Green solvents in dispersive liquid-liquid microextraction for the determination of carbonyl compounds in coffee extracts

Abstract

This work presents a greener approach for ultrasound-assisted (UA) dispersive liquid-liquid microextraction (DLLME) of carbonyl compounds from coffee samples, before GC–MS determination. This work aims to substitute the solvents used in the traditional DLLME procedures with greener alternatives and to decrease the volume of solvents used. Low-density solvents, 1-octanol and isooctane, were evaluated as the extraction solvent. Optimization of critical experimental parameters was conducted in two stages: an asymmetrical screening design 2331 // 8, followed by a Doehlert experimental design. In the first experimental design 4 parameters were optimized: the volume of aqueous phase volume (1.5 mL), the concentration of the derivatization reagent solution pentafluorophenylhydrazine (1.12 g/L) and the volume and type of extraction solvent (60 µL of isooctane). In the second experimental design, 15 min of derivatization at 50 °C were selected as optimized conditions. The enrichment factor associated with the DLLME procedure enabled the efficient extraction of nine carbonyl compounds (acetaldehyde, acrolein, benzaldehyde, diacetyl, formaldehyde, furfural, glyoxal, malondialdehyde, and methylglyoxal) from coffee samples. The method demonstrated strong analytical performance, with figures of merit including r2 ≥ 0.9990, limits of detection between 289 and 436 µg/L, intraday, and interday precisions < 9.5 %. Recovery values for all nine carbonyl compounds ranged from 90.0 to 110.0 %. The greenness of the developed methodology was assessed using the AGREEprep tool, yielding a score of 0.59. Acetaldehyde, benzaldehyde and furfural were quantified in most coffee samples analyzed, with no significant differences observed in carbonyl compounds composition.