Ultrahigh pressure liquid chromatography/time-of-flight mass spectrometry for fast separations

Recently, ultrahigh pressure liquid chromatography (UHPLC) has been shown to overcome the pressure limitations that small particles impose on conventional pumping systems. High speed separations in UHPLC produce peak widths that range between 100 to 1000 ms, of which many are too narrow to be monitored by scanning mass spectrometers. The only mass spectrometer that is fast enough for such separations is the time-of-flight mass spectrometer (TOFMS). State-of-the-art TOFMS instruments for liquid chromatography can record and store complete mass spectra at rates as high as 100 spectra s⁻¹. In this study, high speed separations with high resolution were demonstrated using 13–15 cm×29–100 μm i.d. capillaries packed with 1.5 μm nonporous octadecylsilane- and isohexylsilane-modified silica particles utilizing a home-built UHPLC system. The UHPLC system was successfully coupled to TOFMS via a liquid-sheath electrospray interface. Separations of selected combinatorial chemistry samples, pharmaceutical compounds, and herbicides were completed in less than 100 s using UHPLC/TOFMS. Total column efficiencies ranged from 20,000–30,000 plates. The fundamental and practical aspects of UHPLC/TOFMS are discussed. Results are compared with those obtained from typical capillary LC. © 2000 John Wiley & Sons, Inc. J Micro Sep 12: 462–469, 2000