Single derivatives for GC‐MS assay of reducing sugars and selective detection by the nitrogen‐phosphorus detector (NPD)

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Abstract
Reduction of sugar methoximes with sodium cyanoborohydride followed by permethylation with CH3SOCH2−/ICH3 affords the corresponding deoxy(methylmethoxylamino)alditol O‐methyl ethers, which are amenable to capillary gas chromatography. Derivatization proceeds under mild conditions with high yields. Only a single derivative is formed for each reducing sugar. All aldose derivatives can be separated in a single chromatographic run on glass capillaries coated with Carbowax 20 M or Superox 0.1. Good linearity was found. The introduction of the nitrogen atom in the sugar molecule makes these derivatives suitable for selective detection by the NPD. The El‐mass spectra contain intense characteristics ions at m/z 74 for aldoses and at m/z 280 for reducing disaccharides, together with a (M ‐ 15)+ion. These fragments are very suitable for highly sensitive GC‐MS analysis by selective single ion monitoring.