Alginate aerogel beads doped with a polymeric deep eutectic solvent for green solid-phase microextraction of 5-hydroxymethylfurfural in coffee samples

Abstract

A novel sorbent composed of calcium alginate (CA) aerogel beads modified by choline chloride (ChCl):polyethylene glycol (PEG) deep eutectic solvent (DES) in the molar ratio of 1:1 was synthesized through the simple cross-linking and heating methods. The sorbent was characterized by FT-IR and SEM techniques and used in the solid-phase microextraction of 5-hydroxymethylfurfural (HMF) from coffee samples before HPLC analysis. The extraction efficiency of the sorbent was compared with unmodified CA and modified with non-polymeric DES (CA/[ChCl]:[ethylene glycol]) aerogel beads. The significant parameters, including sorbent mass, desorption conditions, sample volume, pH, ionic strength, adsorption time, and desorption time, were studied. The limits of detection and quantification were 2.25 and 7.50 µg kg−1, respectively. The linear range was 7.5–1000 µg kg−1 with a determination coefficient of 0.9962. The precision based on intra-day and inter-day RSDs were 1.1% and 4.1%, respectively. The procedure was applied to the determination of HMF in light, medium, dark roasted coffees, and instant coffee samples, and the extraction recoveries were obtained in 78.5–102.2% (RSDs, 2.5–4.7%). Besides, the effects of the brewing process and sugar addition on HMF concentration in coffee samples were also investigated. Finally, the method greenness was evaluated based on the Complex Green Analytical Procedure Index (Complex GAPI) and the Analytical Eco-Scale (AEC) approaches. This is the first report on the synthesis of novel alginate aerogel beads incorporated with [ChCl]:[PEG] polymeric DES to the best of our knowledge. This paper also represents the first application of green hydrophobic CA/[ChCl]:[PEG] aerogel beads as sorbent for the analysis of HMF in different processed coffee samples.