A VERSATILE AND QUANTITATIVE VOLATILE-DELIVERY SYSTEM FOR LABORATORY BIOASSAYS

A versatile moving-air system is described for delivering volatiles in to a wind tunnel or other bioassay device. The system controls up to f our volatile sources at one time. There is a calibrated, adjustable sp litter for each source so that any percentage of a source's airstream, or none of it, can be directed to the system outlet at any moment. Th us, the system allows the sample volatiles to be bioassayed in any ord er and at any level or in mixtures of any desired proportions. Volatil e sources of many types can be used, including single chemicals in slo w-release formulations, mixtures of chemicals, or volatiles from livin g organisms. The volatile stream can be sampled by solid-phase microex traction (SPME) just before it enters the wind tunnel. Analysis of the SPME sample by gas chromatography allows absolute delivery rates of v olatile components to be calculated. System performance was characteri zed with physical measurements and with bioassay experiments involving Carpophilus humeralis (F.) (Coleoptera: Nitidulidae). One bioassay ex periment demonstrated how volatiles from a microbial culture (fermenti ng bread dough) and a synthetic counterpart (an aqueous solution of ac etaldehyde, ethanol, I-propanol, isobutanol, 3-methyl-1-butanol, 2-met hyl-1-butanol, and ethyl acetate) could be compared at a range of dose levels, with just one sample of each type. These natural and syntheti c volatile sources delivered very similar amounts of the above compoun ds and produced nearly identical dose-response curves. In another expe riment, three bread dough volatiles (ethanol, acetaldehyde, and ethyl acetate) were tested in mixtures. Each component was used at four diff erent levels (giving a total of 64 experimental treatments), but just one physical sample was needed for each chemical. The experiment provi ded clear information about response thresholds and interactions among these host volatiles. The volatile delivery system is versatile, easy to operate, and can be constructed from inexpensive materials.