Technical Abstract: Xylan is a barrier to enzymatic hydrolysis of plant cell walls. It is well accepted that the xylan layer needs to be removed to efficiently hydrolyze cellulose and consequently pretreatment conditions are in part optimized for maximal xylan depolymerization or displacement. Xylan consists of a long chain of beta 1,4-linked xylose units substituted with arabinose (usually alpha-1,3-linked in grasses) and glucuronic acid (alpha-1,2-linked). Arabinose units can be further substituted with acids (acetic, uronic, and phenolic acids) and/or hexose. It has been proposed that the substitutions are not random along the xylan chains but rather occur as domain structures suggesting they have a structural function and therefore may play a role in determining reactivity of xylan to pretreatment. Analysis of intact xylan is problematic because of its chain length and heterogeneous side groups; therefore, we explored conditions to partially hydrolyze alkaline-extracted switchgrass xylan, with and without prior modification, for analysis of the resultant multimeric fragments by high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) to determine conditions producing a distribution of information-rich arabinoxylooligomers. A two-step process of oxidation followed by acid depolymerization provided oligosaccharides containing the desired arabinose branches intact. Selected samples were derivatized with a reducing end label and analyzed by hydrophilic interaction chromatography-liquid chromatography-mass spectrometry/mass spectrometry (HILIC-LC-MS/MS) to demonstrate the potential utility of this chemistry for determining the sequence of arabinoxylooligosaccharides present in plant cell wall material.