Journal of Chromatography, 647 (1993) 21- 29 Elsevier Science Publishers B.V., Amsterdam CHROMSYMP. 2807 Origin of the decrease in chromatographic resolution induced by the addition of viscous matrices in liquid chromatographic-fast atom bombardment mass spectrometric systems J.P. Gagn6 and A. Carrier Regional Center for Mass Spectrometry, Department of Chemistry, University of Montreal, P.O. Box 6128, Montreal H3C 3J7 (Canada) zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA L . Varf alvy Hy dro- Q uebec, M ontreal (Canada) M.J. Bertrand* Regional Center for Mass Spectrometry, Department of Chemistry, University of Montreal, P.O. Box 6128, Montreal H3C 3J7 (Canada) ABSTRACT The monitoring of the chromatographic resolution for three pairs of analytes separated in different chromatographic systems using mobile phases with varying concentrations of viscous fast atom bombardment matrices showed that it exhibits a steady decrease with increasing matrix content in the mobile phase. The decrease in resolution is observed in the partition and ion-pair chromatographic modes at both low and high matrix contents in the eluent for both conventional and capillary chromatographic systems using precolumn addition of glycerol and thioglycerol. Careful examination of the normalized efficiency, capacity factor and selectivity terms contributing to the resolution allowed the identification of the sources of the decrease in resolution in the presence of a matrix in the eluent. The efficiency and capacity factor terms show decreases with increasing matrix content in all systems. Subtle variations in the selectivity term observed in the presence of a viscous matrix can increase or limit the decrease in resolution. The variations observed for the efficiency term show similar trends in all systems studied and appear to be independent of the analyte or the chromatographic mode. However, the variations in capacity factor and selectivity induced by the presence of the viscous matrix are dependent on the nature of the analyte, the type of chromatography and the nature of the matrix. INTRODUCTION The technique of continuous-flow fast atom bombardment mass spectrometry (CF-FAB-MS) is a powerful tool that allows repetitive and rapid determinations of polar and labile compounds in aqueous media. In complex mixture analysis, * Corresponding author. however, this technique used alone can suffer from ionization suppression and insufficient res- olution capability [1,2]. In order to reduce these limitations, coupling of this technique with liquid chromatography (LC-FAB-MS) is often a way to gain supplementary temporal resolution which allows the efficient operation of the mass spec- trometric system. As the presence of a viscous matrix is necessary to optimize ionization in 0021-9673/93/$06.00 @ 1993 Elsevier Science Publishers B.V. All rights reserved