ATR-FTIR spectroscopy and GC-MS data of blow fly puparia

This study uses empty puparia of four forensically relevant blow fly species. Species identification of these insect traces at scenes of discoveries of human remains, is neccessary to help with the estimation of the minimal time since death. Since morphological species identification of (fragmented) puparia is difficult, new methods for species identification, like ATR-FTIR spectroscopy and GC-MS are tested.

Empty puparia of Lucilia sericata, Calliphora vicina, Protophormia terraenovae and Chrysomya albiceps were stored in garden soil at 25 °C for either one day or one month. Puparia were cleaned, cut into fragments and measured on an ATR-FTIR spectrometer (JASCO FT/IR-4200 with PIKE Technologies GladiATR accessory) or were subjected idividually to n-hexane and the extract was measured on a 7890A, Agilent Technologies gas chromatograph. While ATR-FTIR spectral data was normalized via the standard normal variate, the chromatograms resulting from GC-MS were analyszed using MSD ChemStation and the integration and peak alignment was done manually. Non-hydrocarbons, hydrocarbons with an overall maximum abundance below 0.5% and hydrocarbons that occurred in less than 20% of the samples of either species or treatment were removed from the dataset.

tecRep = technical replicate (i.e. single puparia), bioRep = biological replicate (i.e. separate oviposition events of the blow flies), Age = storage/weathering time of the puparia -> 1D = 1 day 1M = 1 Month, CA = Chrysomya albiceps, CV = Calliphora vicina, LS = Lucilia sericata, PT = Protophormia regina, RI = retention index.
In the column “hydrocarbon”, “unknown CHC” = substances identified as hydrocarbons. “unknown” = substances where we could not unambigously decide whether or not it was a hydrocarbon, and/or where the peak represented a blend of a hydrocarbon and a non-hydrocarbon compound, “unknown, unsaturated” = unknown hydrocarbon, but the mass spectrum indicates at least one unsaturation, (cf) = identification tentative.