**4. Conclusions**

In the present study a new novel material was presented. Particularly, a PU-GO sponge was prepared, taking advantage of the unique properties of GO combined with the characteristics of the common PU sponge. This novel material was applied for the sample preparation of milk samples for the determination of sulfonamides prior to HPLC. The easy preparation of the material and the extremely fast, simple, and green sample preparation procedure make the proposed method suitable for the analysis of a complex matrix such as milk. It is the first time that the PU-GO sponge was applied for the determination of sulfonamides in milk samples. Furthermore, it is a less costly and time-consuming method and requires less equipment than previously reported methods.

**Author Contributions:** Conceptualization, V.F.S. and E.A.D.; methodology, software, validation, formal analysis, investigation, resources, data curation, V.F.S., E.A.D. and M.M. Writing—original draft preparation, V.F.S., E.A.D. and M.M. writing—review and editing, V.F.S. and E.A.D.; supervision, project administration, V.F.S. and E.A.D.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare that there are no conflicts of interest.
