Reference Materials

McLafferty & Turacek, “Interpretation of Mass Spectra”, 4th Ed. (University Science Books)

NIST: http://webbook.nist.gov/chemistry (online spectra)

University of Sheffield: http://www.shef.ac.uk/~chem/chemputer (Isotope envelope calculator)

A generic mass spectrometer

Magnetic Mass Filtration

m/z = 4.82 x 10-5 B2r2/V

m Ion massz Ion chargeB Magnetic field strength (Gauss)r Radius of ion path (cm)V Ion accelerating voltage (volts)

A typical spectrum

Isotopic Abundances for Important Elements

H: 1H 100 2H 0.015 3H <0.001

C: 12C 100 13C 1.1 14C <0.1

N: 14N 100 15N 0.37

O: 16O 100 17O 0.04 18O 0.20

Cl 35Cl 100 37Cl 32.5

Br: 79Br 100 81Br 98

Si: 28Si 100 29Si 5.1 30Si 3.4

S: 32S 100 33S 0.8 34S 4.4

Classification of elements

A A+1 A+2

H C OF (19F) N SiP (31P) SI (127I) Cl

Br

Contribution to (M+1) vs. Number of Carbons

Halogen Patterns

Example 1

12,42 13,17 14,17 15,1 26,16827,999 28,17 29,1

Example 2 12,5 13,9 14,21 15,466 16,646,14 47,25 48,11 79,63 80,1681,63 82,16 91,68 92,40 93,20994,999 95,149 96,942 97,11

Calculating unsaturations

(R + D) = x – ½ y + ½ z + 1for CxHyNzOn

Cl, Br, F =HS = OP = NSi = C

Diethyl Ether

Triethylamine

Decane

2,7-Dimethyloctane

Hexylbenzene

Generation of the m/z = 91 peak

Ephedrine

Methamphetamine

Phentermine

THC (Tetrahydrocannabinol)

MDMA (Ecstasy)