Moving-belt interface mass spectrometry

P. Arpino, Combined liquid chromatography mass spectrometry I Coupling by means of a moving belt interface. Mass Spectrom. Rev. 8, 35-55 (1989). 

Reference has been made to the problems associated with the presence of highly involatile analytes. Many buffers used in HPLC are inorganic and thus involatile and these tend to compromise the use of the interface, in particular with respect to snagging of the belt in the tunnel seals. The problem of inorganic buffers is not one confined to the moving-belt interface and, unless post-column extraction is to be used, those developing HPLC methods for use with mass spectrometry are advised to utilize relatively volatile buffers, such as ammonium acetate, if at all possible. 

Perhaps the most mechanically complex solution ever developed for uniting HPLC with mass spectrometry was the moving belt interface [54]. The heart of this system was a mechanically driven continuous belt (analogous to an escalator or moving walkway) to which the HPLC eluent was applied. The majority of the mobile phase was evaporated by a heat source (ideally hot enough to vaporize the solvents but not to... 

D.E. Games, P. Hirter, W. Kuhnz, E. Lewis, N.C.A. Weerasinghe and S.A. Westwood, Studies of combined liquid chromatography-mass spectrometry with a moving-belt interface, J. Chromatogr., 203 (1981) 131-138. 

Coupling of liquid chromatography to mass spectrometry has not only led to a wide variety of interfaces, but also initiated the development of new ionization methods. [8-13,62] In retrospect, the moving belt interface seems rather a curiosity than a LC-interface. The LC effluent is deposited onto a metal wire or belt which is heated thereafter to desolvate the sample. Then, the belt traverses a region of... 

Games, D. E. McDowell, M. A. Levsen, K. Schafer, K. H. Dobberstein, P. Gower, J. L. 1984. A comparison of moving belt interfaces for liquid chromatography mass spectrometry. Biomed. Mass Spectrom., 11, 87-95. 

Hayes,M. J. Lankmayer,E. P. Vouros,P. Karger,B. L. McGuire, M. 1983. Moving belt interface with spray deposition for liquid chromatogra-phy/mass spectrometry. Anal. Chem., 55,1745-1752. 

Over 30 years of liquid chromatography-mass spectrometry (LC-MS) research has resulted in a considerable number of different interfaces (Ch. 3.2). A variety of LC-MS interfaces have been proposed and built in the various research laboratories, and some of them have been adapted by instmment manufacturers and became commercially available. With the advent in the early 1990 s of interfaces based on atmospheric-pressure ionization (API), most of these interfaces have become obsolete. However, in order to appreciate LC-MS, one carmot simply ignore these earlier developments. This chapter is devoted to the older LC-MS interfaces, which is certainly important in understanding the histoiy and development of LC-MS. Attention is paid to principles, instrumentation, and application of the capillary inlet, pneumatic vacuum nebulizers, the moving-belt interface, direct liquid introduction, continuous-flow fast-atom bombardment interfaces, thermospray, and the particle-beam interface. More elaborate discussions on these interfaces can be found in previous editions of this book. 

Combined liquid chromatography/mass spectrometry (LC/MS)can play an important role in both qualitative and quantitative bioanalysis. LC/MS can be performed with a number of interfaces. Three interfaces are presently available in our laboratories i.e., the thermospray interface (TSP), the moving-belt interface (MBI), and continuous-flow fast atom bombardment (CF-FAB). These interfaces are supplementary with respect to their applicability and the type of information that can be obtained. 

MS has been used with LC (moving belt interface), though not as extensively as with GC. Atmospheric pressure chemical ionization and pneumatically assisted electrospray mass spectrometry coupled to LC have been used for PAC analysis. Since it is easy to collect fractions continuously from LC, bioassays of the collected fractions can be performed and a muta-chromatogram (a plot of mutagenic potency versus fraction number) obtained. 

Jungalwala, F. B., Evans, J. E., Kadowaki, H. and McCluer, R. H. (1984) High performance liquid chromatography-chemical ionisation mass spectrometry of sphingoid bases using moving-belt interface. J. Lipid Res., 25, 209-16. 

Games, D. E., 1981, Combined liquid chromatography-mass spectrometry with a moving-belt interface, in Soft Ionisation Biological Mass Spectrometry (H. R. Morris, ed.), pp. 54-68, Heyden and Son, London. 

SEC suffers from poor resolution and low sensitivity [5], while GC is limited by the high molecular weight and polar nature of many antioxidants and light stabilisers, which are designed to be reactive and so decompose when exposed to heat [9]. HPLC the most widely used instrumental method also has limitations [10-12]. HPLC lacks a simple sensitive universal detector that is compatible with all liquid mobile phases. UV or fluorescence detectors, which are commonly used, require that additives have a chromophoric moiety, while the universal refractive index detector only functions under isocratic conditions. As a result, Vargo and Olson have coupled HPLC with mass spectrometry (MS) for this type of application by using a moving belt interface [13]. 

Games, D.E. Hirter, P. Kuhnz, W. Lewis, E. Weerasinghe, N.C.A. West-wood, S.A. Studies of Combined Liquid Chromatography-Mass Spectrometry With a Moving-Belt Interface. J. Chromatogr. 1981,203, 131-138. 

All gas chromotography/mass spectrometry (GC/MS) analyses of monomers and intermediates were performed on a Finnigan 1020 GC/MS using a 30-m RSL-150 fused silica capillary column. Liquid chromatography/mass spectrometry (LC/NS) was performed on a Finnigan 4500 mass spectrometer using acetonitrile-water eluent and a moving belt LC/MS interface. 

The scientific curiosity to explore the utility of mass spectrometry to compounds that could not be analyzed by conventional GC/MS was supported by the need to extend the technique into the expanding field of biochemistry. While the development of LC/MS is still undergoing rapid evolution as evidenced by the number of reviews published at regular intervals, three main technological approaches have been constructed which continue to gain popular acceptance for practical use. These three introduction interfaces that are available commercially are the moving belt or transport interface (MB1), direct liquid introduction (DLI), and thermospray (TSP). This review will concentrate on these three interface types that are currently in widespread use. 

The two chapters that were selected for this topic one on GC-ion trap mass spectrometry, by SabUer and Fujii and the other by Schroder on LC-MS in environmental analysis give an excellent contribution to the application of GC-MS and LC-MS to environmental analysis. Both chapters include many practical aspects and examples in the environmental field and also cover the historical perspective of the techniques and show the perspective on ionisation and scanning modes. Advances achieved in GC-ion trap by the use of external ion sources and GC/MS/MS possi-bihties are discussed. The LC-MS chapter provides an overview of the first applications of LC/MS interfacing systems, such as moving belt, direct Uquid introduction (DLI) and particle beam (PB), and then on the more recent soft ionisation techniques, like thermospray and atmospheric pressure ionisation interfacing systems. 

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