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Hardwoods contain a substantial amount of hemicellulose-type oligosaccharides, the chemical structures of which are typically categorized in the xylan saccharide class. The efficient and selective isolation of these hemicelluloses is regarded as one of the most critical obstacles to overcome for their eventual biomaterial and bioenergy utilization. Therefore, the objective of the current work was to perform a fundamental exploration of the function of extraction pH, temperature, and time on the final chemical properties of the extracted hemicelluloses. The extraction chemistries employed varied pH and showed that acidic conditions provided a higher extractive yield versus alkaline conditions. An alkaline environment gave higher yields than an acidic environment and also resulted in much higher lignin removal from wood, especially at high temperature. In general, control of the pH chemistry leads to a change in the carboxylic acid groups present in the extracts. When the extraction pH changed from acidic to alkaline, the total carboxylic acid group content in the hemicelluloses removed significantly increased due to more acetic acid group hydrolysis and increased lignin degradation.

Spectra of highly acidic oligosaccharides obtained by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) can be greatly enhanced in quality by coating the MALDI probe surface with a film consisting of a perfluorosulfonated ionomer (Nafion) prior to the addition of the sample-matrix mixture. For comparison, three mixtures containing highly acidic oligo- and polysaccharides derived from partial acidic hydrolysis of alginate, pectin, or carboxymethyl cellulose (CMC) were analyzed by employing probes with an uncoated gold surface or a surface coated with a Nafion or nitrocellulose film. The negative ion-mode MALDI spectra of the oligouronates (oligomers containing mannuronic/guluronic and galacturonic acid residues) obtained using uncoated or nitrocellulose-coated probes consisted of a series of broad, multiple peaks. These multiple peaks were assigned to the molecular ions of the nondissociated [M - H]- and partially sodiated [MnNa - H]-, where n = 1, 2, or 3, oligomers. In contrast, the corresponding spectra obtained with Nafion-coated probes contained only a single series of sharp peaks originating from the molecular ions ([M - H]-) of nondissociated oligomers exhibiting chain lengths of as many as approximately 15 uronic acid residues. The Nafion coating was apparently capable of removing the sodium counterions remaining in the deposit of the sample-matrix mixture on the probe, thereby greatly enhancing the signal-to-noise ratios of the peaks in the spectra. In a similar manner, higher quality spectra could also be obtained by using Nafion-coated probes for analysis of the oligouronates and CMC oligomers by positive ion-mode MALDI-MS.