Thermospray interface probe temperature

The results were obtained with an ESA coulometric cell which was coupled via a Vestec thermospray interface to a Finnigan MAT TSQ 4500 triple quadrupole mass spectrometer with an INCOS data system. The coulometric cell had a volume of 5 pL, a 12 cm reticulated vitreous carbon working electrode, and palladium counter and reference electrodes. The thermospray probe tip and source block temperatures were 250 and 290 C, respectively. In EC/TSP/MS/MS analysis, the mobile phase was 0.1 M ammonium acetate (pH "7), at a flow rate of 2.0 mL min". Twenty five pL of a 300 pM solution were injected. 

Principles and Characteristics Thermospray ionisation (TSP) involves introduction of a relatively high flow (0.2-2mLmin ) of solvent into the ion source of a mass spectrometer, and is therefore suitable as an interface for HPLC-MS, using standard bore columns. A vaporiser probe (essentially a resistively heated capillary tube of about 100 xm i.d.) acts as a transfer line for taking solvent and solute into the source. The source is heated to prevent condensation of the solvent, and the temperature of the capillary is chosen so as to ensure vaporisation of the solvent. In this way, a vapour jet is generated, which contains small, electrically charged droplets if the solvent is at least partially aqueous and... 

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. 

---