Fast ultrahigh-pressure liquid chromatography: On-column UV and time-of-flight mass spectrometric detection

An ultrahigh-pressure liquid chromatography (UHPLC) system capable of gener ating 52,000 psi (3,600 bar) was constructed. Fused-silica capillaries with inner diameters of 29 mu m and lengths up to 70 cm were packed with nonpor ous 1.5-mu m isohexylsilane-modified (C-6) silica particles using a carbon dioxide enhanced slurry packing method. The system performance was evaluate d by monitoring the UV absorbance of small organic compounds on-column. At optimum linear velocity, efficiencies as high as 570,000 plates m(-1) (k = 0.5) were obtained. Analysis times could be reduced significantly, both by operating at higher than optimum linear velocities and by shortening the co lumn. Selected benzodiazepines and triazine herbicides were separated in le ss than 60 s. The UHPLC system was also coupled to a time-of-flight mass sp ectrometer for the separation and detection of selected benzodiazepines. A loss in efficiency due to the liquid sheath interface was observed. (C) 199 9 John Wiley & Sons, Inc.