## 4 Conclusions  
Characterization of complex plant extracts is commonly time-consuming due to the need for various analytical approaches for structurally different compounds. Here, the HILIC method was developed for willow bark extract, which is known to be rich in aromatic compounds, especially picein and triandrin, as well as the monosaccharides fructose and glucose. These compounds are commonly quantified using gas chromatography after a laborious derivatization procedure. HILIC coupled with ELSD and UV detectors proved to be a fast separation and quantification method for both aromatic compounds and monosaccharides. Ternary eluent consisting of ACN, water, and methanol (80/14/6) resulted in baseline separation between picein and triandrin, and short retention times for fructose and glucose. This minimized the time needed for the analysis. ELSD allowed for the quantification of aromatic compounds and monosaccharides at a level of 10-125 ppm. HILIC can be considered a promising separation technique for plant extract screening containing both polar carbohydrates and semi-polar aromatic compounds. The following are available online at [[https://www.mdpi.com/article/10](https://www.mdpi.com/article/10)]([https://www.mdpi.com/article/10](https://www.mdpi.com/article/10)) 3390/app11093808/s1, Figure S1: Calibration curves for glucose and picein obtained by HILIC-ELSD. Table S1: The amounts of picein, triandrin, (+)-catechin, fructose, and glucose in willow bark extract presented as mg/g. Conceptualization, H.M.-T., L.P., J.D. and T.V. ; methodology, H.M.-T. and L.P.; validation, H.M.-T. and L.P.; formal analysis, H.M.-T. and L.P.; investigation, H.M.-T., L.P. and J.D. ; writing--original draft preparation, L.P.; writing--review and editing, H.M.-T., J.D. and T.V. All authors have read and agreed to the published version of the manuscript. No specific funding for this paper. Not applicable. The authors thank [PERSON] and [PERSON] from University of Wisconsin-Madison for the triandrin sample. We thank [PERSON] from LUT University for information regarding the limits of quantification for monosaccharides using the chromatographic system with RI detection. The authors thank [PERSON] from Aalto University and [PERSON] from Abo Akademi for assistance with the HPAEC-PAD and GC-FID techniques. This work was part of the Academy of Finland's Flagship Programme under Projects No. 318890 and 318891 (Competence Center for Materials Bioeconomy, FinnCERES). This work made use of Aalto University's Bioeconomy Facilities. The authors declare no conflict of interest. References  
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