Determination Of Trace Level Of Octopamine In Blattela Germanica L. By Derivative Capillary Gas Chromatography And Electron Capture Detection

Octopamine (OA) constitutes one of biogenic amines in the invertebrate nervous system. It has been suggested that distribution and level of OA has greatly significant effect on insect physiological processes including growth, feeding and reproduction. In this study capillary gas chromatography with electron capture detector (GC-ECD) and capillary gas chromatography coupled with mass detector (GC-MS) were developed to determine the content of OA in Blattela germanica L. central nervous system, and that of OA in cockroach stressed by representative insecticides, known octopaminergic agonists or some essential oils. Capillary GC-MS was performed to identify the structure of the derivative products with pentafluoropropionic anhydride (PFPA), and a method was established to quantify the amount of OA in insect issues by capillary GC-ECD through an extraction-derivation-liquid/liquid partition procedure. Thus, the optimized conditions include: extracting the insect homogenates with pH 7.2 phosphate buffer and then extracting twice with ethyl acetate in the presence of anhydrous sodium sulphate and ammonia by vortexing for 1 min. After centrifuging, the organic layer was evaporated under dride nitrogen gas, then 1 mL solvent, 1 mL phosphate buffer and 40 mu L PFPA was added to the solution, which was incubated at 60'C for 20 min in a water bath. After derivative reaction, the resulting residue was reconstituted with hexane-ethyl acetate (4: 1) to 5 mL and was injected into the GC-ECD. By this method at a fortified OA concentration of 10 ng/g, the recovery was in ther range of 89% similar to 118%. LOD was 1.7 ng/g tissue (GC-ECD). Average OA content in normal cockroach was 68.49 +/- 7.31 ng/g tissue.