Spectrophotometric determination of microamounts of thorium with thorin in the presence of cetylpyridinium chloride as surfactant in perchloric acid

A simple and more sensitive spectrophotometric method is developed for determination of thorium using thorin as a chromogenic reagent in the presence of cetylpyridinium chloride (CPC) in perchloric acid. The reaction was instantaneous and complex was found stable for 168 h. A significant bathochromic shift was noted in the presence of CPC. The determination range was enhanced from 25 to 30 mu g mL(-1) with molar absorptivity of 2.95 x 104 L mol(-1) cm(-1) at 25 +/- A 5 A degrees C. Sandell's sensitivity was calculated to be 6.8 ng cm(-2) at 581 nm. Relative standard deviation was reduced from 4.25 to 2.5. The interference of Ni2+, Mn2+, Sn4+, phosphate, EDTA, sulphate and tartrate has been reduced significantly in the presence of surfactant. The validity of the proposed method was tested by determining thorium in Certified Reference Materials.