DANSYLATION DERIVATIZATION ENHANCED THE DETECTION OF AMINO ACIDS BY LIQUID CHROMATOGRAPHY MASS SPECTROMETRY

High polar metabolites, containing carbohydrates, amino acids and their derivatives, and nucleosides etc, exist abundantly in plasma, urine and intracellular fluid. However, due to the poor retention on reversed-phase (RP) columns and the severe ion suppression, it is difficult to quantify these metabolites accurately by liquid chromatography mass spectrometry (LC-MS) using RP C18 columns in metabonomics studies. Derivatization is a commonly used means to improve sensitivity for specific compounds when use UV or fluorescence detectors, and was applied into LC-MS analysis currently. In this study, dansyl chloride was employed to react with amino acids. 19 amino acids were selected to evaluate the performance of dansylated amino acids by LC-MS. The results (Figure 1) showed that dansylation prolonged the retention times of amino acids on C18 column (changed from 1-9.5 min to 15-22 min) and enhanced the sensitivity markedly. Such benefits were attributed to three major factors: 1) dansylation of amino acids improved ionization efficiency; 2) dansylation of amino acids increased the hydrophobicity of compounds; 3) elution with high organic phase leaded to the greater nebulization efficiency.High polar metabolites, containing carbohydrates, amino acids and their derivatives, and nucleosides etc, exist abundantly in plasma, urine and intracellular fluid. However, due to the poor retention on reversed-phase (RP) columns and the severe ion suppression, it is difficult to quantify these metabolites accurately by liquid chromatography mass spectrometry (LC-MS) using RP C18 columns in metabonomics studies. Derivatization is a commonly used means to improve sensitivity for specific compounds when use UV or fluorescence detectors, and was applied into LC-MS analysis currently. In this study, dansyl chloride was employed to react with amino acids. 19 amino acids were selected to evaluate the performance of dansylated amino acids by LC-MS. The results (Figure 1) showed that dansylation prolonged the retention times of amino acids on C18 column (changed from 1-9.5 min to 15-22 min) and enhanced the sensitivity markedly. Such benefits were attributed to three major factors: 1) dansylation of amino acids improved ionization efficiency; 2) dansylation of amino acids increased the hydrophobicity of compounds; 3) elution with high organic phase leaded to the greater nebulization efficiency