ISOTACHOPHORETIC DESORPTION OF ANIONIC COMPOUNDS FROM SOLID-PHASE ADSORBENTS

The isotachophoretic (ITP) desorption of anionic compounds adsorbed on solid-phase extraction (SPE) columns is described. Octadecyl (C-18)-modified silica and styrene-divinylbenzene (ST-DVB) packings were used as the SPE adsorbents. The influence of methanol on the ITP desorption of the test compounds was also examined. The ITP desorption of amaranth red as the test compound from both the ODS and ST-DVB adsorbents showed good results. In contrast, the ITP desorption of bromophenol blue resulted in a discontinuous desorption and no sharp zones were obtained. However, the addition of methanol to both the leading and terminating electrolytes during the ITP desorption in combination with a counter flow improved the desorption of bromophenol blue significantly. The ITP desorption of benzoic acid from the ST-DVB phase showed no reproducible results, whereas its desorption yields from the ODS phase was significantly better.