LC MS/MS OF CARBOHYDRATES WITH POSTCOLUMN ADDITION OF METAL CHLORIDESUSING A TRIAXIAL ELECTROSPRAY PROBE/

A new technique for on-line postcolumn addition (PCA) formation and ta ndem electrospray mass spectrometry of carbohydrate-metal complexes is presented. A metal chloride solution is added to a carbohydrate sampl e directly within the ion source of the mass spectrometer. Using a tri axial electrospray probe, this technique can be applied to form carboh ydrate-metal complexes on-line, without the need of previously mixing the carbohydrate and metal chloride. Two basic tasks may be accomplish ed: structural analysis and sensitivity enhancement. The performance o f this approach is demonstrated through PCA of LiCl, NaCl, KCI, RbCl, CsCl, and CoCl2, introduced via the triaxial probe after chromatograph ic separation of two four-component carbohydrate mixtures. Each metal- carbohydrate complex is subsequently analyzed by on-line MS and MS/MS. This technique is used to enhance sensitivity and also, in the case o f cobalt coordination, to assist in carbohydrate structural elucidatio n. On-line LC/MS with PCA of LiCl was achieved with as little as 1.7 p mol of oligosaccharide (average consumed amount, 1.7 pmol with 1 mu L of a 10 pmol/mu L carbohydrate test mixture injection).