Anal. Chem. 2002, 74, 3434-3442
Potential Analytical Applications of Interfacing a GC to an FT-ICR MS: Fingerprinting Complex Sample Matrixes J. E. Szulejko and T. Solouki*
Chemistry Department, 5706 Aubert Hall, University of Maine, Orono, Maine 04469-5706
Details of interfacing a high-pressure gas chromatograph to the internal ion source of a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) are described. We present our preliminary results and potential analytical applications of GC/FT-ICR for analyzing complex biological and environmental sample matrixes, such as petroleum mixtures. Based on GC/FT-ICR data, rapid characterization of various automobile gasoline samples is possible. Comparison between acquired data from the GC/FT-ICR MS (in broadband mode) and a commercial GC quadrupole mass spectrometer (QMS) (over a wide mass range) indicates that sensitivity of the GC/FT-ICR MS is an order of magnitude lower. High mass resolution and mass measurement accuracy of FT-ICR MS can be utilized for unambiguous molecular formula identification of unknown analytes. Gas chromatographs (GC) have been interfaced successfully to a variety of mass spectrometers (MS), including quadrupoles, quadrupole ion traps, magnetic sectors, and time-of-flight (TOFMS) instruments,1 since ∼1960.2,3 The successful interfacing of a GC to an MS, in particular, to a Fourier transform ion cyclotron resonance MS (FT-ICR MS) must take into account of the very disparate gas flow rate requirements of the two systems. To overcome the flow rate requirements and maintain sufficiently low pressure inside the mass spectrometer vacuum chamber, several methods, either singly or in combination, have been used to interface a GC to a mass spectrometer.4,5 These methods include the use of (a) capillary columns, (b) larger vacuum pumps and improved MS vacuum housing gas flow characteristics, (c) postcolumn flow splitters, (d) molecular jet separators,( e) effusion separators, and (f) membrane separators. Details and general discussions on GC/MS interfacing have been published previously.2,3 When methods a and b are used in combination, it is possible to transfer all of the GC effluent into the MS ion source directly and without compromising the * Corresponding author. Telephone: (207) 581-1172. Fax: (207) 581-1191. E-mail:
[email protected]. (1) Pongpun, N.; Mlynski, V.; Crisp, P. T.; Guilhaus, M. J. Mass Spectrom. 2000, 35, 1105-1111. (2) McFadden, W. Techniques of Combined Gas Chromatography/Mass Spectrometry; Wiley: New York, 1973. (3) Schomburg, G. Gas Chromatography: A Practical Course; VCH Verlagsgesellschaft mbH: Weinheim, 1990. (4) Fock, W. Anal. Chem. 1975, 47, 2447-2450. (5) Watson, J. T. J. Mass Spectrom. 1998, 33, 103-108.
3434 Analytical Chemistry, Vol. 74, No. 14, July 15, 2002
performance of the MS. In methods c-f, the effluent from the GC column is split into two parts; a small fraction enters the MS ion source (∼1-5%), and the rest is pumped away. A capillary GC column may have a helium carrier gas flow rate of 2 atm mL min-1. If we assume an effective bore diameter of 6.5 cm for the ∼100 cm long vacuum chamber that houses the ICR cell,6 the pumping speed, S1, around the ICR cell is
