Analytical Sciences


Abstract − Analytical Sciences, 19(9), 1269 (2003).

A New Selective Chromogenic Reagent for the Spectrophotometric Determination of Thallium(I) and (III) and Its Separation Using Flotation and the Solid-Phase Extraction on Polyurethane Foam
Khaled S. ABOU-EL-SHERBINI,* Gamal A. E. MOSTAFA,** and Mohamed M. HASSANIEN*** 
*Department of Inorganic Chemistry, National Research Centre, Dokki, Cairo, Egypt
**Microanalytical Laboratory, Department of Applied Organic Chemistry, National Research Centre, Dokki, Cairo, Egypt
***Department of Chemistry, Industrial Education College, Beni-Suef, Egypt
A new sensitive chromogenic reagent, 9,10-phenanthaquinone monoethylthiosemicarbazone (PET), has been synthesized and used in the spectrophotometric determination of Tl(III). In HNO3, H2SO4 or H3PO4 acids, PET can react immediately at room temperature with Tl(III) to form a red 2:1 complex with a maximum absorption at 516 nm. The different analytical parameters affecting the extraction and determination processes have been examined. The calibration curve was found to be linear over the range 0.2 - 10 ug cm-3 with a molar absorptivity of 2.2 x 104 dm3 mol-1 cm-1. Sandell's sensitivity was found to be 0.0093 ug cm-2. No interference from macroamounts of foreign ions was detected, except for Pd(II). However, Pd(II) does not affect the determination process, because its complex with PET has its lambdamax at 625 nm. The proposed method has been applied to the determination of Tl(I and III) in synthetic and natural samples after separation by flotation (in oleic acid/kerosene) and solid-phase extraction (on polyurethane foam) techniques. The two methods were found to be accurate and not subject to random error, but solid-phase extraction was preferred because it is cheap, simpler and there is no contamination risk coming from flotation reagents.