The objective of principal component projections of mass spectra is to find classes of compounds with common or similar properties. Sufficiently separated classes can then be used to investigate the class membership of an unknown spectrum. Spectra Projector allows you to add an external spectrum, which was not used for classification, to the projection plane. If the added spectrum is clearly projected into a particular class region, you can assume that this compound has similar, usually structural, properties.

The figure below shows that two groups are separated into clusters. We can add the unknown spectrum to the projection plane, by pasting or opening its spectrum into Spectra Projector. The projection of this external spectrum clearly shows that it belongs to the nicotine class (squares – PCA or triangles - Fuzzy Clustering). This result can then be finally confirmed or rejected using the fragmentation pattern of nicotine.