New Sample Preparation Method for Honey Volatiles Fingerprinting Based on Dehydration Homogeneous Liquid⁻Liquid Extraction (DHLLE)

Abstract

Qualitative chemical fingerprinting of the honey volatiles by gas chromatography and mass spectrometry (GC-MS) has been an efficient authentication tool that allowed for the classification of the honey botanical origin (strongly related to its medicinal and market value). However, the usage of current sample preparation methods is limited by selectivity of the volatiles extraction from the honey matrix and requires significant solvent volume. Therefore, a new sample preparation method based on dehydrating homogeneous liquid⁻liquid extraction (DHLLE) involving reduced solvent usage was developed for screening volatiles and semi-volatiles from the honey. The effective extraction was achieved by implementing a miscible liquid extraction system (aqueous honey solution/isopropanol) followed by separation through dehydration with MgSO₄ and purification by a solvent polarity change and washing. The method was evaluated by estimating accuracy and precision. The DHLLE method showed satisfactory recoveries (75.2 to 93.5%) for typical honey volatiles: linalool, borneol, terpinen-4-ol, α-terpineol, p-anisaldehyde, eugenol, and vanillin. It also showed superior repeatability with percent relative standard deviation (RSD%) 0.8⁻8.9%. For benzyl alcohol, methyl syringate, and caffeine, the recoveries were 54.3 to 63.9% and 67.3 to 77.7% at lower and higher spiking levels, respectively. Applied to unifloral apple honey, the DHLLE method allowed for the identification of 40 compounds including terpenes, hydrocarbons, phenylpropanoids, and other benzene derivatives, which makes it suitable for fingerprinting and chemical marker screening. The obtained results were comparable or better than those obtained with ultrasonic extraction with dichloromethane.

Keywords: benzene derivatives; green sample preparation method; honey volatiles; terpenes.

Figure 1

Comparison of representative total ion chromatograms of apple honey volatiles extracts obtained using the proposed DHLLE method (a) and the USE extraction with CH₂Cl₂ (b). The numbers correspond to the compounds listed in Table 2.