Novel liquid chromatographic-tandem mass spectrometric methods using silica columns and aqueous-organic mobile phases for quantitative analysis of polar ionic analytes in biological fluids

Use of silica stationary phase and aqueous-organic mobile phases could sign ificantly enhance LC-MS-MS method sensitivity. The LC conditions were compa tible with MS detection. Analytes with basic functional groups were eluted with acidic mobile phases and detected by MS in the positive ion mode. Anal ytes with acid functional groups were eluted with mobile phases at neutral pH and detected by MS in the negative ion mode. Analytes poorly retained on reversed-phase columns showed good retention on silica columns. Compared w ith reversed-phase LC-MS-MS, 5-8-fold sensitivity increases were observed f or basic polar ionic compounds when using silica columns and aqueous-organi c mobile phase. Up to a 20-fold sensitivity increase was observed for acidi c polar ionic compounds. Silica columns and aqueous-organic mobile phases w ere used for assaying nicotine, cotinine, and albuterol in biological fluid s. (C) 2001 Elsevier Science B.V. All rights reserved.