Evaluating the efficacy and specificity of PVPP for phenolic compound removal from natural organic matter

Experimental tests of the enzyme latch hypothesis frequently rely on the removal of phenolic compounds using the phenol binding agent polyvinylpyrrolidone (PVP), yet the extent to which PVP-based approaches alter the composition of the broader dissolved organic matter (DOM) pool remains poorly constrained. Here, we evaluated the selectivity of solid phase polyvinylpolypyrrolidone (PVPP) using Suwannee River Fulvic Acid (SRFA) as a highly characterized representative DOM standard and, for the first time, combined bulk measurements of dissolved organic carbon (DOC) and phenolic removal with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) characterization of residual DOM before and after PVPP treatment. Phenolic binding efficiency increased systematically with PVPP amount and column conditioning, with a rehydrated 1.5 g PVPP-packed column reducing soluble phenolic concentrations by 91%, DOC by 61%, and C-normalized phenolic content from 21% to 5% of the DOM pool. FT-ICR MS analysis revealed that PVPP preferentially removed polyphenolic and condensed aromatic molecular formulae, while leaving the residual DOM enriched in highly unsaturated and aliphatic constituents. These compositional shifts were accompanied by decreases in aromaticity, double-bond equivalents, nominal oxidation state of carbon, and average molecular mass, indicating selective sequestration of aromatic, higher molecular weight DOM. Our results demonstrate that PVPP acts as a strongly selective, but not perfectly specific, adsorbent for phenolic-rich DOM and substantially alters the composition of the remaining DOM pool. This work provides a molecular-level framework for interpreting PVP/PVPP-based phenolic manipulation experiments and establishes best practice guidance for their application in peatland and aquatic biogeochemical research.