USE OF COUNTERCURRENT PARTITION CHROMATOGRAPHY FOR THE PRECONCENTRATION AND SEPARATION OF INORGANIC-COMPOUNDS - GROUP EXTRACTION OF ZR, HF,NB, AND TA FOR THEIR SUBSEQUENT DETERMINATION BY INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY

The possibility of the group preconcentration of Zr(IV), Hf(TV), Nb(V) , and Ta(V) by countercurrent partition chromatography using extractio n systems based on di-2-ethylhexylphosphoric acid (D2EHPA), N-benzoyl- N-phenylhydroxylamine (BPHA), and tetraoctylethylenediamine (TOEDA) wa s studied. It was demonstrated that systems with D2EHPA can extract an d preconcentrate Zr(IV), Hf(IV), and Nb(V) into the organic stationary phase and can separate them from the majority of other elements. The preconcentration of Zr(IV) and Hf(IV) and subsequent back extraction, as well as the selective extraction of Zr(IV), Hf(IV), Nb(V), and Ta(V ) into a small (4 mt) volume of the organic phase can be performed wit h a mixture of D2EHPA and BPHA. The conditions for the preconcentratio n of Zr(IV), Hf(IV), Nb(V), and Ta(V) in the TOEDA-based system were s elected. A method was proposed for the group extraction of Zr(IV), Hf( IV), Nb(V), and Ta(V) from solutions of geological samples. At the sta ge of the preconcentration of Zr(IV), Hf(IV), Nb(V), and Ta(V) with a 0.1 M solution of TOEDA in chloroform from a mixture of oxalic (0.01 M ) and hydrochloric (0.1 M) acids, matrix components were eluted with a flow of the mobile phase. Then, upon changing the eluent (2.0 M HCl), the four elements were extracted to a small (7-8 mt) eluate fraction. The results of determining Zr, Hf, Nb, and Ta by inductively coupled plasma atomic emission spectrometry in the international standard refe rence material Granite GM after their preconcentration in the system w ith TOEDA are in agreement with the certified values.