Fan assisted extraction and low pressure chromatographic system with a phenyl monolithic column for amperometric determination of volatile α-dicarbonyl compounds in coffee brews

Abstract

In this work, a low pressure chromatographic system featuring a single 0.5 cm length phenyl monolithic column and an amperometric detector was developed to determine volatile ⍺-dicarbonyl compounds in coffee brews. The analytical strategy relied on the extraction of the volatile ⍺-dicarbonyl compounds and their derivatization with o-phenylenediamine, prior to the determination of the resulting quinoxaline derivative compounds in the designed chromatographic system. The studies of the mobile phase composition and electrochemical conditions are presented. The extraction of the volatile ⍺-dicarbonyl compounds was performed resourcing to a recent approach based on the fan assisted extraction system. This system performs the full evaporation technique and allowed the quantitative recovery (>85 %) of diacetyl and 2,3-pentanedione from the coffee brew based on the following experimental conditions: sample volume 30 µL, extraction period 15 min, acceptor solution (water, acetonitrile, 90:10, v/v) volume 400 µL, and sample temperature 50 °C. The developed method showed no matrix effect for different coffee brews and the quantification of the studied analytes can be performed through the external calibration method. Detection limits of 3.6 × 10⁻⁶ mol/L for diacetyl and 12.9 × 10⁻⁶ mol/L for 2,3-pentanedione were obtained. Sample analysis rate was of 5 h⁻¹ and the acetonitrile consumption was of ca. 450 µL per chromatographic run.