Direct-liquid-introduction interface mobile phases

It is much more difficult to couple HPLC on-hne with El and Cl sources (Ardrey 2003) since the voliune of vaporized mobile phase is up to 10 times larger than that of the liquid, far beyond the pumping capabilities of any realistic vacuum system unless the flow rate is restricted by a post-column split to a few xL.min, as in the so-called direct liquid introduction interfaces (Abian 1999) for Cl and (less commonly) El these interfaces... 

LC-MS inlet probes support all conventional HPLC column diameters from mobile phase must be eliminated, either before entering or from inside the mass spectrometer, so that the production of ions is not adversely affected. The problem of removing the solvent is usually overcome by direct-liquid-introduction (DLI), mechanical transport devices, or particle beam (PB) interfaces. The main disadvantages of transport devices are that column... 

Direct liquid introduction (DLI) methodology has been described elsewhere (9). A thermospray probe and source (TSP, Model TS 360Q) were acquired from Vestec Corp. (Houston, TX) and later modified to include a probe tip heater incorporated in a copper block. Because of thermal contact, however, there was considerable interaction between the source temperature, the probe tip temperature and the temperature of the capillary. For this reason, attempts to optimize the ion currents by adjusting temperatures had limited success. Typical temperatures of the tip of the interface were 199- 205°C with source temperatures of230-240°C. The two mobile phases used were 0.1M ammonium acetate and 4 1 (v/v) 0.1 M ammonium acetate acetonitrile. The flow rate was 1.0 ml/min 1. Samples were admitted to the TSP probe via a Rheodyne (Model 7125) valve. 

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