Determination of substances at low concentrations in complex mixtures by isotachophoresis with column coupling

A system is discussed that makes use of two PTFE narrow-bore tubes with different internal diameters. In the pre-separation narrow-bore tube, which has the larger internal diameter, a high preparation current is permitted. At a well defined distance from a conductivity detector (mounted in this pre-separation narrow-bore tube) the final separation narrow-bore tube, which has the smaller internal diameter, is coupled to the pre-separation narrow-bore tube via a T-piece. The smaller internal diameter of the final narrow-bore tube permits work at a higher current density during final separation and detection by means of conductivity and UV absorption detectors. The zones of interest can easily be separated from the sample zones, migrating isotachophoretically in the pre-separation narrow-bore tube via the detector.\u3cbr/\u3e\u3cbr/\u3eThere are several advantages over conventional isotachophoretic equipment: (i) a high sample load is permitted; (ii) the analysis time is increased negligibly; (iii) high ratios of concentrations between the sample species we permitted; and (iv) different operational systems can be applied in separation and preparation compartment

Analytical isotachophoresis

A survey is given of the latest research on isotachophoresis, especially instrumentation aspects and the application of analytical isotachophoresis. A complete scheme for the linear conductivity detector, to be used with the set of micro-sensing electrodes in direct contact with the electrolytes, is given, and a circuit for a potential gradient detector is also shown. Possible applications of analytical isotachophoresis are considered, and isotachopherograms are given in order to show the way in which information can be deduced from the apparatus described. Arbitrarily chosen examples include small anionic and cationic ionic species, amino acids, peptides and proteins. Analyses in water and deuterium oxide are compared in order to demonstrate the differences in these very similar solvents. A new pump for a counter flow of electrolyte is briefly described