Carboxyl-Based CPMP Tag for Ultrasensitive Analysis of Disaccharides by Negative Tandem Mass Spectrometry.

Here, we develop a sensitive method for glucose-containing disaccharide analysis by 1-(4-carboxyphenyl)-3-methyl-5-pyrazolone (CPMP) derivatization using mass spectrometry. The intense anion of [M - H] - ( m / z 759) was observed for CPMP-labeled disaccharides in a negative mode. After derivatization, its sensitivity was significantly increased with the limits of detection (LODs) and limits of quantification (LOQ) ranging from 3.90 to 8.67 ng L -1 and 12.99 to 28.92 ng L -1 , respectively. During CID-MS/MS analysis, the fragment patterns of CPMP derivatized disaccharides in the negative mode were simpler and clearer than their counterparts in a positive mode, which further could be applied to distinct and relatively quantitative isomeric disaccharides with ultrahigh sensitivity and good reproducibility. The great linear relationships could be achieved under wider concentration ratios from 0.01 to 20 compared to the previous report. Eventually, the developed methodology was applicable to identify isomeric disaccharides in beers. No sucrose was discovered. All beers contain 1,4- and 1,6-linked disaccharides. Some of them also have a mixture of 1,2- and 1,3-linked disaccharides. Through the integration of statistical analysis, beers with different production processes were finally discriminated, and the relative quantification of isomaltose and maltose was realized. In general, this method is sensitive, fast, and reliable for the discrimination and relative quantification of isomeric disaccharides in complex matrices. This study provides a new idea for the structural analysis of oligosaccharides in food, plants, and animals and an important theoretical basis for the exploration of new functions of oligosaccharides.