Journal of Chromatography, 394 (1987) 89-100 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands CHROM. 19 381 DIRECT ELECTRICALLY HEATED SPRAY DEVICE FOR A MOVING BELT LIQUID CHROMATOGRAPHY-MASS SPECTROMETRY INTERFACE GERHARD M. KRESBACH, TIMOTHY R. BAKER, ROBERT J. NELSON, JOHN WRONKA, BARRY L. KARGER and PAUL VOUROS* Barnett Institute and Department of Chemistry, Northeastern University, 360 Huntington Avenue, Boston, MA 02115 (U.S.A.) SUMMARY A direct electrically heated capillary spray device for the deposition of liquid chromatographic eluents onto a moving belt interface for liquid chromatography- mass spectrometry (LC-MS) has been constructed. This system shows significant advantages over hot propellant gas driven or cartridge heated sprayers, especially when eluents with high water content and high how-rates are used. Various param- eters have been examined to achieve optimum conditions with respect to capillary wall temperature, peak variance and analyte yield during deposition. Reversed-phase high-performance liquid chromatographic separations with standard bore columns (4.6 mm I.D.) demonstrate the enhanced possibilities of the moving belt interface for on-line high-performance LC-MS. INTRODUCTION The advantages of the moving belt interface for the combination of liquid chromatography and mass spectrometry (LC-MS) have been reported1-3. Attempts to use soft ionization techniques like secondary-ion mass spectrometry (SIMS) and fast atom bombardment (FAB) have been made 4,5. Transfer of column eluent to the surface of the moving belt with a heated gas spray device or a cartridge system results in reasonable transfer efficiency. Extra column band broadening has been shown to be low for these devices6-6. However, when used with reversed-phase high-perform- ance liquid chromatography (RP-HPLC) and standard columns (4 or 4.6 mm I.D.), either the propellant gas or the heating cartridge had to be heated to temperatures as high as 300°C. In spite of these harsh conditions the maximum throughput of aqueous eluents has been generally limited to about 0.5 ml/min with mobile phases containing more than 50% water. Thus, in order to maintain a flow of l-l.5 ml/min, required for rapid separation conditions, it has often been necessary to split off at least part of the eluent. Alternatively, for eluents with high water content, microbore columns can be used. These are not, however, always convenient, especially with standard instrumentation. In order to overcome these problems, we constructed, with inexpensive and 0021-9673/87/$03.50 0 1987 Elsevier Science Publishers B.V.