Determination of Microgram Quantities of Thallium in Aluminum-, Iron-, and Nickel-Base Alloys

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Abstract
Chemical techniques are required for the determination of trace constituents in commercial nickel and its alloys. An adequate method does not exist for the determination of microgram quantities of thallium; therefore, an extraction-atomic absorption method has been developed. Trace quantities of thallium in nickel are quantitatively extracted from a 10% hydrochloric acid solution containing 2% ascorbic acid and 9% potassium iodide by a 5% solution of tri- n-octylphosphine oxide in 4-methylpentane-2-one (MIBK). The MIBK extract containing the thallium is then nebulized directly into the atomic absorption flame. The concentration range for the determination of thallium in MIBK is an order of magnitude lower than for aqueous media. The proposed analytical technique is accurate and rapid and has a precision (σ) of ±0.15 ppm at the 2.00 ppm level. The limit of detection is 0.1 ppm of thallium. The method is also applicable to aluminum- and iron-base alloys. The solvent extraction procedure used to isolate thallium has also been validated for antimony, bismuth, lead, and tin and can also be applied to the determination of cadmium, copper, indium, and zinc.