Determination of trace amounts of selenium in poultry feedstuffs by gas chromatography.

In view of the importance of establishing reliable selenium concentration levels in different kinds of feedstuffs, the purpose of this work was to develop optimum experimental conditions for the isolation and GC determination of selenium as its chelate with 4-nitro-1,2-diaminobenzene. It was shown that ignition of the sample in an oxygen flask followed by reduction of Se(VI) to Se(IV) and the formation of 5-nitro-2,1,3-benzoselenadiazole chelate in HCl medium is a relatively rapid procedure giving a low blank value and allowing the determination of selenium in commercial feedstuffs and similar biological samples. The method was validated by the analysis of suitable certified or standard reference materials.

Determination of traces of indium, manganese, arsenic and antimony in zinc by neutron-activation analysis.

Destructive activation determination of the trace elements indium, manganese, arsenic and antimony in different samples of pure zinc metal by solvent extraction techniques is described. Determination of indium and manganese is based on the quantitative co-precipitation of both elements with lanthanum hydroxide, followed by their extraction with sodium diethyldithiocarbamate in the presence of potassium cyanide and their subsequent separation by selective stripping. The quantitative determination of arsenic and antimony is based on the extraction of their iodides from sulphuric acid solution with toluene.

Trace elements in some human milk samples by radiochemical neutron activation analysis.

Some trace element contents of samples of human milk, mainly colostrum and transitional milk, collected in the Ljubljana area of Yugoslavia, are reported. Analyses of As, Cd, Co, Cu, Hg, I, Mn, Sb, Se, Sn, V and Zn were performed by radiochemical neutron activation analysis, and the results are discussed briefly in the light of literature values.

Comprehensive RNAA of cadmium, cobalt, nickel, and copper using 109Cd, 57Co, and reactor-produced 67Cu as radioisotopic yield monitors.

An existing radiochemical NAA procedure for Cd, Co, and Cu was improved to allow determination of individual radiochemical yields by the radioisotopic tracer technique, thus eliminating errors owing to variable recovery. 109Cd was used as tracer for Cd determination via 115Cd/115mIn, 57Co for Co via 60Co, and potentially for Ni via 58Co, whereas as a novelty 67Cu, produced by reactor irradiation of ZnO of natural isotopic composition (by the 67Zn [n,p] 67Cu reaction) was used for Cu via the indicator nuclide 64Cu. The simple production and purification of 67Cu by anion exchange is described. Results for biological RMs are given and discussed.

Simple determination of iodine in small specimens of thyroid tissue.

This work describes a simple photometric determination of the iodine concentration in thyroid tissue, a method based on the well-known catalytic Sandell-Kolthoff reaction. The modified ceric arsenite reaction is very sensitive and does not require complicated laboratory equipment. It can be performed in any routine clinical laboratory if instructions are followed strictly. By means of this method iodine concentration can be determined even in small specimens, for instance puncture samples of thyroid tissue or thyroid glands of small animals (mouse). Previous to the analysis, the tissue is digested in a mixture of sodium chlorate and perchloric acid at 100 degrees C. Using this manner of digestion between 94 and 110% of iodine in the sample were recovered. Comparison with neutron activation analysis showed excellent agreement of the obtained values.

Iodine concentration in different human brain parts.

Iodine is one of the most important essential elements as demonstrated by the fact that its deficiency can cause goitre. Nevertheless, quantitative data on its concentration in biological materials, especially in the human brain, are scarce. There is therefore a demand for accurate and reliable information on iodine in these types of samples. The purpose of the present work was to determine the concentration of total iodine in some control human brain parts by rapid radiochemical neutron activation analysis. Our second goal was to determine I distribution between lipid fraction and in brain tissue without lipid by applying two types of solvent extraction methods. The results were checked by the analysis of biological standard reference materials with certified or literature values for iodine and good agreement was found.

Applicability of neutron activation analysis (NAA) in quantitative determination of some essential and toxic trace elements in food articles.

Accurate and reliable data on microgram and nanogram quantities of some essential and toxic elements in most food articles are very scarce. Neutron activation analysis (NAA), with its essentially blankfree advantage, is a valuable approach in the field of determination of trace elements in different foodstuffs and diets. Accordingly, various radiochemical (RNAA) and instrumental (INAA) approaches have been developed in our laboratory for the element As, Cd, Co, Cu, Hg, I, Mo, Ni, Sb, Se, Sn, Th, U, V, and others, and verified by the analysis of compositionally appropriate certified reference materials.

Rapid radiochemical neutron activation analysis for iodine in urine by different separation techniques.

In the present work on radiochemical neutron activation analysis for the determination of iodine in urine samples, the performance of three different radiochemical separation techniques, namely, direct extraction, use of an iodinated ion-exchange resin column and Schöniger combustion, were intercompared and validated. The practical advantages of the iodinated-resin technique make it most suitable for the rapid routine determination of iodine in urine. It was further verified by participation in an international intercomparison run of urine analysis, and used in a pilot study on iodine determination in the urine of 171 Slovenian schoolchildren, where it gave results in good agreement with the catalytic method.