Humic substances are organic mixtures of extreme complexity, which significantly complicate their analysis by any method. Fractionation into more homogeneous mixtures seems to be almost the only way to overcome these difficulties. Preparative high-performance liquid chromatography (HPLC) provides almost any amounts of substances required for both further fractionation and studies by other methods. For the first time, isopropyl alcohol (IPA) is proposed for these purposes; its advantages are shown by the example of groundwater fulvic acids (FA). IPA is much safer than conventional solvents and elutes the most nonpolar compounds that are nonelutable by methanol and acetonitrile. The isolated fractions differ significantly in their molecular composition, which is confirmed by ultrahigh-resolution mass spectrometry and molecular spectroscopy. Stepwise IPA-gradient HPLC-UV analysis of each preparative fraction demonstrates the possibilities of multidimensional HPLC for FA. The isolated fractions were studied for contents of a broad range of elements, and the relationships between the molecular and trace-element compositions of the fractions were revealed. Our data reveals the existence of numerous and different organometal compounds in FA composition; thus, the proposed approach can be used for a more in-depth study of the mechanisms of element migration in the environment.

中文翻译：

---

通过制备型反相高效液相色谱和多维 RP-HPLC 释放异丙醇作为环保型洗脱液在黄腐酸大规模分馏中的潜力：分子多样性和元素组成的评估


腐殖质是极其复杂的有机混合物，这使得任何方法的分析都非常复杂。分馏成更均匀的混合物似乎几乎是克服这些困难的唯一方法。制备型高效液相色谱 （HPLC） 可提供进一步分离和通过其他方法进行研究所需的几乎任何量的物质。异丙醇 （IPA） 首次被提议用于这些目的;地下水黄腐酸 （FA） 的例子说明了它的优势。IPA 比传统溶剂安全得多，并且可以洗脱大多数非极性化合物，这些化合物不能用甲醇和乙腈洗脱。分离的馏分的分子组成存在显着差异，这可以通过超高分辨率质谱和分子光谱得到证实。每个制备馏分的逐步 IPA 梯度 HPLC-UV 分析证明了多维 HPLC 用于 FA 的可能性。研究了分离馏分中多种元素的含量，并揭示了馏分的分子和微量元素组成之间的关系。我们的数据揭示了 FA 成分中存在大量不同的有机金属化合物;因此，所提出的方法可用于更深入地研究环境中元素迁移的机制。