The reliability of the relative sensitivity factor (RSF) approach for secondary ion mass spectrometry (SIMS) quantification of the leached layers on glass was investigated by measuring comparable samples of glass with SIMS and RBS (Rutherford backscattering spectrometry). The RSF factors were calculated using the nominal bulk compositions. Accurate results can be obtained only when the leached layer and the bulk glass have the same major elemental compositions (Si and O) and the matrix effect is inhibited. The concentrations of the different elements in the leached layer obtained from the comparable samples measured by SIMS and RBS are coincident within a factor of 2