Validation of a modified Flory‐Huggins concept for description of hydrophobic organic compound sorption on dissolved humic substances

Abstract

Sorption coefficients (K(DOC)) on dissolved organic matter (DOM) have been determined by means of solid-phase microextraction (SPME) for hydrophobic organic compounds (HOCs) of various classes, for example, polycyclic aromatic hydrocarbons (PAHs), noncondensed arenes, and alkanes. Relating the K(DOC) values obtained to the octanol-water partition coefficients of the solutes results in class-specific correlations. Obviously, PAHs have a higher affinity to DOM than other HOCs with equal K(OW) values. The different K(DOC) to K(OW) correlations can be combined into one general formula based on a modified Flory-Huggins concept. It permits the calculation of sorption coefficients from the solubility parameters (delta) and K(OW) values of the solutes and the solubility parameter of the sorbent. The latter value, which is specific to the DOM under consideration, can be determined from a single measured sorption coefficient. By applying the proposed Flory-Huggins concept, which is based on the presumption of nonspecific interactions between HOCs and DOM, the different affinities of PAHs, noncondensed arenes, and alkanes to DOM can be accurately predicted.