A major matrix effect that hampers nuclear analysis with charged particles is found in the range differences which charged particles experience in samples and comparators. The determination of lithium in ores was attempted by the previous determination of the ranges of protons therein. This was achieved by the homogeneous spiking of the ores with pure boron compounds of known composition and therefore known calculated ranges. Pure lithium compounds, also with known calculated ranges, were used as lithium standards. Determinations were carried out by proton-induced prompt photon spectrometry on nuclides of lithium and boron. Results obtained for standard reference ores, SRM 181 and-183, were in good agreement with the specificfied values.