Development of a novel non-destructive method based on spectral fingerprint for determination of abused drug in insects: An alternative entomotoxicology approach

Near-infrared spectroscopy (NIRS) is emerging as the tool of choice for non-destructive analysis and the detection of different compounds in biological systems. We evaluate the potential of a novel non-destructive method for the identification of flunitrazepam in Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) larvae, puparia and adult. Necrophagous insects in particular the larvae found in cadavers have been applied as an alternative at the time of death and can also contribute to the qualitative identification of abused drugs present in the corpse. Using this strategy, we have combined a portable NIR spectrometer with variable selection techniques, such as, genetic algorithm-linear discriminant analysis (GA-LDA) and successive projection algorithm (SPA-LDA) for the identification of this drug in the insects based on the unique spectral “fingerprints” of their biochemical composition. Larva, puparium and adult calibrators containing flunitrazepam at concentrations ranging from 0, 4, 8, 16 to 32 pg g− 1 were prepared and analyzed. The resulting GA-LDA model successfully classified adult female with respect to their concentration using only 9 wavenumbers. This alternative approach for entomotoxicology requires further testing, but the obtained results suggest that NIR spectra could be used for abused drug identification in insects.