Ion-exchanger colorimetry-VIII Microdetermination of copper in natural waters

A microdetermination method for copper by ion-exchanger colorimetry has been developed. The porphyrin alpha,beta,gamma,gd-tetrakis(4-N-methylpyridyl)porphine was used as the colour reagent. After the complexation at pH 4.5 and 40 degrees , the surplus ligand was converted into the protonated species by addition of sulphuric acid. The complex and the ligand were easily sorbed on the cation-exchange resin, Dowex 50W-X2-H(+) (100-200 mesh). The resin-phase absorbances of the complex species at 424 nm and of the resin background at 510 nm were used for the measurements. There were no interferences by the foreign ions expected to be present in natural waters, at up to 1000 times the concentration of copper. With a 1 -litre sample the detection limit is 0.072 mug/l. It is possible to determine copper at mug/l. or lower levels in natural waters.     

Determination of conjugated bile acids in human urine by high-performance liquid chromatography with chemiluminescence detection.

A qualitative and quantitative analysis of the conjugated 1 beta- and 6 alpha-hydroxy bile acids, including common bile acids, in human urine using high-performance liquid chromatography with chemiluminescence detection is described. After extraction of urine with C18 silica cartridges, the bile acids were separated into non-conjugated, glycine, taurine and sulphate fractions by ion-exchange chromatography on a lipophilic gel. Solvolysis of the sulphate was carried out by treatment with trifluoroethanol in acetone containing hydrochloric acid, and the liberated amino acid conjugates were fractionated again. The individual bile acids were separated on a reversed-phase C18 column (Bile Pak II), with detection by an immobilized 3 alpha-hydroxysteroid dehydrogenase enzyme reactor and chemiluminescence reaction of the generated NADH using 1-methoxy-5-methylphenazinium methylsulphate-isoluminol-microperoxidase system. The assay method showed the detection limits ranging from 8 to 250 pmol for the bile acids tested. Analysis of urine samples obtained from newborns, non-pregnant women and women in late pregnancy showed a large difference in bile acid composition and conjugation mode, suggesting that bile acid metabolism is different during fetal and neonatal periods.     

Hankel-type operators on the space of bounded harmonic functions

We study Hankel-type operators on the space of bounded harmonic functions on the open unit disk. These operators are related to tight uniform algebras, the Dunford-Pettis property, and Bourgain algebras.

     

Rank-one commutators on invariant subspaces of the Hardy space on the bidisk

We discuss on invariant subspaces of H²(Γ²) on which .     

Preparation of substituted benzoyltrimethylsilanes by the palladium-catalyzed silylation of substituted benzoyl chlorides with hexamethyldisilane

A direct preparative route to benzoyltrimethylsilane has been found by the reaction of benzoyl chloride with hexamethyldisilane in the presence of a specified palladium(II) complex as catalyst.     

BKW-operators on the interval [0,1]

Uniqueness sets inC([0, 1]) are studied for test functions {1,t,…,t ⁿ}. As an application, we investigateBKW-operators on the interval [0,1].     

Multiple Ca(2+) environments in silicate glasses by high-resolution (43)Ca MQMAS NMR technique at high and ultra-high (21.8 T) magnetic fields

We here show the (43)Ca 5QMAS NMR spectra at high field (16.4 T) and the first 7QMAS spectrum at ultra-high field (21.8 T) for geologically important Ca-containing glasses. The high-resolution MQMAS spectra present a clear evidence of multiple Ca sites in the amorphous structures that have never been identified by other analytical methods. The present study suggests that the Ca(2+) ions are mainly in 7- and 8-fold coordination sites. This will offer valuable insights for dynamic properties of magmatic liquids. The MQMAS NMR technique at high magnetic field is a unique tool to understand the detailed structural information on a specific element in solids including organic and inorganic compounds.     

Fundamental Relation Between Entropy Production and Heat Current

Journal of Statistical Physics - We investigate the fundamental relation between entropy production rate and the speed of energy exchange between a system and baths in classical Markov processes....