## 4 Conclusions  
The HS-SPME-GC/FID method was optimized for extracting safrole from PHEO-treated cowpea beans. The optimal conditions were 60 \({}^{\circ}\)C and 10 min extraction time, using a 50/30-\(\upmu\)m DVB/CAR/PDMS StableFlex fiber. The optimized method showed good linearity (within the tested range), repeatability, and suitable LOD and LOQ. During the storage of cowpea beans treated with PHEO by contact, safrole concentrations varied from 1.095 to 0.052 ug kg\({}^{-1}\). When the compound was applied by fumigation, the levels ranged between 2.16 and 0.12 ug kg\({}^{-1}\).  
Figure 5: Persistence of safrole residue in cowpea beans treated with _Piper hispidinervum_ essential oil, either by contact (**A**) or fumigation (**B**), throughout storage. Sample mass: 5.0 g; extraction: 60 \({}^{\circ}\)C for 10 min (\(n=3\)).  
PHEO had low persistence in cowpea beans treated by either fumigation or contact. The safrole residue detected after 5 days of storage represented less than 1% of the initial concentration.  
Based on our current results and the insecticidal potential already reported in the literature, it is possible to conclude that PHEO shows potential to preserve the quality of stored cowpea beans by inhibiting the development of this insect-pest species. Moreover, safrole has low persistence in the grains, suggesting that PHEO is a safe option that might be also suitable for treating similar food products. Additionally, the optimized HS-SPME-CG/FID method can be successfully used to determine the presence of safrole in cowpea beans.  
Conceptualization, L.R.D.F., F.F.H., A.H.d.S. and A.A.Z.R.; data curation, M.S.S.F.; formal analysis, A.H.d.S., L.H.F.P. and A.A.Z.R.; investigation, F.F.H. and L.H.F.P.; methodology, M.S.S.F. and L.H.F.P.; resources, L.R.D.F.; supervision, L.R.D.F. and A.H.d.S.; validation, M.S.S.F. and L.H.F.P.; writing--original draft, M.S.S.F. and F.F.H.; writing--review and editing, L.R.D.F. and A.A.Z.R. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Fundacao de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG), Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), and Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior--Brazil (CAPES)--Finance Code 001. The APC was funded by \"Graduate Program in Agricultural Engineering\" of Universidade Federal de Vicosa (UFV)--PPGEA-UFV.  
Not applicable.  
The authors are grateful to the Department of Chemistry and Department of Agricultural Engineering of the Federal University of Vicosa (Brazil) for support and research facilities. The authors also thank the Federal University of Ace for providing the essential oil of Piper hispidinervum for the research. The authors would like to thank the Brazilian Agencies: Fundacao de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG), Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq). Also, this study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior-Brazil (CAPES)-Finance Code 001.  
The authors declare that they have no conflict of interest.  
Samples of the compounds are not available from the authors.