Development of surfactant assisted kinetic method for trace determination of thallium in environmental samples

A simple and highly selective surfactant assisted kinetic spectrophotometric method for the determination of thallium has been developed. The method is based on the quantitative oxidation of Tl(I) to Tl(III) using bromine water where the resulting Tl(III) liberated iodine from potassium iodide in acidic medium. The liberated iodine was subsequently reacted with I− ion to form tri-iodide ions (I3−). The tri-iodide ions formed were further reacted with cetylpyridinium cation (CP+) which produced a violet ion associate species having a λmax of 512 nm at which reaction was monitored. The reaction variables such as time, temperature, reagent concentration and acidity were optimized for the indicator reaction to achieve maximum sensitivity. The linear regression calibration concentration range of 0.007-0.1 μg mL− 1 Tl(I) was established as the Beer's law was obeyed in this range. Sandell's sensitivity and molar absorptivity of the ion associate species in terms of thallium were determined to be 0.000133 μg cm− 2 and 1.99 × 106 L mol− 1 cm− 1 respectively. The limit of detection was determined as 0.0029 μg mL− 1. The developed method has successfully been applied for the determination of thallium in different environmental samples with satisfactory results.