Flame atomic absorption spectrometric method for the determination of beryllium in natural waters after separation with N-benzoyl-N-phenylhydroxylamine.

A procedure for the determination of beryllium in natural waters is proposed. A solvent extraction step was performed in order to overcome interferences and isolate beryllium before it was atomized by direct nebulization of the organic phase in a dinitrogen oxide-acetylene flame. N-Benzoyl-N-phenylhydroxylamine was used as the extractant whilst isobutyl methyl ketone was the organic solvent. The effects of pH, amine concentration in the organic phase, shaking time, stability of the complex and nature of the extracted species were studied. The detection limit and linear response range are 2 ng ml-1 and 0-1.0 microgram ml-1, respectively. The result obtained for a standard reference material compared well with the quoted value.

Interactions of cephalosporins and penicillins with nonpolar octadecylsilyl stationary phase.

The capacity factors of several penicillins and cephalosporins, as well as those of 7-aminocephalosporanic acid, 6-aminopenicillanic acid, and 7-aminodeacetoxycephalosporanic acid, were determined at pH 2.5-7.5 with different methanol concentrations in the mobile phase. The influence of ionic strength on activity factors also was studied. Some theoretical equations providing a quantitative description of the influence of the mobile phase pH on the retention of penicillins and cephalosporins by an octadecylsilyl stationary phase were established. The analysis of experimental data by a nonlinear least-squares fit to theoretically deduced equations permitted determination of the capacity factors of anionic, cationic, zwitterion, and undissociated forms of the substances studied.