Fragment ions are usually structurally significant.
FAB requires the use of a matrix compound. Interactions between the matrix and the sample may complicate the spectral analysis. High resolution analysis using FAB is possible provided a reference standard which is compatible with the test sample and matrix is available. FAB is not compatible with Gas Chromatograph and can be used with a Direct Insertion Probe only. Before submitting a sample for analysis, check the literature for a suggested matrix compound.