Determination of thallium in soils by flame atomic absorption spectrometry

A method is described for the determination of T1 in soils by FAAS, involving extraction of T1 from 5 g of soil by digestion with HClO4/HNO3 followed by separation of the extracted T1 into 5 mL of diisopropylether from HBr solution, including Ce(SO4)2. T1 in the organic phase is determined by direct aspiration into the spectrophotometer. The percentage relative standard deviation (% RSD) for 5 replicate samples is about 1%. The detection limits (S/N = 3) of this method are 0.001 mg/L for aqueous solution and 0.02 mg/kg DW for soil, when 50 mL of soil solution corresponding to 2.5 g soil are used. The T1 concentration even of unpolluted soils can be determined. The method was shown to be unaffected by the presence of various ions in soil and was able to recover nearly 100% T1 added to soils. The arithmetic mean (range) of 18 Japanese unpolluted surface soils was 0.33 (0.10–0.56)mgT1/kgDW.