Headspace Solid-Phase Microextraction: Validation of the Method and Determination of Allyl Isothiocyanate Persistence in Cowpea Beans.

Essential oils are widely recognized as an efficient and safe alternative for controlling pests in foods. However, a few studies have determined the persistence of these compounds in stored grains. The present study optimized and validated a fast and effective method for extraction and quantification of allyl isothiocyanate (AITC-the main component of mustard essential oil) residue in cowpea beans. It also investigated the persistence of this substance in the grains. The proposed method employs headspace solid-phase microextraction (HS-SPME) and gas chromatography with a flame ionization detector (GC/FID). For optimizing it, a central composite design (CCD) was used, where the best conditions for the extraction of the AITC were achieved using 15 min fiber exposure at 30 °C. The performance of the method was assessed by studying selectivity, linearity, limits of detection (LOD) and quantification (LOQ), precision, and accuracy. The LOD and LOQ for AITC were 0.11 and 0.33 μg kg, respectively. The determination coefficient ( ) was above 0.99. The relative recovery rate ranged from 108.2 to 114.8%, with an interday coefficient of variation below 9%. After 36 h, no residue was detected in the samples, demonstrating that the AITC has low persistence and can be safely used as a bioinsecticide for grains.