"Nanooptics and photonics"

Sorption-luminescence method for determination of cerium using clinoptilolite
Vasylechko V.O.1,2, Sak H. P.1, Gryshchouk G.V.1, Gloskovsky A.3, Kalychak Ya.M.1, Voloshinovskii A.S.1, Vistovskyy V.V.1
1 Department of Analytical Chemistry and Department of Experimental Physics, Ivan Franko National University of Lviv. Kyryla and Mefodiya Str., 6, Lviv-79005, Ukraine.
E-mail: vasylechko@ukr.net
2 Department of Natural Sciences and Environment Protection, Lviv University of Trade and Economics. Samchuka Srt., 9, Lviv-79011, Ukraine.
3 Deutshes Electronen-Synchrotron (DESY), Notkestrabe 85,22607 Hamburg, Germany

Cerium is the most abundant of the lanthanide elements. Lanthanides reveal almost identical chemical properties. However, lanthanides essentially differ in their optical properties, in particular, the ability for absorption and emission of excitation energy. This luminescence (LM) is specific for each lanthanide. This fact is the basis for selective luminescent methods of lanthanides determination. Sorption of elements being determined on the solid matrix is one of the efficient methods that can increase a sensitivity and selectivity of LM determination. 
Promising materials for solid phase spectrofluorometry are natural zeolites activated by REE ions. The possibility for LM determination of Ce using Transcarpathian clinoptilolite as a sorbent was studied. The Ce(III)–clinoptilolite samples were obtained via lanthanide ions sorption from aqueous solutions at pH 4.5 on the zeolite in a solid phase extraction mode. Obtained samples Ce(III)–clinoptilolite were dried at room temperature.
For the excitation of LM samples rays with the wavelength of 255 nm were used. The intensity of the LM at 346 nm was chosen as an analytical parameter for the quantitative determination of Ce. The oxidation of Ce3+ to Ce4+, which occurs during calcination of the Ce3+– clinoptilolite sample at 500 C, leads to complete disappearance of LM of this luminophore. Linear calibration range of Ce3+ concentration with the detection limit of 5 ng·mL-1 is within 14–190 ng·mL-1. The proposed method can be used for cerium determination in the presence of many rare earths.