A liquid-liquid extraction has widely been used as one of the techniques by which trace metal ions in aqueous solution could be separated and concentrated. 1 However, some metal complexes that slightly dissolve in liquid solvent and are stable in solution at high temperature could be concentrated and extracted more effectively, rapidly and quantitatively by solid-liquid separation using microcrystalline naphthalene or benzophenone. 2,3 But this method suffers from the volatility of the fused organic material caused by a high temperature of 70 -90˚C. In order to overcome this difficulty, a modified technique based on the adsorption of metal complex at room temperature onto microcrystalline organic substance was used. 4,5 UV-Vis spectrophotometry has usually been used to determine the analytes after solid-liquid separation. [4][5][6][7][8] In the case of using UV-Vis spectrophotometry, however, the spectral interference due to overlapping of the maximum absorption wavelengths may occur when various metal ions are contained in a real sample. So, the atomic absorption spectrometry that had only slight spectral interference was used in this study.The determination of Fe 3+ , Co 2+ or Cu 2+ has been performed after solid-liquid separation. [8][9][10][11][12] Solid-liquid separation has been usually applicable to binary complexes, but in case of ternary complexes, only some metal ions could be separated. Such a ternary complex was not well formed and was unstable at high temperature.
13One example where such separation was applicable to a ternary complex was Fe 2+ -dipyridyltetraphenylborate. 14 Also, the metal-nitroso-R salt anionic complexes which metal ions were Fe 3+ , Co 2+ and Cu 2+ , were retained on tetradecyldimethylbenzylammonium iodide supported on naphthalene in column. 15 In this study, the determinations of Fe 3+ , Co 2+ and Cu 2+ were performed after separation and adsorption of their ternary complexes with nitroso-R salt and CTAB onto benzophenone at 30˚C. The ternary complexes of Fe 3+ , Co 2+ and Cu 2+ could simultaneously be preconcentrated with excellent efficiency at about room temperature by this technique. And this method was more sensitive, more rapid and had less spectral interference than with UV-Vis spectrophotometry.
Experimental
InstrumentationA GBC Model 903 flame atomic absorption spectrophotometer was used to determine Fe 3+ , Co 2+ and Cu 2+ . The measuring conditions were as follows: 10 cm 1-slot burner; air(16 l/min)-acetylene(1.5 l/min) flame; 0.5 nm spectral bandwidth; 12 mm burner height. The wavelengths and the lamp currents of Fe 3+ , Co 2+ and Cu 2+ were 248.3 nm, 240.7 nm and 324.8 nm, and 7.0 mA, 6.0 mA and 4.0 mA, respectively.To adjust pHs, a Bantax Model 300A digital pH meter with a combined glass and calomel electrode was used.
Reagents and solutionsChemicals such as iron(III) nitrate nonahydrate (Aldrich Co.), cobalt(II) nitrate heptahydrate (Aldrich Co.), copper(II) nitrate hexahydrate (Aldrich Co.), nitroso-R salt (BDH Chemical Co.), benzophenone (Yakuri Co.) and cetylt...
