A new very sensitive and selective chromogenic reagents prepared by the reaction of Schiff base with maleic anhydride (MA) and 1,4-butane (I), ethylene (II), 1,6-hexamethylene (III) and 1,2-propane diol (IV), respectively, were synthesized and studied for the determination of trace lead in detail. In 0.1molL−1 NaOH medium, lead reacts with polyester to form a yellow complex, which gives a maximum absorption at 462, 478, 482 and 495 nm using I, II, III and IV respectively. Beer’s law is obeyed over the concentration ranges 0.04-1.20μgmL−1, whereas optimum concentration ranges as adopted from Ringbom method was 0.10-1.05μgmL−1. The molar absorptivity, Sandell sensitivity, detection and quantifi cation limits are also calculated Ca (3500-fold), Mg (2250-fold), Sr (1250-fold), Ba (1000-fold), Al (1500-fold), Bi (800-fold), Fe (2500-fold) Co (1100-fold), Ni (1000-fold), Cu (900-fold), Zn (1300-fold), Cd (2500-fold), and Ag (750- fold) do not interfere with the determination of lead. The chromogenic system is remarkably superior to other reagents, especially porphyrin compounds. The infl uence caused by oxygen in air or in solution can be easily eliminated by adding Na2SO3. The reaction is very stable, the stability constant of the complex being 1.44 x 1045. The chromogenic reaction is completed within 2.0 min at room temperature. The proposed method has been applied to the direct determination of trace lead in clinical samples. The accuracy and precisio n are both very satisfactory.
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