Analyse der Milch

Ohne Zusammenfassung     

New multiresidue analytical method dedicated to trace level measurement of brominated flame retardants in human biological matrices

A new method has been developed for the multi-residue measurement of the main brominated flame retardants (alpha- and gamma-hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBP-A) and polybrominated diphenyl ethers including decabromodiphenyl ether) in human biological matrices (serum, adipose tissue and breast milk). The proposed sample preparation procedure focused on reduced solvent and consumable consumption and associated procedural contamination, as well as reduced sample size. This protocol was fully validated and was proved to be suitable for identification of brominated flame retardant residues at ultra-trace level, as attested by preliminary results on real samples.     

Column selectivity in reversed-phase liquid chromatography. VIII. Phenylalkyl and fluoro-substituted columns

As reported previously, five solute-column interactions (hydrophobicity, steric resistance, hydrogen-bond acidity and basicity, ionic interaction) quantitatively describe column selectivity for 163 alkyl-silica, polar-group and cyano columns. In the present study, solute retention and column selectivity for 11 phenyl and 5 fluoro-substituted columns were compared with alkyl-silica columns of similar ligand length. It is concluded that two additional solute-column interactions may be significant in affecting retention and selectivity for the latter columns: (a) dispersion interactions of varying strength as a result of significant differences in bonded-phase polarizability or refractive index and (b) pi-pi interactions in the case of phenyl columns and aromatic solutes. These 16 phenyl and fluoro columns were also characterized in terms of hydrophobicity, steric resistance, hydrogen-bond acidity and basicity, and ionic interaction.     

Etude cristallochimique de LiPN2: Une structure derivée de la cristobalite

LiPN₂ has been prepared by reaction between Li₃N and P₃N₅ nitrides. The unit cell is tetragonal with a = 4.567(1) and c = 7.140(4) Å. The space group is $\text{I}\text{4}\text{2d}$. The structure is related to the β cristobalite type and is isostructural with CaGeN₂. It is built up from a PN₄ tetrahedra framework in the holes of which the lithium atoms are localized. The values of the rotation angle ф of tetrahedra, $\text{c}\text{a}$ ratio and θ (NPN) angle have been discussed in relation to the parameter x of the nitrogen atoms.     

Synthesis,Alkali Metal Picrate Extraction Properties,and X-Ray Crystal Structure of a Novel,Cage-Annulated Monoaza-18-Crown-6 Host

Compound 5, a cage-annulated monoaza-18-crown-6 macrocyclic polyether, has been synthesized, and its alkali metal picrate extraction capabilities have been assessed relative to those of the parent monoaza-18-crown-6 host system. It was observed that both 5 and monoaza-18-crown-6 are selective K⁺ picrate extractants; however, 5 appears generally to be a somewhat more efficient alkali metal picrate extractant than monoaza-18-crown-6. Interestingly, both the avidity and selectivity of 5 toward extraction of alkali metal picrates from aqueous solution into CHCl₃ appears to be pH dependent. In addition, the X-ray crystal structure of an unusual hydronium ion complex of 5 [i.e., 5(HCl)(H ₂ O)-(CHCl ₃ ) ₂] has been determined. The X-ray structure thus determined is compared with the corresponding structure of 5(HCl)(H ₂ O) that has been calculated via application of B3LYP Density Functional Theory.     

Deep inelastic electron scattering on light nuclei

Czechoslovak Journal of Physics -