High-throughput analysis of target furocoumarins in Citrus essential oils by supercritical fluid chromatography with bio-based solvents

In recent years, the demand for greener analytical workflows has led to a renewed interest in supercritical fluid chromatography (SFC), which uses recycled carbon dioxide as the main mobile phase. In addition, the low viscosity of the supercritical CO2 enables faster separations with a minimal consumption of organic solvents. A fast and high-throughput SFC method was developed in this work, for the screening of target oxygenated heterocyclic compounds (OHCs) in Citrus essential oils. These matrices are widely used in the formulation of fragrances and topical cosmetic products, and thus accurate and reliable methods are imperative for industries, given the phototoxic potential of some OHCs. A systematic investigation of stationary phases and co-solvents was carried out to assess the retention behaviour of the analytes as a function of key operational parameters (mobile phase modifier, flow rate, temperature, and pressure). Compared to conventional liquid-chromatography workflows, the SFC method resulted in a substantial decrease in analysis time (3.5 min per sample) and solvent usage (840 µL per run). Moreover, toxic solvents and additives were replaced with lower amounts of bio-based chemicals (6% of bio-methanol into CO2, isocratically). High-throughput capability (17 samples per hour) and minimal environmental impact render the method consistent with the overarching aims of green analytical chemistry, and suitable for sustainable routine quality control of essential oils. Quantitative analysis of target OHCs in bergamot, bitter orange, lemon, and grapefruit cold-pressed oils was performed, afterwards. The limits of detection and quantification were estimated in the 0.016–0.048 and 0.053–0.162 mg L-1 range, respectively.