A chemical analyzer will be reported based upon coupling liquid Ž . chromatography LC with a water mobile phase via a novel interface to high-speed Ž . capillary gas chromatography GC . The interface preserves the temporal information of the LC separation, thus a comprehensive two-dimensional LC = GC separation is obtained. The LC separation is in the 5᎐10 min range, while the GC separations are in the 1᎐2 second range. For a 5 min LC separation, 150 GC separations are obtained if the GC separations are every 2 s, thus a truly comprehensive LC = GC data density is obtained. The 100% water mobile phase simplifies instrumental requirements, thus enhancing separation and detection strategies, thus broadening the scope of LC to on-line process analysis and field monitoring applications by improving safety and minimizing waste. Volatile organic compounds are analyzed by LC = GC with enhanced chemical selectivity. Thus, this comprehensive LC = GC instrument is a useful alternative to current methods that employ headspace analysis. Separations of compounds such as benzene, Ž . toluene, ethyl benzene, o-xylene BTEX , as well as chloroform and methylene chloride are presented. Injected sample concentration limits of detection are in the 40᎐200 parts-per-billion range.