Highly sensitive spectrofluorimetric determination of trace amounts of lead with a new fluorescent reagent, 2-hydroxy-1-naphthaldehydene-8-aminoquinoline

A new fluorescent reagent, 2-hydroxy-1-naphthaldehydene-8-aminoquinoline (H NAAQ), was synthesized. The fluorescent reaction of this reagent with lead was also studied. Based on this chelation, a highly sensitive spectrofluori metric method was developed for the determination of trace amounts of lead in a water-ethanol (5 + 1, v/v) medium at pH = 9.4. Under these conditions, the Pb-HNAAQ complex has excitation and emission maxima at 398 and 450 nm, respectively. The linear range of the method is from 0 to 100 mug l(-1) an d detection limit is 0.28 mug l(-1) of lead. Interference of other ions was studied. In strongly basic media most interfering metal ions form precipit ates of hydroxides or oxides and can be removed efficiently through filtrat ion while the residual cations can be removed with a cation-exchange resin. Hence, the selectivity of the method can be increased considerably. The pr ocedure can easily be performed and affords good precision and accuracy. Th e method was successfully applied to the determination of lead in wheat and rice flour.