A Rapid Modified Method for Compositional Carbohydrate Analysis of Lignocellulosics by High pH Anion-Exchange Chromatography with Pulsed Amperometric Detection (HPAEC/PAD)

Abstract

During the last decade, high pH anion exchange chromatography with pulsed amperometric detection (HPAEC/PAC) has gained increasing acceptance as the method of choice for analysis of neutral sugars commonly occurring in woods, pulps, and other lignocellulosics. This paper describes modified chromatographic conditions and discusses other critical factors that improve the precision and efficiency of this application. The method involves a controlled loading of acetate onto the column prior to equilibration with water and injection of sample. In-line solid-phase extraction is used to remove hydrophobic substances that have the potential to foul the analytical column. Critical operational parameters for the successful application of the method include a metal-free flowpath and a consistent application of anions with sample. Resolution of rhamnose is achieved while maintaining the resolution of xylose and mannose. Simplified sample pretreatment allows a ca. five-fold increase in sample through-put compared with gas chromatography of derivatized sugars or to partition chromatography. Run times are less than half those of the widely used hydroxide reverse gradient method for HPAEC/PAD analysis of wood sugars. Long-term system performance data indicate that the method is highly precise and robust. The acetate loading method affords better precision than those of other HPAEC/PAD methods and of gas chromatographic analysis of alditol acetate derivatives by Tappi Method T249 cm⁻⁸⁵.