3.6. Study of interferences
The effects of 30 foreign ions on the determination of
0.1gml−1 tin by the proposed method were examined. The
tolerance limits for these ions are given in Table 2. A foreign
ion was considered to interfere seriously when it caused an error
of 5% in fluorescence signal. As can be seen, most of the ions
do not interfere when they are present in 100-fold excess. Only
Cu(II), Co(II), Fe(II), Fe(III) and V(V) interfered when present
at the same level as tin. But the concentrations of these ions in
canned products are very lowand therefore they do not cause any
interference in real sample analysis. However, the interferences
of the most of these ions might be eliminated, if necessary, by
using hydroxyethyle ethylenediamine triacetic acid (HEDTA)
as masking agent [8] and ion exchange resin (for vanadate ion).