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k 0 -INAA / Trace elements / Iron reference materials / Matrix removal / Solvent extraction Summary. Various trace elements in different types of iron based geological reference materials [JSS 804-1 (hematite), JSS 820-2 (limonite), SU-1 and SU-1a (iron-nickel-coppercobalt ores)] were investigated using k 0 -instrumental neutron activation analysis (k 0 -INAA). To avoid the interference of iron as the matrix element, a liquid-liquid extraction procedure with diisopropyl ether (DIPE) in hydrochloric acid solution and determination of trace elements in the inorganic phase was undertaken prior to irradiation. The k 0 -INAA method, applied to determine the content of the investigated elements, enabled the distribution of 39 elements to be followed through their corresponding intermediate/medium and long half-lived radionuclides. The possibility of determining the content of numerous trace elements after Fe separation is an important advantage of the proposed method. k 0 -INAA used to determine elements in the powdered materials and in liquid form after iron extraction enabled us to follow the losses and potential contamination of some elements in the liquid-liquid extraction process. Additionally, elimination of the matrix element lowered the detection limit for some trace elements compared to their corresponding values obtained by k 0 -INAA.

The crystal lattice of the isomorphous tetraaquabis(saccharinate)metal(II) dihydrates was employed as a structurally flexible coordination framework capable of sustaining large internal distortions to study the competitive inclusion of Jahn-Teller (JT) distorted d 9 ions, [Cu(H 2 O) 4 (sac) 2 ] 2+ , and JT-inactive d 5 ions, [Mn(H 2 O) 4 (sac) 2 ] 2+ , in binary solid solutions under thermodynamically controlled conditions of statistical mixing (sac ) saccharinate anion, C 7 H 4 NO 3 S -). Probing of the metal content of the solid phase showed a two-regime inclusion profile: increasing the ratio of the distorted cation relative to the undistorted one in the solution phase of up to about 35% results in linear dependence and preferred inclusion of the former with maximum concentration of 100% in the crystal and complete exclusion of the undistorted ion above that point. A mixed crystal with highest copper ratio of 63% was obtained from solution with 25% copper, which under the P2 1 /c crystal symmetry corresponds to sustainable integrity of the undistorted lattice by substitution of up to 2 / 3 of its sites. This stability limit shows that four out of the six sites around each [Mn(H 2 O) 4 (sac) 2 ] 2+ ion can be substituted by distorted [Cu(H 2 O) 4 (sac) 2 ] 2+ guests under conditions of thermodynamically controlled, statistically averaged exchange. The undistorted host is very tolerant toward inclusion of strongly distorted guests. When acting as host, the distorted ion is more discriminatory toward the undistorted guest. Along with the expectation from the JT theory, structural refinement of seven crystals, including a mixed crystal with composition of [Cu 0.126 Mn 0.874 (H 2 O) 4 (C 7 H 4 NO 3 S) 2 ](H 2 O) 2 , showed that metal-ligand distances are significantly affected by the metal substitution. Inclusion of the JT-active ion results in distortion of the coordination polyhedron by increasing the bond length difference between the two metal-O(water) bonds and also causes shortening of the M-N bond. Due to the rigidness caused by π-conjugation, the overall effect on the endocyclic geometry of the organic ligand is small. The anisotropic distortions around the metal ion are faithfully reflected in the stretching force constants of the coordinated water molecules and thus in the IR spectrum of the mixed crystals.

A method for trace elements determination in chalcopyrite, CuFeS2, by k0-instrumental neutron activation analysis (k0-INAA) was proposed. To avoid the interference of iron and copper as matrix elements, methods for their separation were applied. The copper interferences were eliminated by applying an electrolytic separation method. To eliminate iron interferences, a liquid-liquid extraction procedure by diisopropyl ether (DIPE) in hydrochloric acid solution and determination of trace elements in the aqueous phase were undertaken. The k0-INAA method was applied to determine the content of the investigated elements, making it possible to follow the distribution of even fifty elements (with intermediate/medium and long half-lived radionuclides) in the studied mineral. The important advantage of the proposed method is the possibility to determine the content of several trace elements after Fe and Cu separation. Additionally, the elimination of the matrix elements lowered the limit of detection for some trace elements in the water phase compared to their corresponding values determined by k0-INAA in the powder sample.