Capillary electrophoresis coupled on-line with nitrogen-selective thermionic detection using an eluent-jet interface

The on-line coupling of capillary electrophoresis (CE) with a thermionic detector (TID) originally developed for gas chromatography (GC) is reported for the first time. An eluent-jet interface previously used to combine micro-liquid chromatography and mass spectrometry can now be used to couple CE and TID. Preliminary results demonstrate the possibility of performing direct nitrogen-selective detection, even for less volatile compounds. Detection limits of 4-12 pg N/s were obtained for the four tested compounds piperidine, dimethylformamide, tetra-n-butylammonium hydroxide, and nicotinic acid. Optimization of both the TID and the eluent-jet interface can be performed independently; optimum TID parameters agree rather closely with the detector specifications under GC conditions. The nitrogen selective TID proved to be linear over more than three orders of magnitude with acceptable repeatability. The on-line coupling of CE and TID may well become an interesting approach for the rapid and direct analysis of ionic and high-molecular-mass N-containing compounds.