Fast HILIC Method for Separation and Quantification of Non-Volatile Aromatic Compounds and Monosaccharides from Willow (_Salix_ sp.) Bark Extract  
[PERSON]  
Department of Bioproducts and Biosystems, Aalto University, P.O. Box 16300, 00076 Espoo, Finland; [EMAIL_ADDRESS] (H.M.-T.); [EMAIL_ADDRESS] (J.D.); tapani.  
Plant water extracts contain a mixture of chemically heterogeneous compounds. Thus, characterizing these compounds from a mixture is a challenging task. The water extract of willow bark from the hybrid Karin is reported to be rich in aromatic compounds and monosaccharides. These include picein, (+)-catechin, triandrin, glucose, and fructose. Gas chromatographic methods (gas chromatography coupled to mass spectrometry (GC-MS) and gas chromatography coupled to flame ionization detector (GC-FID)) were used for separation, identification, and quantification of these compounds after trimethylsilylation [2]. In addition to gas chromatographic characterization methods, HPLC has also been used for the characterization of phenolic compounds from willow bark water extract [3; 8]. In these studies, reversed-phase columns have been used for the separation of phenolic compounds from willow bark extract, together with MS detection for compound identification. Low-molar-mass carbohydrates can also be separated and quantified with GC-FID, or alternatively using ion chromatography [9]. High-performance anion-exchange chromatography coupled with pulse-amperometric detection (HPAEC-PAD), a variant of ion chromatography, is nowadays the gold standard method for characterization of mono- and oligosaccharidesudies due to the high sensitivity of PAD detection for carbohydrates [10; 11]. Ion exclusion chromatography and hydrophilic interaction liquid chromatography (HILIC) separations with refractive index (RI) detection and evaporative light scattering detection (ELSD) have also been used for the characterization of mono- and oligosaccharidesudies [12; 13]. The HILIC technique seems promising for simultaneous separation of both polar carbohydrates and semi-polar aromatic compounds. The exact separation mechanism of HILIC has not been established, but it combines the characteristics of normal-phase, reversed-phase, and ion chromatography. The stationary phase in HILIC columns are polar and it is assumed that water, which is used in the eluent (commonly \(\geq\)3% in eluent), forms a thin layer on the surface of the stationary phase. Retention is facilitated by the distribution of analytes between the water layer and organic solvent in eluent (commonly \(\geq\)80% in eluent). Ionic interactions may also contribute to the retention [14].  
In this study, the HILIC method was developed for fast and simultaneous separation of both phenolic compounds, as well as monosaccharides, from willow bark extract. In the HILIC method, filtration of the sample is the only sample preparation step, which makes this method more convenient than GC, in which derivatization is needed prior to analysis. The HILIC method can be used for the screening of plant extracts containing both phenolic compounds and monosaccharides, as well as investigating the purity of the isolated bioactive compounds.