4.2.3.1. Analysis

Nowadays, the most used method for HC identification is mass spectrometry coupled to gas-chromatography (see section 2.2.4 for more details on GC-MS analysis), although satisfactory results can be obtained also using stand-alone gas-chromatography using the retention index method. In this case, peaks in the chromatogram are identified according to their retention index that is calculated from the retention time of the peak and that of adjacent reference alkanes. .For the analysis, 0.1 insect equivalent (i.e. 1/10 of the material that can be extracted from a single insect) in 1 µl of hexane can be injected in the chromatograph (injector temperature can be set to 300 °C) in splitless mode. A capillary column is normally used; many authors found DB-5 or DB-1 columns particularly suited for the purpose. The temperature of the GC is ramped from 40-50 °C to 300-320 °C and maintained at that temperature for 20 minutes or more.

The compounds in the extracts are identified by comparison of retention times and spectra (if GC-MS is used) with those of authentic standards. Quantification is based on the peak area with reference of that of the internal standard; a standard solution of hydrocarbons should also be analysed to calculate calibration factors. For more details on quantitative analysis see section 2.2.4.1.2

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