Spectrophotometric microdetermination of gadolinium(III) and terbium(III) with xylenol orange in presence of cationic cetylpyridinium bromide as a surfactant

摘要

Xylenol orange (XO) has been reported earlier to form violet colored binary complexes with several lanthanides and used for the determination of several metal ions. The addition of cationic surfactant, cetylpyridinium bromide (CPB) to the colored solution of xylenol orange resulted into discoloration at specific pH values which is due to the interaction of anionic XO with cationic CPB. The addition of specific metal ions to this decolorized solution resulted into formation of deeply colored water soluble stable ternary complexes with a large bathochromic shift of 42 nin with increase in absorbance at shifted wavelength. Stoichiometric composition of 1 : 2 : 4 (e.g. Gd~(III)-XO-CPB) has been observed by Job's method of continuous variation. The values of log K for both binary and ternary complexes have been calculated. The ternary complexes were formed in wider pH range with increase in stability and exhibited absorption maxima at 612 nm for both the metal ions understudy. Various analytical parameters like order of addition of reactants, effect of time and temperature, effect of reagent concentration, Beer's law, photometric ranges, Sandell's sensitivity and molar absorptivity have also been calculated and compared. The effects of interfering ions on determination of both the metal ions were studied. A simple, rapid and highly sensitive method for the determination of Gd~(III) and Tb~(III) with xylenol orange is proposed.