Method Validation and Evaluation of Safrole Persistence in Cowpea Beans Using Headspace Solid-Phase Microextraction and Gas Chromatography.

Maria Suely Siqueira Ferraz,Alessandra Aparecida Zinato Rodrigues,Lucas Henrique Figueiredo Prates,Fernanda Fernandes Heleno,Lêda Rita D’Antonino Faroni,Adalberto Hipólito De Sousa

doi:10.3390/molecules26226914

Abstract

Bioinsecticides are regarded as important alternatives for controlling agricultural pests. However, few studies have determined the persistence of these compounds in stored grains. This study aimed at optimizing and validating a fast and effective method for extraction and quantification of residues of safrole (the main component of Piper hispidinervum essential oil) in cowpea beans. It also sought to assess the persistence of this substance in the grains treated by contact and fumigation. The proposed method used headspace solid-phase microextraction (HS-SPME) and gas chromatography with a flame ionization detector (GC/FID). Factors such as temperature, extraction time and type of fiber were assessed to maximize the performance of the extraction technique. The performance of the method was appraised via the parameters selectivity, linearity, limit of detection (LOD), limit of quantification (LOQ), precision, and accuracy. The LOD and LOQ of safrole were 0.0057 and 0.019 μg kg−1, respectively and the determination coefficient (R2) was >0.99. The relative recovery ranged from 99.26 to 104.85, with a coefficient of variation <15%. The validated method was applied to assess the persistence of safrole residue in grains, where concentrations ranged from 1.095 to 0.052 µg kg−1 (contact) and from 2.16 to 0.12 µg kg −1 (fumigation). The levels measured up from the fifth day represented less than 1% of the initial concentration, proving that safrole have low persistence in cowpea beans, thus being safe for bioinsecticide use. Thus, this work is relevant not only for the extraction method developed, but also for the possible use of a natural insecticide in pest management in stored grains.

Highlights

Cowpea [Vigna unguiculata (L.) Walp.], known as black-eyed pea, belongs to the Fabaceae family and is one of the most cultivated legumes in tropical and subtropical regions, including Asia, Africa, Central and South Americas, the United States, and part of southern Europe [1]
The determination of the chemical composition and relative quantification of the compounds in the P. hispidinervum essential oil (PHEO) were performed via gas chromatography combined with mass spectrometry (GC-MS)
Validation of the Method of Extraction and Analysis The headspace solid-phase microextraction (HS-solid-phase microextraction technique (SPME)) method for safrole determination in cowpea beans was validated, and the results fulfilled the guidelines by SANTE/11813/2017 [49]

Summary

Introduction

Cowpea [Vigna unguiculata (L.) Walp.], known as black-eyed pea, belongs to the Fabaceae family and is one of the most cultivated legumes in tropical and subtropical regions, including Asia, Africa, Central and South Americas, the United States, and part of southern Europe [1]. The continuous and indiscriminate use of these products for treating grains has been questioned worldwide, as they are lethal to non-target organisms [8], lead to resistance development in insect-pest populations [5,9], and potentially pollute the environment [10]. They pose concerns about their residual levels in food and the risks to human health [11]

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