Methods for Collection and Analysis of Semiochemicals

Most of the methods that have been used to collect or extract pheromones from true bugs are analogous to methods used with insects in general, and will be summarized here only briefly. The interested reader is referred to several reviews [4,12-14]. First, whole insects or body sections have been soaked in solvent (e.g., N. viridula [15] Campylomma verbasci [16]). However, the value of whole body extracts is questionable because of their complexity, and the bulk of the compounds obtained may be unrelated to the pheromone components, hampering further investigation of the actual pheromone. 

More recently, solid phase microextraction (SPME) [22] has been applied to the analysis of bug pheromones, using two techniques. In the first, headspace volatiles are trapped on the SPME fiber, analogous to trapping on SuperQ [e.g., 23]. Alternatively, if the source of the pheromone is known, the SPME fiber can be wiped on the cuticle to directly adsorb the compounds [24]. In either case, the fiber is then thermally desorbed directly into a GC or GC-MS. Whereas this method is excellent for analysis, with good recoveries, it does not provide a sample that can be used for bioassays or for isolation of an active compound. 

All extract preparation and analysis methods have biases and potential weaknesses. For example, most of the methods described above recover polar, water-soluble compounds poorly if at all, very volatile compounds may be obscured by solvent peaks during analysis, or compounds may degrade during extraction or analysis (e.g., [25]). 

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