W. Y. Feng

Study of chemical speciation of trace elements by molecular activation analysis and other nuclear techniques

The information on the chemical speciation of trace elements in biological and environmental systems is much needed to evaluate their biological and environmental significance. Albeit a number of atomic behavior-based analytical techniques are available for the analysis of chemical speciation of trace elements, nuclear analytical techniques, especially the molecular activation analysis method, can in many cases play a unique role. This review describes the methodology, merits and limitations of nuclear analytical techniques for chemical speciation study in biological and environmental samples. The emphases are focused on the chemical species and the environmental and biological significance of rare earth elements in natural plants and human liver, selenium in a mammalian organism, mercury in rat brain and liver, chromium in rat organs and Cr-rich yeast, organohalogens in pine needles and marine organisms, and iodine in sea-water, soil, atmosphere, marine plants and the thyroid gland for demonstration of the features of nuclear analytical techniques. The future perspectives of nuclear analytical techniques for the study of chemical species of trace elements will be briefly outlined as well.

Determination of Chromium Combined with DNA, RNA and Proteins in Chromium-Rich Brewer's Yeast by NAA

The content of chromium in the DNA, RNA and protein fractions separated from chromium-rich and normal brewers yeast was determined by neutron activation analysis (NAA). Our results show that the extracted relative amounts and concentrations of DNA, RNA and proteins have no significant difference for two types of yeast, but the chromium content in DNA, RNA and proteins fractions extracted from the chromium-rich yeast are substantially higher than those from the normal. In addition, the concentration of chromium in DNA is much higher than that in RNA and proteins. It is evident that the inorganic chromium compounds can enter the yeast cell during the yeast cultivation in the chromium-containing culture medium and are converted into organic chromium species, which are combined with DNA, RNA and proteins.

A preliminary study of chromium distribution in chromium-rich brewer’s yeast cell by NAA

The purpose of this study was to assess the chromium (Cr) distribution in chromium-rich brewer’s yeast cell. The chromium concentrations in the cell wall and protoplast fractions of the chromium-rich yeast were determined by neutron activation analysis (NAA). Moreover, the combined state of chromium and amino acid content in the Cr-rich brewer’s yeasts was analyzed and measured. The experimental results indicate that the introduction of water-soluble chromium (III) salt as a component of the culture medium for yeasts results in a substantial amount of chromium absorbed through the cell wall by the yeast, among which 80.9% are accumulated in the protoplast. It implies that, under optimal conditions, yeasts are capable of accumulating large amounts of chromium and incorporating chromium into organic compounds.

Study on the metabolism of physiological amounts of Cr(III) intragastrical administration in normal rats using activable enriched stable isotope Cr-50 compound as a tracer

In order to study the metabolism of physiological amounts of51Cr (10 μg/100 g of body wt.) intragastrically administered in rats, the activable enriched stable isotope Cr-50 compound Cr2O3 was used as a tracer. The absorption and distribution of51Cr(III) in rats with time were studied. Significant51Cr contents were found in all the organs and tissues of interest. The kidney, liver and bone contain higher amounts of51Cr than others. The fact that specific activities of51Cr are notably high in kidney, bone, spleen and pancreas and decrease gradually with time suggests that there are tighter binding of chromium in these organs. The excretion of51Cr at various time intervals was also studied. Almost totally intragastrically administered dose was excreted in the feces. The increased urinary excretion of51Cr with time indicates that the urine-chromium is the metabolic derivative of organism. In view of the tissues distribution and excretion, it can be concluded that no more that 1% of the dose was absorbed from the gastrointestinal tract.

Study of Chromium Speciation in Normal and Diabetic Rats by Activable Enriched Stable Isotope Technique

Chromium speciation was investigated in the liver cytosol, serum and urine of normal and diabetic rats after a single intravenous injection of enriched stable isotope 50Cr tracer solution. Sephadex G-25 gel chromatography combined with instrumental neutron activation analysis was used to isolate and characterize protein-bound chromium in the above materials. The results indicate that Cr is mainly combined with a high-molecular-weight protein either in liver cytosol or serum. A low-molecular-weight, Cr-containing compound (LMWCr) was found in all the observed liver, serum and urine samples of both normal and diabetic rats. Chromium is excreted chiefly as LMWCr in urine.