Development of a Novel Mass Spectrometric ... - Jacobs University

Introduction
Kendrick mass of 14.0000 Da. The ratio of nominal mass and accurate mass of
CH 2 is multiplied by the mass measured by MS to convert it into Kendrick mass.
Kendrick mass = IUPAC mass x (14/14.01565)
Compounds with the same (N, S and O) composition and the same number of
rings plus double bonds but different numbers of CH 2 units in alkyl side chains for
example will differ in Kendrick mass by integer multiples of 14.0000 Da. These
compounds are thus easily identified as members of a homologous series. Stated
another way, members of a homologous series will have the same Kendrick mass
defect (KMD), defined as:
KMD = [Kendrick nominal mass – Kendrick exact mass] x 1,000
This is unique to that series and will be plotted as a homologous series of
compounds on one horizontal line. The KMD value remains unique as long as the
class and type of compounds remain identical. The Kendrick formation has been
successfully applied to crude oil samples using the CH 2 mass increment. An
example of Kendrick is given in Figure 1-6 where part of elemental composition of
a crude oil has been sorted. Not only does 2-D Kendrick mass plots aid in the
assignment of unique elemental compositions but they also constitute a chemically
sorted display of thousands of mass spectral data points whose mass is higher than
~400 Da. In other words once a few related compounds are identified, extension of
that pattern to higher mass allows for confident elemental composition assignment
of ions whose mass is too high to allow a unique assignment based on the
measured mass. 105
25