The reaction of the Co(II) complex with the rigid bispidine ligand L1 with two tertiary amine and two pyridine donors, [Co(II)(L1)(OH2)2]2+, with H2O2 and O2 produces [Co(II)(L2)(OH2)2]3+, where L2 is demethylated at one of the amine donors, and CH2O.

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The reaction of 3-methyl-9-oxo-7-picolyl-2,4-di(2-pyridyl)-3,7-diazabicyclo[3.

New shell-type stationary phases are widely used in fast chromatographic measurements. These columns provide more efficient separation, when applied in a conventional high-performance liquid chromatography instrument, than columns with fully porous particles, and the volume overload of core-shell particles is 60% of the value obtained for fully porous particles. Additionally, to achieve adequate sensitivity, the injection volume cannot be significantly decreased. This study presents a systematic evaluation of the possibilities of large volume injection onto columns packed with 2.6 µm Kinetex C18 shell particles. The effect of volume overload on performance of columns with different lengths (50, 100 and 150 mm) is studied. Column efficiency is compared under isocratic, pulse gradient and gradient conditions. The application of large volume injection in practice is also reported. The most suitable among the tested large volume injection techniques was the gradient elution, which was applied to determine amino acid enantiomers from fruit juice.

SummaryCapillary electrophoresis has been investigated as a novel experimental method for determination of the aggregation constants of surfactants. The tendency of sodium cholate and sodium taurodeoxycholate to associate was studied in phosphate buffers of pH 8.0 and pH 7.0, respectively. Stepwise aggregation equilibria of bile salt monomers has been described in terms of massbalance equations. The Offord equation was used to model the electrophoretic mobility of the bile salt associates, and the experimental mobility values could be fitted to the model. Interestingly, only even-membered aggregates-dimers and tetramers-besides the monomers were proposed from the results of the curve-fitting for both bile salts. The aggregation constants calculated were (in molar units): cholate log KA2 = 1.37, log KA4 = 4.98; taurodeoxycholate log KA2 = 1.68, log KA4 = 6.46. From these values, more pronounced aggregation of taurodeoxycholate starting at lower concentrations has been deduced, supporting the back-to-back association model of bile salts.