title: A solid-phase extraction method using Transcarpathian clinoptilolite for preconcentration of trace amounts of terbium in water samples.
abstract: BACKGROUND
  In spite of the fact that terbium is one of the rarest elements in the Earth's crust, it is frequently used for the production of high technological materials. At the result, an effective combination of sample preparation procedure and detection method for terbium ions in different matrices is highly required. The solid-phase extraction procedure with natural Transcarpathian clinoptilolite thermally activated at 350 °C was used to preconcentrate trace amounts of terbium ions in aqueous solutions for a final spectrophotometric determination with arsenazo III.
  
  
  RESULTS
  Thermogravimetric investigations confirmed the existence of relations between changes that appeared during dehydratation of calcined zeolite and its sorption affinity. Since the maximum of sorption capacity towards terbium was observed at pH 8.25, a borate buffer medium (2.5 · 10(-4) М) was used to maintain ionic force and solution acidity. Terbium was quantitatively removed from the solid-phase extraction column with a 1.0 M solution of sodium chloride (pH 2.5). The linearity of the proposed method was evaluated in the range of 2.5-200 ng · mL(-1) with detection limit 0.75 ng · mL(-1).
  
  
  CONCLUSIONS
  Due to acceptable recoveries (93.3-102.0 %) and RSD values (6-7.1) from spiked tap water, the developed method can be successfully applied for the determination of trace amounts of terbium ions in the presence of major components of water. Graphical abstractSorption of terbium(III) ions on clinoptilolite.
authors: Faculty of Chemistry, Ivan Franko National University of Lviv, 6 Kyryla and Mefodiya St., 79005 Lviv, Ukraine ; Department of Chemistry and Physics, Lviv Academy of Commerce, 9 Samchuka St., 79011 Lviv, Ukraine.
authors: Volodymyr O
authors: VO
authors: Vasylechko
authors: Faculty of Chemistry, Ivan Franko National University of Lviv, 6 Kyryla and Mefodiya St., 79005 Lviv, Ukraine.
authors: Galyna V
authors: GV
authors: Gryshchouk
authors: Faculty of Chemistry, Ivan Franko National University of Lviv, 6 Kyryla and Mefodiya St., 79005 Lviv, Ukraine.
authors: Victor P
authors: VP
authors: Zakordonskiy
authors: Faculty of Chemistry, Ivan Franko National University of Lviv, 6 Kyryla and Mefodiya St., 79005 Lviv, Ukraine.
authors: Olga
authors: O
authors: Vyviurska
authors: Department of Environmental Safety and Nature Protection, Lviv Polytechnic National University, 12 Bandera St., 79013 Lviv, Ukraine.
authors: Andriy V
authors: AV
authors: Pashuk
keywords: Clinoptilolite; Preconcentration; Solid-phase extraction; Terbium