Quantitation of low molecular weight sugars by chemical derivatization-liquid chromatography/multiple reaction monitoring/mass spectrometry

A new method for the separation and quantitation of 13 mono- and disaccharides has been developed by chemical derivatization/ultra-HPLC/negative-ion ESI-multiple-reaction monitoring MS. 3-Nitrophenylhydrazine (at 50 degrees C for 60 min) was shown to be able to quantitatively derivatize low-molecular weight (LMW) reducing sugars. The nonreducing sugar, sucrose, was not derivatized. A pentafluorophenyl-bonded phase column was used for the chromatographic separation of the derivatized sugars. This method exhibits femtomole-level sensitivity, high precision (CVs of <= 4.6%) and high accuracy for the quantitation of LMW sugars in wine. Excellent linearity (R-2 >= 0.9993) and linear ranges of similar to 500-fold for disaccharides and similar to 1000-4000-fold for monosaccharides were achieved. With internal calibration (C-13-labeled internal standards), recoveries were between 93.6% +/- 1.6% (xylose) and 104.8% +/- 5.2% (glucose). With external calibration, recoveries ranged from 82.5% +/- 0.8% (ribulose) to 105.2% +/- 2.1% (xylulose). Quantitation of sugars in two red wines and two white wines was performed using this method; quantitation of the central carbon metabolism-related carboxylic acids and tartaric acid was carried out using a previously established derivatization procedure with 3-nitrophenylhydrazine as well. The results showed that these two classes of compounds-both of which have important organoleptic properties-had different compositions in red and white wines.