Fast and simple droplet sampling of sap from plant tissues and capillary microextraction of soluble saccharides for picogram-scale quantitative determination with GC-MS

Soluble saccharides are very important metabolites of the life cycle and synthesis of structural polysaccharide components (cellulose, hemicellulose, pectin, etc.) of cell walls. A new method for droplet sampling of saps from tissues of organisms and manipulation routines in capillaries for extraction, derivation, and partitioning were developed for picogram-scale quantitative determination with gas chromatography-mass spectrometry (GC-MS). Five to ten microliters of sap was sampled with a glass capillary containing ribitol (internal standard). Subsequently, the analytes were acetylated with acetic anhydride and catalyzed by 1-methylimidazole. Finally, the soluble saccharides were qualitatively detected with GC-MS SIM (selective ion monitoring) mode. The linear ranges of the method were up to 1×10(-6) mol/L and the theoretically lowest limits of detection (LOD, s/n≥3) were up to 1×10(-9) mol/L. The method is suitable and applicable to analysis of soluble monosaccharides in fresh tissues and other aqueous samples in wide fields of agriculture, food science, biological sciences, and even medical studies.