GC/MS technique and AMDIS software application in identification of hydrophobic compounds of grasshoppers' abdominal secretion (Chorthippus spp.).

The automated mass spectral deconvolution and identification system (AMDIS) is a modern analytical tool, mostly used as a data processing method in environmental studies. The most attractive feature of that software is a fast, automatic data processing, which includes removal of interferences from the overlapping peaks and purification of the obtained mass spectra. The identification of analytes is based on their retention time and retention index and on comparison of the spectra obtained in GC/MS analysis with the spectra from the library of the National Institute of Standards and Technology (NIST). The main aim of the study reported was to elaborate and test a new data processing method with the use of AMDIS software for identification of lipidomic compounds present in the grasshopper's abdominal secretion. For the first time to the best of our knowledge, we have demonstrated the usage of AMDIS in a lipidomic study concerning a complex insect matrix. The samples processed with AMDIS software were analyzed with the use of GC/MS in order to determine the main fatty components of grasshoppers' abdominal secretion. The purification, concentration and fractionation of compounds present in a complex insect matrix were investigated with the use of liquid-liquid extraction as a pretreatment procedure. Moreover, a double-step derivatization process was carried out in order to obtain more volatile and stable derivatives of polar, non-volatile components of insects' secretion. This process, necessary for GC/MS analysis, was performed with the use of methoxyamine hydrochloride dissolved in pyridine and a mixture of bis-N-O-trimethylsilyl trifluoroacetamide (BSTFA) and chlorotrimethylsilane (TMCS). As a result, we obtained a fast, automatic method based on the use of AMDIS software, which enabled identification of 28 analytes, mainly fatty compounds. Moreover, 10 compounds out of 28 were determined to appear with 100% frequency in the tested samples, namely: seven fatty acids, one sterol, one organic acid and one alkaloid. The last part of our study was statistical analysis of average intensities of signals of compounds identified in grasshopper's abdominal secretion in order to differentiate insects collected at two distant locations in Poland: Starogard Gdański and Łubianka meadows.