Abstract On the basis of affinity of Al3+ ions toward functional
groups of 3-hydroxy-2-naphthalenecarboxylic acid
(3H2NA), a high stable complex between Al3+ and 3H2NA
in 5 % methanol/water solution was established. The mole
ratio method showed that a stable complex by taking part of
acetate and 3H2NA with the stoichiometric ratio of 1:1:1
and stability constant of 8.6×106 is formed. Under the
optimum conditions for the complex formation, a rapid
spectrofluorometric determination of trace amounts of Al3+
(λex=366 nm, λem=460 nm) was proposed. The optimum
conditions involve 3H2NA concentration of 1.0×10−5 M,
buffering pH of 4.5 (acetic/acetate system), and ionic strength
of 0.01 M. The fluorescence intensity exhibited a good linearity
against the Al3+ concentration in the range 5.0×10−8
–5.0×
10−6 M with the detection limit of 1.3×10−8 M. No considerable
interference was observed due to the presence of
coexisting anions and cations. The method was applied successfully
to the determination of trace amounts of Al3+ in milk.
Validation of the measurements was confirmed using graphite
furnace atomic absorption spectrophotometry