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A new spectrophotometric reagent for the determination of trace amounts of fluoride has been introduced. This method is based on the decolorization of a complex of Al(III) with xylenol orange (XO) as an ultra-sensitive colored reagent. Since the Al-XO complex plays an important role in this method, the protonation and complexation of XO with Al(III) at an ionic strength of 0.1 mol L -1 at 25 C has been studied by a spectrophotometric global analysis method. The EQUISPEC program was used to evaluate the protonation constants of XO and the stability constants of the formed complexes with Al(III). The protonation and the stability constants of the major complex species such as ML, MLH and MLH2, were determined. Finally, a spectrophotometric method for the assay of fluoride based on a decrease of the color intensity of the Al-XO complex, in an aqueous solution has been designed. The effects of some important variables on the determination of fluoride based on the proposed method were investigated. The method was applied to the determination of fluoride under the optimum conditions (pH 5.2, ionic strength 0.1 mol L -1 , 25 C). The determination of fluoride in the range of 0.08 -1.4 μg mL -1 (SD = 1.2%) was successfully performed. Interferences of Fe(III) were easily eliminated by using ascorbic acid. The proposed method was applied to the determination of trace amounts of fluoride content of some real water samples.

A new lead complex, [Pb(Q)2] (1) (Q=quinoline-2-carboxylic acid), was prepared via conventional electrochemical method in a fast and facile process and fully characterized by (1)H and (13)C NMR, IR, UV spectroscopies and elemental analysis. The nano-structures of same compound were successfully prepared at 25, 48 and 60°C by a facile and environment-friendly sonoelectrochemical route. The new nano-structure particles were characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analysis. Thermal stability of single-crystal and nano-size samples of the prepared compound was studied by thermogravimetric and differential thermal analysis. The effect of sonoelectrochemical temperature on particle size has been investigated, and possible explanations offered. The photoluminescence properties of the nano-structured and crystalline bulk of the prepared complex at room temperature in the solid state have been investigated in detail. The results indicate that the size of the complex particles has an important effect on the optical properties of it. The prepared complexes, as bulk and as nano-particles, were utilized as a precursor for preparation of PbO nanoparticles by direct thermal decomposition at 600°C in air. The nano-structures of PbO were characterized by scanning electron microscopy, X-ray powder diffraction and IR spectroscopy.

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