Organic matter (OM) often co-exists with iron oxyhydroxides in soils to form iron-oxyhydroxide-associated OM. Reducing reagents, such as dithionite and hydroxylamine, have been widely used to selectively extract iron-oxyhydroxide-associated OM from soils for further characterization. However, our results using Fourier transform ion cyclotron resonance mass spectrometry analysis demonstrate that substantial amounts of N- or S-containing molecules, accounting for 20–30% of the total molecules, were present in the OM extracted from soils by hydroxylamine and dithionite. These N- or S-containing molecules contained mainly molecular artifacts formed through reactions between OM and the extractants. Aldehyde-, ketone-, and carbonyl-containing molecules in dissolved organic matter would be expected to react with hydroxylamine and dithionite to form the N- or S-containing molecular artifacts. Both dithionite and hydroxylamine are therefore unsuitable for the extraction of iron oxyhydroxide-associated OM, with the aim of molecular characterization. Moreover, special note should be made of the reactions that occur between OM and chemical extractants to avoid the production of misleading information on OM as a result of the formation of artifacts.

中文翻译：

---

还原剂在提取土壤有机质中诱导分子假象

土壤中的有机物（OM）通常与羟基氧化铁共存，形成与羟基氧化铁相关的OM。还原剂（如连二亚硫酸盐和羟胺）已被广泛用于从土壤中选择性提取与羟基氧化铁相关的OM，以进行进一步表征。但是，我们使用傅里叶变换离子回旋共振质谱分析的结果表明，羟胺和连二亚硫酸钠从土壤中提取的OM中存在大量的N或S分子，占总分子的20％至30％。这些含N或S的分子主要包含通过OM和萃取剂之间的反应形成的分子伪像。醛-，酮-，在溶解的有机物中，含羰基的分子可能会与羟胺和连二亚硫酸盐反应，形成含N或S的分子假象。因此，为了进行分子表征，连二亚硫酸盐和羟胺均不适用于与羟基氧化铁相关的OM的提取。此外，应特别注意OM与化学萃取剂之间发生的反应，以避免由于伪影的形成而产生关于OM的误导性信息。