[en] A new crown hydroxamic acid (NHDTAHA) is used for the extraction and spectrophotometric determination of vanadium (V). The molar absorptivity is 2.5 x 10⁴ L mol^-1 cm^-1 at 395 nm and the system obeys Beer's law over the range 0.05-3.0 ppm of vanadium. For ICP-AES (inductively coupled plasma atomic emission spectrophotometry) measurements, the extract can be directly aspirated, which enhances the sensitivity 25-fold and the limits for estimation are 2-120 ppb of vanadium. Vanadium has been determined in ores, steel, environmental and biological samples. (authors). 15 refs., 3 figs., 6 tabs

[en] Polystyrene-divinylbenzene-based Amberlite XAD-2 was functionalized with ortho-vanillinthiosemicarbazone and its analytical properties were investigated. The resin was used successfully for the separation and preconcentration of thorium(IV) and uranium(VI) ions prior to their determination by spectrophotometry and by ICAP-AES and GF-AAS, respectively. The influence of several ions as interferents is discussed. The resin exhibits good chemical stability, reuseability, and a faster rate of equilibration for their determination. The proposed method has been applied to sequential chromatographic separation of thorium(IV) and uranium(VI) on river water samples with good analytical reliability such as recovery of 97--98%, relative standard deviation of 2--3%, and a detection limit of 100 ng/mL. The present method is also used for their determination in monazite sand and some standard geological materials

[en] A method for the preconcentration and trace determination of thorium with crown hydroxamic acid (NHDTAHA) is described. The thorium is extracted from the chloroform solution of NHDTAHA at pH 4 which gives a colourless extract, λ_max = 365 nm; ε = 9.4 x 10^-3 1 x mol^-1 x cm^-1. The extract is directly inserted in the plasma for ICP-AES measurements of thorium. A linear calibration graph was obtained between 15-150 ng x ml^-1 of thorium. The proposed method has been applied for the determination of thorium in the presence of several diverse ions in monazite sand, rare earth sand and in sea water. (author)