preconditions are needed to be considered. Firstly, the response factors of the
compounds have to be very similar or even identical. This accounts for chemically
similar compounds and, in case of mass spectrometric analyses, similar mass spectra.
Secondly, the compounds have to appear in the analyses, that implies to occur in the
PCB 101
2,2’,4,5,5’-pentachlorobiphenyl
2,2’,4,5,5’-pentachlorobiphenyl
(PCB 101)
analyte with unknown
concentration
13 C labelled 2,2’,4,5,5’pentachlorobiphenyl
(+ m/z 12)
internal standard with known
concentration
time (min)
m/z 338
m/z 326
Cl
Cl
Cl
Cl
Cl
Fig. 5.22 Example of an internal calibration procedure for PCB analyses by GC/MS
5.2 Quantitation
125