Polyamine-Modified Magnetic Graphene Oxide Nanocomposites and HPLC-MS/MS Allow the Determination of Two Indolic Derivatives in Strong-Aroma Types of Base Baijiu

Simultaneous detection of 3-indoleacetic acid (IAA) and 3-indolepropionic acid (IPA) in strong-aroma types of base Baijiu (base SAB) is crucial for elucidating the metabolic pathway of 3-methylindole during the base SAB brewing. Herein, a novel magnetic poly­(allylamine)-modified graphene oxide (GO@PAA@Fe3O4) was synthesized as extraction sorbent, followed by high performance liquid chromatography mass spectrometry HPLC-MS/MS. As a surface modifier of GO, the introduction of PAA and Fe3O4 provided more adsorption sites for IAA and IPA, mainly through the generation of H-bonding sites. Moreover, modified by an activation step, the capacity of the activated GO@PAA@Fe3O4 for the adsorption of IAA and IPA was 2.1–3.4 times higher than that of unactivated material. The adsorptions of IAA and IPA on GO@PAA@Fe3O4 were fitted to the pseudo-second-order kinetic model and Langmuir isotherm, respectively. Under the optimal conditions, IAA and IPA were determined in 16-base SAB for the first time, and their concentrations ranged from 0.6 to 11.3 and 0.7 to 18.7 μg/L, respectively.