Determination of in-chain ketone functionality distribution in polyolefin materials via a selective 2,4-dinitrophenylhydrazine (DNPH) derivatization.

Selective determination of in-chain ketone functionality distribution in polyolefin materials remains analytically challenging due to limited solubility and interference from other carbonyl-containing groups. Here a mild and selective 2,4-dinitrophenylhydrazine (DNPH) derivatization approach that enables efficient labeling and quantitative analysis of in-chain ketone groups in ethylene-n‑butyl acrylate-ketone (EnBACO) terpolymers is reported. A tetrahydrofuran/formic acid (THF/FA) reaction medium dissolves the polyolefin matrix while preserving ester functionalities, allowing high derivatization efficiency without detectable side reactions. Conversion exceeding 90% was confirmed by FTIR and NMR spectroscopy. The DNPH-labeled polymers were analyzed by gel permeation chromatography with dual ultraviolet and refractive index detection (GPC-UV/RI). The UV/RI signal ratio provides a sensitive metric for monitoring derivatization kinetics and evaluating ketone functionality distribution across the molecular weight distribution. Similar UV and RI chromatographic profiles indicate a uniform distribution of in-chain ketone functionalities.