Zdeněk Friedl

Ampholytic dyes for spectroscopic determination of pH in electrofocusing

Abstract Ampholytic dyes were studied for the purpose of spectroscopic monitoring ofthe local pH of solutions within capillary systems used for the focusing and separation of ampholytes. The dyes are compounds selected from previously described aminomethylnitrophenols and also a group of compounds based on aminomethylated sulfonphthaleins. The suggested ampholytic dyes are good ampholytes and are also pH indicators with colour transition around the p I value. The possibility of the spectroscopic monitoring of actual pH was verified in a system involving pH gradient ion chromatography with diode-array detection and on-line flow-through pH detection.

Capillary isoelectric focusing with UV-induced fluorescence detection.

Low-molecular-mass fluorescent compounds excitable in the near UV region with suitable acidobasic and electrophoretic properties are suggested as isoelectric point (pI) markers for isoelectric focusing (IEF) with UV photometric and UV excited fluorometric detection. The experimental set-up of capillary IEF with UV excited fluorometric detection and properties of new UV-induced fluorescent pI markers are given. The pI values of 18 new pI markers determined independently of IEF methods range from 2.1 to 10.3. The examples of separation of new pI markers together with derivatized proteins by capillary IEF with photometric or fluorometric detection are presented.

Extraction and determination of trinitrotoluenes and products of their biotransformation in soil samples

The separation of a mixture of trinitrotoluenes (TNTs) and their metabolites by reverse phase liquid chromatography using different columns with octadecyl stationary phase is presented. The retention behaviour of a mixture of TNTs and their metabolites was studied under different chromatographic conditions. The mixture of methanol/water was used as a mobile phase in isocratic and gradient modes. The effect of content of organic modifier and temperature of mobile phase has been investigated. Very good RP-HPLC separation of 14 nitroaromatic compounds was obtained using stepped gradient elution. Different properties of extraction procedures for isolation of trinitrotoluenes and their metabolites from soil were tested. Experimental conditions of Soxhlet warm extraction (extractant type, extraction time) suitable for efficient extraction of individual analytes were studied. Recoveries over 80% for all studied compounds and over 90% for almost all (11 compounds) were obtained in short extraction time (1 hour). The formation of precipitate during the Soxhlet extraction was observed and the further treatment of extract was necessary. The amount of precipitate formed from an artificial soil was higher than that from a natural one. THF was found as the best solvent suitable for total dissolution of precipitate.