Department of Chemistry, Institute of Chemistry of Renewable Resources, University of Natural Resources and Life Sciences Vienna (BOKU), Konrad-Lorenz-Strasse 24, 3430 Tulln, Austria.
Department of Bioproducts and Biosystems, Aalto University, 0076 Aalto, Finland.
Carbohydr Polym. 2023 Jun 15;310:120691. doi: 10.1016/j.carbpol.2023.120691. Epub 2023 Feb 18.
Periodate oxidation of cellulose to produce "dialdehyde cellulose" (DAC) has lately received increasing attention in sustainable materials development. Despite the longstanding research interest and numerous reported studies, there is still an enormous variation in the proposed preparation and work-up protocols. This apparently reduces comparability and causes reproducibility problems in DAC research. Two simple but prevalent work-up protocols, namely glycol quenching and filtration/washing, were critically examined and compared, resulting in this cautionary note. Various analytical techniques were applied to quantify residual iodine species and organic contaminations from quenching side reactions. The commonly practiced glycol addition cannot remove all oxidising iodine compounds. Both glycol and the formed formaldehyde are incorporated into DAC's polymeric structure. Quenching of excess periodate with glycol can thus clearly be discouraged. Instead, simple washing protocols are recommended which do not bear the risk of side reactions with organic contaminants. While simple washing was sufficient for mildly oxidised celluloses, higher oxidised samples were more likely to trap residual (per)iodate, as determined by thiosulfate titration. For work-up, simple washing with water is proposed while determining potential iodine contaminations after washing with a simple colorimetric test and, if needed, removal of residual periodate by washing with an aqueous sodium thiosulfate solution.
过碘酸盐氧化纤维素制备“二醛纤维素”（DAC）近来在可持续材料开发领域受到越来越多的关注。尽管人们对此研究已久，已有大量相关报道，但所提出的制备和后处理方案仍存在巨大差异。这显然降低了 DAC 研究的可比性，并导致重现性问题。本文对两种简单但常见的后处理方案（即乙二醇淬灭和过滤/洗涤）进行了批判性检查和比较，并提出了这一警示。采用各种分析技术来定量淬灭副反应产生的残留碘物种和有机污染物。通常采用的乙二醇添加并不能去除所有的氧化碘化合物。乙二醇和形成的甲醛都被结合到 DAC 的聚合物结构中。因此，明显不能鼓励用乙二醇淬灭过量的过碘酸盐。相反，建议采用简单的洗涤方案，因为其不存在与有机污染物发生副反应的风险。虽然简单的洗涤对于轻度氧化的纤维素已经足够，但对于更高氧化的样品，由于过碘酸盐的残留（过），更有可能捕获残留的碘，如通过硫代硫酸钠滴定法确定。对于后处理，建议在洗涤后用简单的比色试验确定潜在的碘污染，并在需要时用含硫代硫酸钠的水溶液洗去残留的过碘酸盐。
