Counterion Exchange Selectivity in Detergent–Polymer Aggregates

In aqueous solution, the interaction between sodium dodecyl sulfate (SDS) and poly(ethylene glycol) (PEG) results in the formation of small aggregates or clusters of SDS attached to the PEG polymer chain. Selectivity coefficients for exchange of two monovalent (N-methyl-4-cyanopyridinium cation and Tl⁺) and two divalent (methylviologen cation and Cu²⁺) counterions at the surface of SDS–PEG clusters, determined employing photophysical techniques, are similar, but not identical, to those for exchange at the surface of SDS micelles in the absence of PEG. The principal factor affecting ion exchange selectivity in SDS–PEG clusters does not appear to be aggregate size or surface charge density but rather the presence of poly(oxyethylene) subunits at the aggregate surface.     

The determination of certain major and minor elements in geological samples by inductively coupled plasma atomic emission spectrometry. Some interference problems with the analysis of geological standard reference materials and nutrition supplements

Direct ICP-AES measurements of the digested geological standard reference material samples yielded the wrong information about their composition. The differences between certified and measured concentrations of the samples were due to the complicated sample matrix. The measured concentrations can be successfully corrected by using a multiple linear regression technique. The correction is based on the multiple regression line calculated from the analytical results at synthetic mixtures of matrix elements, where concentrations varied on five levels. There were no significant (P = 0.05) differences between certified and measured concentrations in standard reference materials after the correction. The same method was used in the analysis of nutrition supplements. Received: 25 January 2000 / Revised: 15 March 2000 / Accepted: 31 March 2000     

Alcoyl-gluco-alcaloides: nouveaux composes isoles de pauridiantha lyalii brem (rubiacees)

La structure destrans fe´ruloyl-6′ ettrans sinapoyl-6′ lyaloside, isole´s des feuilles dePauridiantha Lyalii, ae´te´de´termine´e par de´gradation chimique et par spectroscopie (Masse, RMN¹H et¹³C). Ces compose´s font partie d'un groupe structural caracte´rise´par un enchai?nement alcaloide-monoterpe`ne-ose-acide (C<sub>6</sub>-C<sub>3</sub>), groupe dont un seul repre´sentant semble avoire´te´isole´jusqu'a`pre´sent. Leur fonction dans le ve´ge´tal est discute´e.     

Eine Beurtheilung der L?slichkeit einiger schwer l?slicher K?rper aus der elektrischen Leitungsf?higkeit der L?sungen

Ohne Zusammenfassung     

Ueber die quantitative Bestimmung des Uranoxyds

Ohne ZusammenfassungVom Verfasser mitgetheilt.     

Ueber die Zerlegung des Quecksilberjodids

Ohne ZusammenfassungVom Verfasser mitgetheilt     

Mikrochemie

Ohne Zusammenfassung