Green method for quantification of lavender and sweet orange essential oils in blends by synchronous fluorescence first derivative

A simple green method for the quantification of sweet orange and lavender essential oils (EOs) content in blends was developed using synchronous fluorescence of the first derivative spectra and sample preparation by surfactant-free microemulsions (SFMEs). Excitation and emission wavelengths pairs (λex/λem) were determined for both EOs (at 336/436 nm for sweet orange and at 330/388 nm for lavender). Optimization was conducted to establish the condition to prepare the SFMEs systems: 50 μL of oily phase containing EO diluted in octan-1-ol (1:4, v/v), 2.0 mL of water and propan-1-ol up to 5.0 mL final volume. Different proportions of EO in the oily phase were evaluated for analytical curves construction. Synchronous fluorescence measurements were performed and the acquired data were corrected by inner filter effect. Considering the first derivative of the synchronous scanning, data were extracted at 316.8 nm (Δλ = 100 nm) and 352.0 nm (Δλ = 58 nm) for sweet orange and lavender EOs, respectively, with correlation coefficients above 0.99. Limits of quantification of 7.97 μg mL−1 and 65.80 μg mL−1 were obtained indicating that 0.46% of sweet orange and 3.69% of lavender EOs can be quantified in mixtures. Simulated blends (25:75%, 50:50% and 75:25%, volume proportions) were also evaluated with recoveries of 71.5 – 128.9% and coefficient of variation between 3.1% – 11.6%. Additionally, the method's greenness was evaluated through three green metrics (Analytical Eco-Scale, GAPI, and AGREE) with consistent results.