Isotope Ratio Mass Spectrometry (IRMS) 
11 
Isotope Ratio Mass Spectrometry (IRMS) 
The IRMS can be considered as a special type of mass spectrometry where 
the content of stable Isotopes Is measured. In the case of carbon, It Is 12 C and 
13 C, however, analysing 1 H and 2 H might also be an option. 
13 C content Is expressed In per mil as the ratio 13 C : 12 C, normalised to the ratio 
of a standard and formed as the difference (8 to this double ratio of the stand 
ard Itself): 
The PDB (Pee Dee Belemnlte)-Standard Is a marine fossil limestone with an 
extraordinary high content of 13 C. As most of the other materials on earth have 
lower 13 C contents, their values according to this equation turn out to be nega 
tive. In geological sciences, these calculations are used to classify and cate 
gorise materials according to their origin as shown In Fig. 6. 
As paraffin wax Is a product of mineral oil, or “petroleum”, a 8 13 C value In the 
same range (-35 to -20) Is expected (Fig. 6). 
Consequently, comparing Isotopic signatures of paraffin wax samples might 
provide meaningful Information regarding a common source of two samples.