Thermospray universal interface

The new Thermospray "Universal Interface" was been developed to allow HPLC to be properly coupled to conventional El and Cl mass spectrometry. A block diagram of the new interface is shown in Figure 1. The LC effluent is directly coupled to a Thermospray vaporizer in which most, but not all, of the solvent is vaporized and the remaining unvaporized material is carried along as an aerosol in the high velocity vapor jet which is produced. The operation and control of the thermospray device has been described in detail elsewhere. (1)... 

A new universal interface and combination ion source is described which allows choice of ionization modes among electron impact (El), chemical ionization (Cl), and Thermospray. Results obtained with this system on a Vestec Model 201 LC-MS are presented for some test compounds and some environmentally important compounds on the Appendix VIII list. The relative advantages of the different ionization modes for compound identification and quantitation are discussed and data are presented on the performance of the system. 

Recent advances in electrospray ionization (ESI), atmospheric-pressure chemical ionization (APCI), thermospray, and particle beam LC-MS have advanced the analyst toward the universal HPLC detector, but price and complexity are still the primary stumbling blocks. Thus, HPLC-MS remains expensive and the technology has only recently been described. Early commercial LC-MS uses particle beam and thermospray sources, but ESI and APCI interfaces now dominate. Liquid chromatography MS can represent a fast and reliable method for structural analyses of nonvolatile compounds such as phenolic compounds (36,37), especially for low-molecular-weight plant phenolics (38), but the limited resolving power of LC hinders the widespread use of its application for phenolics as compared to GC-MS. 

In the late 1980s, thermospray ionization (TSI) techniques offered what would be the precursor to a universal and reliable LC/MS interface for compounds of pharmaceutical interest. Conventional HPLC flow rates (l-2mL/min) were accommodated by this interface, using volatile buffers that contain ammonium acetate. New applications were realized, and higher standards of analytical performance were established for pharmaceutical analysis (Voyksner et al., 1985 Beattie and Blake, 1989 Oxford and Lant, 1989 Malcolm et al., 1990 Bowers et al., 1991). 

Mass spectrometers Interface dependent Interface dependent Universal, within limits imposed by interface Complex, expensive devices highly dependent on an efficient interface electrospray and thermospray interfaces are most common linear response is difficult to achieve... 

MS is undoubtedly the solution of the near future for LC detection. Improvements made to interfacing devices together with a continuous and sensible diminution of instrumentation costs promote MS as a universal/selective tunable detection system. Atmospheric pressrue electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) are the most robust and popular devices for interfacing MS to LC systems. In Table 9, LC-MS data for some pesticides are given. Although ESI and APCI are more often used, other LC-MS interfaces produce reliable results in pesticide applications thermospray (TSI), particle beam (PBI) and matrix-assisted postsource decay laser desorption/ionization (CID-PSD-MALDI). 

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