DYNAMIC HEADSPACE ANALYSIS OF FLORAL VOLATILES - A COMPARISON OF METHODS

Lack of standardization of floral scent analysis using dynamic headspa ce collection and GC-MS has prevented meaningful biological comparison s of results from different studies. We explored technique-related sou rces of variation by comparing the relative performances of different trapping sorbents, elution solvents and vacuum pump flow rates in the collection of known volatiles from (a) synthetic blends on filter pape rs and tb) living Bowers of Clarkia breweri (Onagraceae). The greatest amounts of volatiles were collected when Porapak Q sorbent and hexane solvent were used, but most analyses were qualitatively similar. Low and high pump flow rates yield a tradeoff, with higher rates trapping low volatility compounds but also raising ambient contamination levels . Significant variation was associated with the use of different sorbe nts and solvents, but detailed statistical comparisons were precluded by significant interaction effects involving-other experimental variab les. Given the tightly controlled experimental conditions and use of i nbred plant lines, this unexpected result suggests that analyses of sm all samples carry a high risk of experimental artifact. We recommend t hat floral scent analyses incorporate experimental and statistical app roaches that address as many method-related variables as possible, tha t samples of 10 or more individuals be used, and that GC-MS parameters be held constant for all comparative analyses.