RESUMO
A method is proposed for the determination of pterins in urine without clean-up by reversed-phase high-performance liquid chromatography on a C18 column previously conditioned with cetyltrimethylammonium bromide. Other endogenous compounds are retained in the column, preventing interference. Xanthopterin, neopterin, isoxanthopterin, monapterin, biopterin, 6-hydroxymethylpterin, pterin and lumazine can be determined. Retention and separation mechanisms are discussed.
Assuntos
Pterinas/urina , Cetrimônio , Compostos de Cetrimônio , Fenômenos Químicos , Química , Cromatografia Líquida de Alta Pressão , Humanos , Concentração de Íons de Hidrogênio , Indicadores e Reagentes , Espectrometria de FluorescênciaRESUMO
A potentiometric permanganate titration has been developed for the determination of hydrogen peroxide in the presence of fluoride, as well as of the peroxide content in the titanium-fluoride-peroxide mixed complex. It is based on the stabilization of manganese(III) with an excess of fluoride in a moderately acidic medium (pH close to 3) and on the use of iron(III) as catalyst. Errors are less than 0.5%.
RESUMO
An accurate method for routine determination of silica in silicate materials is proposed. It is based on the decomposition of the silicate materials with LiCO(3)/H(3)BO(3) flux, stabilization of the silica with fluoride, and the use of a suitable calibration, measurement and computation pattern.
RESUMO
A rapid method for sample decomposition of silicate rocks and further accurate determination of major elements by atomic-absorption spectrometry is described. The solutions obtained were stabilized so that the measurements were comparable with those made on standard rocks solutions. Interferences were avoided. The most important methods of silicate rock decomposition were applied, and the useful characteristics from each were combined, and in some cases improved, to obtain the final procedure.
