Thermospray interface advantages

The advantages and disadvantages of this type of interface, particnlarly in comparison to the moving-belt interface which was available at the same time, are listed below. This was one of the first LC-MS interfaces to be made commercially available and, although used in a number of laboratories, its development was halted premamrely by the introduction of the thermospray interface (as we shall see later). 

The next major advance in LC-MS interfacing was developed by Blakely and Vestal (55, 56). To circumvent the solvent elimination problem, Blakely et al. (55) developed the thermospray interface that operates with aqueous-organic mobile phase at typical 4.6-mm i.d. column flow rates, 1-2 mL/min. The thermospray technique works well with aqueous buffers. This feature is an advantage when the versatility of the reversed-phase mode is considered. In fact, with aqueous buffers, ions are produced when the filament is off. A recent improvement in the thermospray technique is the development of an electrically heated vaporizer that permits precise control of the vaporization (56). This... 

The obvious alternative for the in-line flow-through cell in HPLC-FTIR is mobile-phase elimination ( transport interfacing), first reported in 1977 [495], and now the usual way of carrying out LC-FTIR, in particular for the identification of (minor) constituents of complex mixtures. Various spray-type LC-FTIR interfaces have been developed, namely, thermospray (TSP) [496], particle-beam (PB) [497,498], electrospray (ESP) [499] and pneumatic nebulisers [486], as compared by Som-sen et al. [500]. The main advantage of the TSP-based... 

Confirmation by LC-MS This method is not used much, since it involves expensive apparatus, and rather good experience in the technique is needed. Abramson (66) illustrated the advantages resulting from the combination of liquid chromatography and mass spectrometry for ochratoxin A in barley. Among the types of interfaces most used for ochratoxin A analysis were thermospray, direct liquid induction (DLI), and... 

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. 

MS is becoming the detection system of choice for LC by virtue of its flexibility and high selectivity for individual solutesHowever, LC-MS is always less sensitive than GC-MS as a result of the need to transfer the analytes from the liquid phase into a high-vacuum gas phase. Other limitations of LC-MS combination include the inability to use nonvolatile buffers, the narrow optimum range for eluent flow rate influence of the proportion of organic modifier on the sensitivity, and the narrow choice of ionization methods.Nevertheless, LC-MS has been widely accepted as an advantageous choice for the determination of carbamate pesticides in water matrices, which is more robust and flexible in the absence of derivatization. Thermospray and particle-beam interfaces are probably most commonly used for offline and online determination of carbamates in Atmospheric pressure sources such as... 

For the HPLC-MS systems, many different ionization techniques have been described in the past. Various interface, ionization methods, and operating techniques applicable to LC-MS are discussed in [117J for instance Thermospray, particle beam, electrospray (ES), field desorption (FD), fast atom bombardment (FAB), time of flight (TOF), etc. The electrospray technique produces a soft ionization for thermally labile compounds, while FAB has the advantage that higher molecular mass samples can be introduced into the mass spectrometer. Table 8 offers a rough guide to the applicability of various LC-MS interfaces. For more detailed information on LC-MS, see [118]. 

The particle beam interface (Fig. 6) was created under the acronym MAGIC (monodisperse aerosol generator interface for chromatography) [28]. Now, the aerosol is produced by a variety of means (with auxiliary gas, thermospray, or ultrasonic nebulizers) at atmospheric pressure and a uniform distribution of the droplets results in particles of a narrow size distribution, which can be handled more efficiently by the separator. The droplets are dried to particles in a heated expansion chamber, and a momentum separator isolates the particles from the gas. In the source, the particles are destroyed by impact and the sample is released and ionized by using El, Cl, or even FAB. The appearance of the El spectra is almost identical to conventional El spectra obtained by direct probe or GC/MS. Therefore, library searches are possible, which is the major advantage of this interface. 

---