On-line capillary electrophoresis with mass spectrometry detection for the analysis of carbohydrates after derivatization with 8-aminonaphthalene-1,3,6-trisulfonic acid

Capillary electrophoresis (CE) with mass spectrometry (MS) detection is an ideal tool for analytical use, which combines a nano quantity assay with mass determination. Carbohydrate analysis has always been a challenge because of the inherent structural complexity and the lack of a chromophore, unless derivatization is used. Here we use the derivatization of carbohydrates with a fluorophore, 8-aminonaphthalene-1,3,6-trisulfonic acid (ANTS). This chromophore has two advantages, first, it facilitates UV and fluorescence detection and, second, it introduces negative charge to the analyte, which enhances zone electrophoretic separation. In this study, CE combined with negative ion electrospray MS (ESI-MS) was evaluated for the on-line analysis of ANTS labeled carbohydrates and cellulose fragments. The CE system was connected to the MS by a sheath-liquid electrospray arrangement. The ANTS reagent and Dextrin-15, which contains oligomers of maltose, were used as model samples for ESI-MS optimization in flow-injection–MS and CE–MS modes, respectively. Various sheath-liquid compositions regarding organic modifier (isopropanol, methanol, or acetonitrile) and electrolyte (acetic acid–formic acid, ammonium acetate, or triethylamine) were studied. The response as well as the analyte charge state distribution was found to be dependent on the composition and the orifice voltage. Low-pH conditions with isopropanol as organic modifier were sensitive, stable, and the most favorable for analysis.