Diane M. McKnight K. A. Thorn E.M. Thurman G. R. Aiken 1992 <div id="abstracts" class="Abstracts u-font-serif"><div id="aep-abstract-id5" class="abstract author"><div id="aep-abstract-sec-id6"><p>A method has been developed for the isolation of hydrophilic organic acids from aquatic environments using Amberlite<a class="workspace-trigger" name="bFN1" href="https://www.sciencedirect.com/science/article/pii/014663809290119I?via%3Dihub#FN1" data-mce-href="https://www.sciencedirect.com/science/article/pii/014663809290119I?via%3Dihub#FN1">^∗</a><span>&nbsp;</span>XAD-4 resin. The method uses a two column array of XAD-8 and XAD-4 resins in series. The hydrophobic organic acids, composed primarily of aquatic fulvic acid, are removed from the sample on XAD-8, followed by the isolation of the more hydrophilic organic acids on XAD-4. For samples from a number of diverse environments, more of the dissolved organic carbon was isolated on the XAD-8 resin (23–58%) than on the XAD-4 resin (7–25%). For these samples, the hydrophilic acids have lower carbon and hydrogen contents, higher oxygen and nitrogen contents, and are lower in molecular weight than the corresponding fulvic acids.<span>&nbsp;</span>¹³C NMR analyses indicate that the hydrophilic acids have a lower concentration of aromatic carbon and greater heteroaliphatic, ketone and carboxyl content than the fulvic acid.</p></div></div></div> application/pdf 10.1016/0146-6380(92)90119-I en Elsevier Isolation of hydrophilic organic acids from water using nonionic macroporous resins article