Determination of molecular weight parameters of native and, in particular, technical lignins are based on size exclusion chromatography (SEC) approaches. However, no matter which approach is used, either conventional SEC with a refractive index detector and calibration with standards or multi‐angle light scattering (MALS) detection at 488 nm, 633 nm, 658 nm, or 690 nm, all variants can be severely erroneous. The lack of calibration standards with high structural similarity to lignin impairs the quality of the molar masses determined by conventional SEC, and the typical fluorescence of (technical) lignins renders the corresponding MALS data rather questionable. Application of MALS detection at 785 nm by using an infrared laser largely overcomes those problems and allows for a reliable and reproducible determination of the molar mass distributions of all types of lignins, which has been demonstrated in this study for various and structurally different analytes, such as kraft lignins, milled‐wood lignin, lignosulfonates, and biorefinery lignins. The topics of calibration, lignin fluorescence, and lignin UV absorption in connection with MALS detection are critically discussed in detail, and a reliable protocol is presented. Correction factors based on MALS measurements have been determined for commercially available calibration standards, such as pullulan and polystyrene sulfonate, so that now more reliable mass data can be obtained also if no MALS system is available and these conventional calibration standards have to be resorted to.

中文翻译：

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接近工业木质素的绝对摩尔质量

天然木质素、特别是工业木质素的分子量参数的测定基于尺寸排阻色谱 (SEC) 方法。然而，无论使用哪种方法，无论是带有折射率检测器和标准校准的传统 SEC，还是在 488 nm、633 nm、658 nm 或 690 nm 处进行多角度光散射 (MALS) 检测，所有变体都可能会严重影响检测结果。错误。缺乏与木质素具有高度结构相似性的校准标准品会损害传统 SEC 测定的摩尔质量的质量，并且（技术）木质素的典型荧光使相应的 MALS 数据相当可疑。使用红外激光在 785 nm 处应用 MALS 检测在很大程度上克服了这些问题，并可以可靠且可重复地测定所有类型木质素的摩尔质量分布，这一点已在本研究中针对各种结构不同的分析物得到证明，例如如硫酸盐木质素、磨碎木质素、木质素磺酸盐和生物精炼木质素。详细讨论了与 MALS 检测相关的校准、木质素荧光和木质素紫外吸收等主题，并提出了可靠的方案。基于 MALS 测量的校正因子已针对市售校准标准（例如普鲁兰多糖和聚苯乙烯磺酸盐）确定，因此，如果没有可用的 MALS 系统并且必须求助于这些传统校准标准，现在也可以获得更可靠的质量数据。