Analytical methods and quality assurance

Abstract

In our study the method for the determination of Tl by ICP-MS was optimized. Both isotopes, 203 Tl and 205 Tl, were used for the measurement. Lutetium at a concentration 0.4 mg L -1 was used as an internal standard. Soil extracts were measured after dilution (1+4 with the solution of lutetium 0.5 mg L -1 ). Several soils from the International Soil Exchange Programme (WEPAL) were analyzed for the comparison of the results. For all tested samples the achieved results were in a good agreement with the results reported by WEPAL. A detection limit 1.2 µg kg -1 was achieved for the samples. The method was used for the determination of thallium in soils collected in the national monitoring programme (200 sites) and in the monitoring programme of the contaminated areas (27 sites). Topsoil and subsoil were sampled on each site and analyzed separately (454 samples were analyzed). The median value for the tested soils was 0.25 mg/kg, lower and upper quartiles 0.19 and 0.32 mg kg -1 respectively, 10 th and 90 th percentiles 0.16 and 0.41 mg kg -1 respectively and the maximum value was 2.83 mg kg -1 .

Comparison of aqua regia and HNO3-H2O2 procedures for extraction of Tl and some other elements from soils

“…Both procedures are comparable in results (differences lower than 10% for the most of the elements) for all the tested elements. Detailed discussion of the extraction methods and comparison of their extraction abilities in relation to the total contents was also given in previous papers [10,11,12,17] and is also a part of the discussion in the draft version of the ISO standard.…”

“…Tl was the element of most interest and therefore the sampling sites were chosen to achieve as wide range of Tl contents as possible. The data concerning the selection of the sampling sites were discussed in detail in our previous papers [10,11]. Soil samples were extracted according to ISO 11466 and slightly modified ISO/CD 20279 (2 g soil sample, 10 mL HNO 3 and 20 mL H 2 O 2 were used for the HNO 3 -H 2 O 2 extraction).…”

“…There is little detailed information on the Tl status of soils [8,9,10,11,12,13,14]. A median of 0.29 mg kg -1 and a maximum of more than 50 mg kg -1 were found for French soils [8,9], and a median value of 0.25 mg kg -1 and a maximum value of 2.83 mg kg -1 were found for more than 450 tested soil samples in the Czech Republic.…”

“…Tl and its compounds are non-essential, and they are toxic to all organisms. Demand for determination of Tl, especially in countries where soils derived from melanocratic granites occur, is expected to rise because Tl in soils is mostly of pedogeochemical origin [7,8,9,10,11,12].…”

“…Flame atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry (ICP/OES) are not very sensitive for the determination, without preconcentration. Electrothermal atomic absorption spectrometry is much more sensitive, but a Zeeman background correction and a stabilized temperature platform furnace have to be used [8,9,10,11]. Inductively coupled plasma mass spectrometry (ICP/MS) was found to be very suitable method for the determination of Tl [9,10,11].…”