基于亲水性可控棉线有效分离苏丹I和罗丹明B

近年来,食品安全问题引起了人们的广泛关注.非食用色素因价格低廉、着色能力强而被非法用于食品加工过程,严重威胁消费者生命健康.苏丹I和罗丹明B是食品加工中最常被滥用的两种典型非食用有机着色剂,进入人体后会在相应酶的作用下产生致癌物.高效液相色谱法是用于违禁色素分离检测的主要方法,但该方法所需仪器昂贵,专业程度高且操作繁琐,限制了其在色素鉴定中的应用.棉线作为一种低成本固定相已被用于有机色素的色谱分离,但是对于其亲疏水性在色素分离中的作用目前仍不清楚,也未见将该系统直接用于色素分离收集的报道.针对上述问题,本研究采用等离子体可控预处理的方式实现对棉线亲疏水性能的调控,并进一步探究了棉线亲疏水性在棉线基色谱分离和收集过程中的作用.在等离子体处理过程中,调整了棉线的缠绕方式、等离子体功率和暴露时间,并通过扫描电镜、接触角测试和线上液体流动实验对棉线内部结构以及棉线亲疏水性进行了表征.结果表明,等离子体处理并不影响棉线的加捻结构和纤维间空隙大小;棉线以"之"字形悬空缠绕在支架上可增大暴露面积,从而获得更高的亲水性能;棉线的亲水性高度依赖于等离子处理时间和仪器功率,在10.15 W的等离子机中处理8 min被证明是最佳处理参数,可使棉线具有最高的亲水性能.X射线光电子能谱分析(XPS)表明,经等离子体处理后棉线的含氧基团显著增多,这可能是棉线亲水性提高的原因.以乙醇/水溶液为展开剂,探究了棉线亲水性对色素分离的影响,发现棉线亲水性提高可以显著增强色素的分离效果.色素与棉线的结合力以及流动相在棉线上的流动能力可能是色素分离效果的决定性因素.在色素分离收集实验中,分别以乙醇/水溶液和甲酸/甲醇溶液作为展开剂对罗丹明B和苏丹I进行分离收集,并对不同阶段的洗脱液进行了紫外吸收光谱分析.在乙醇/水溶液体系中,两种色素虽然可先后通过棉线固定相,但在苏丹I洗脱液中仍然含有微量的罗丹明B;而在甲酸/甲醇溶液体系中,两种色素可以更有效地分离,且分离速度更快.综上,本研究揭示了亲水性在线基色谱系统中的关键作用,开发了一种简便、低廉和易于操作的线基色素分离方法,并将其用于非食用色素苏丹I和罗丹明B的有效分离和收集.本研究有望为高性能线基色谱分离系统的设计和构建提供理论指导,并进一步拓展线基流控分离方法的应用领域.

Tailoring Hydrophilicity of Cotton Thread for Efficient Separation of Sudan I and Rhodamine B

Thread has been used as a low-cost solid phase for chromatographic separation of organic pigments. However, the role of thread hydrophilici-ty in the separation has not been systematically investigated. Moreover, direct harvesting of separated pigments has not been achieved, ei-ther. Herein, a cotton thread-based system with controlled hydrophilicity was fabricated for the separation and harvesting of Sudan I and Rhoda-mine B in the mixture. The thread was exposed to oxygen plasma at different powers, durations and enwinding ways to tailor its hydrophilicity. The thread enwound on a shelf in a zigzag pattern could reach the highest hydrophilicity after exposure to the plasma at the power of 10.15 W for 8 min. The separation of Sudan I and Rhodamine B greatly depends on the thread hydrophilicity and the solvent used to dissolve them. The pig-ments-formic acid/methanol system could achieve the most effective separation on the thread with the highest hydrophilicity. A mechanism invol-ving the affinity of pigments to the fibers and the transfer capability of the solvent was proposed to explain the hydrophilicity-dependent separation process on the thread. Based on the mechanism, the separated pigments were eluted from the thread-based chromatographic system with formic acid/methanol solution. Rhodamine B can be harvested at the initial 20 min. After 30 min, Sudan I is the prominent substance in the eluted solu-tion. This work may not only reveal the critical role of hydrophilicity in the thread-based chromatographic system, but also expand its application in pigment separation and harvest.