into the chromatographic system.

LSD 324 → 223 324 → 208 0.61Iso-LSD 324 → 281a 324 → 208 1.0M-LSD 356 → 237 356 → 222 0.84IS (D3-LSD) 327 → 226 – –