Because of the non-specific ionization with atmospheric-pressure ionization methods, numerous ion-molecule reactions take place in the ion source, especially with complex samples which are not fully separated.These reactions lead to unclear spectra and often to considerable ion suppression.Currently, quantitative analysis of complex samples by mass spectrometry, with little or no ion suppression, is possible only with either high-performance pre-separation by means of hyphenated techniques such as GCxGC, LCxGC, and LCxLC, which ensure baseline separation of all matrix components, or with stable-isotope-labeled standards.In LCxLC the peak capacity 2Dn and the orthogonality O are often used as parameters of the resolving power.Unfortunately, these parameters are not easily accessible from the chromatogram.In this work we will present a novel method, based on a vector model, for the determination of the peak capacity from data easily accessible experimentally.