A chemical catalytic method for determination of silver in human saliva.
Abstract A catalytic method for the determination of silver in saliva is suggested. Silver was determined by a very simple technique in concentrations in saliva higher than 1 μg/100 ml with a coefficient of variation of 5.7 per cent. The method was used to investigate the correlation between some pathogalvanic phenomena connected with the presence of amalgam restorations in the oral cavity and the concentration of silver in saliva. The application of the method showed no correlation between the number of restorations and the silver concentration in saliva. The joint effects of restorations, their corrosion potential and the concentration of silver in saliva were correlated with the occurrence of unpleasant sensations in the mouth.
Routine catalytic determination of trace amounts of cobalt in small urine samples
The oxidation of catechol by hydrogen peroxide, catalyzed by cobalt(II), is a highly sensitive and selective reaction. It makes it possible to analyze a small sample of urine (5.0 ml) for cobalt without the need for isolation of the analyte from the matrix. The sample is dried and dry-ashed according to a temperature programme, and the residue is dissolved in hydrochloric acid. After filtration of the solution, acetate buffer and sodium citrate are added and cobalt is determined catalytically in an aliquot of the solution, by the standard-addition method.
Photoinduced spin-state transition of Co3+ in the layered perovskite manganite thin film
The photoinduced effect, at different temperatures, on layered perovskite manganite La1.2Sr1.8Mn1.8Co0.2O7 thin film deposited on a SrTiO3(100) substrate has been studied using a He–Ne laser (632.8 nm) with the power of output 25 mW at low temperatures. The electrical transport and magnetic properties of the film are investigated systematically in the temperature region from 20 to 300 K. The resistance shows a significant decrease at low temperatures (T<90 K) under laser irradiation, which can be interpreted in terms of the spin-state transition of Co3+ ions. The magnetic field combined with the laser is also used to detect the photoinduced effect of the spin-glass state. The time dependence of the metastable system under several applied fields was also discussed. The system has the ability to keep a persistent memory of the magnetic history imprinted in its zero-field resistance.