Detection of Tribolium castaneum (Herbst) volatile defensive secretions by solid phase microextraction–capillary gas chromatography (SPME-CGC)

Abstract

The solid phase microextraction (SPME) technique was used for the collection of the volatile defensive secretions released by Tribolium castaneum (Herbst), the red flour beetle. The detection of the major components methyl-1,4-benzoquinone (MBQ) and ethyl-1,4-benzoquinone (EBQ), together with 1-pentadecene (C15:1), was performed by capillary gas chromatography (CGC). SPME samples were identified by CGC coupled to mass spectrometry (MS). Volatile organic compounds (VOC) released from insects were compared employing different SPME fibers. The relative amounts of the major volatiles collected varied with the fiber coating. Quinones accounted for ∼75% of the volatiles trapped by the carboxen/polydimethylsiloxane (CAR/PDMS) fiber, whereas they only represented ∼45% of the volatiles trapped with the PDMS fiber. The PDMS/divinylbenzene (DVB) coating exhibited intermediate affinity. In a 15-min extraction period, the highest amounts of VOC extracted from disturbed insects with CAR/PDMS were 349±107 ng/beetle of MBQ, 780±290 ng/beetle of EBQ, and 144±69 ng/beetle of C15:1. The total VOC amounts extracted by SPME were estimated by adding the disturb-released VOC to heat-released VOC of the same insects, resulting in 742±93 ng/beetle of MBQ, 1672±244 ng/beetle of EBQ, and 946±237 ng/beetle of C15:1. SPME-CGC is a simple method to detect and estimate T. castaneum volatiles. This method has the potential to detect insect infestation in stored products.