**5. Conclusions**

The identification of NPS in seized samples still remains a challenge for many laboratories. In cases where a novel unreported substance is found, or when a sample is seized, either in very small amounts or in a complex mixture, routine analytical techniques are often not sufficient. In these cases, an analytical workflow that combines hyphenated techniques with HR-MS, NMR and chemo-informatics tools is the most effective approach to identify and/or confirm the presence of an NPS with sufficient precision.

By following such an analytical workflow, it was possible, in this study, to identify 1B-LSD in the methanol extract of a single blotter paper by using four different techniques and chemo-informatics tools. Although previously characterized at analytical-standard levels, it is the first time that this substance was found and identified in samples circulating in the street market. This work can also be seen as proof that scientific cooperation between modern forensic laboratories can lead to the correct and reliable identification of NPS, even if present in trace amounts.

**Supplementary Materials:** The following are available online, Figure S1: GC chromatogram analysis (Full scan mode) of the blotter paper methanol extract, Figure S2: UHPLC-qTOF-MS analysis of the blotter paper methanol extract (A) and the extracted ion chromatogram (XIC) of the 1B-LSD [M + H]+, Figure S3: 2D COSY NMR spectra of the blotter paper methanol extract; Figure S4: HMBC NMR spectra of the blotter paper methanol extract.

**Author Contributions:** Investigation and experimental analysis, E.T., J.A.L., M.H., F.R., J.Å. and C.G.; Writing—original draft, E.T. and J.A.L.; Revision and experimental follow-ups: E.T., J.A.L., M.H., F.R., J.Å. and C.G.; Visualization and final revision: E.T., J.A.L., M.H., F.R. and C.G. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by EUROPEAN COMMISSION DIRECTORATE GENERAL FOR TAXATION AND CUSTOMS UNIONS (DG TAXUD) for the administrative and financial support provided to the JRC through the Administrative Arrangement CLEN2SAND II (JRC-Nr 34606-DG TAXUD-Nr TAXUD/2016/DE/331).

**Acknowledgments:** Hendrik Emons (JRC) is acknowledged for reviewing this manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.
