Interest in preconcentration techniques for the determination of metals at ultratrace levels still continues increasingly because of some disadvantages of flameless atomic absorption spectrometry and the high costs of other sensitive methods in compared to flame atomic absorption spectrometry (FAAS). Among preconcentration techniques, solid-phase extraction is the most popular because of a number of advantages. In this work, thiol-containing sulfonamide resin was synthesized, characterized, and applied as a new sorption material for solid phase extraction and determination of lead in natural water samples. The optimization of experimental conditions was performed using the parameters including pH, contact time, and volumes of initial and elution solutions. After preconcentration procedure, FAAS was used for determinations. The synthesized resin exhibits the superiority in compared to the other adsorption reagents because of the fact that there is no necessity of any complexing reagent as well as high sorption capacity. Consequently, 280-fold improvement in the sensitivity of analytical scheme was achieved by combining the slotted tube atom trap-atomic absorption spectrometry (STAT-FAAS) and the developed preconcentration method. The limit of detection was found to be 0.15 ng mL À1 . The Pb 2þ concentrations in the studied water samples were found to be in the range of 0.9-6.7 ng mL À1 .

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The aim of this study is to investigate the concentrations of U, Th, V, Mo, and Zr in natural waters taken from Turkey. Among these water species, Lake Van is the largest soda lake and the fourth largest closed basin on Earth Mediterranean Sea water. Mean Mo and V concentrations in the studied water samples were found to be in ranges of 0.1-17 and 2.7-113 mg L À1 , respectively. The obtained highest U concentration in Lake Van correlates with the highest Mo and Zr levels compared to the Lake Hazar and river waters. These results imply that there is a young occurrence of uranium minerals around Lake Van. It is concluded that there is about 50.000 ton of uranium in Lake Van water.