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Three modified β-cyclodextrin (CD) and two α-CD phases were used at 125 and 150°C to gas chromatograph 22 diverse oxygen-containing substances from volatile oils. Percentage changes with temperature in retention times relative to n-undecane were determined. Solutes showing significant decreases include acyclic geraniol and citronellol, plus three cyclic alcohols. A smaller decrease than the average 90%, or even an increase in relative retention on some phases was shown by three non-alcohol bicyclics and menthone, all saturated molecules. At 125°C, results are compared for pairs of β-CDs, the dipentyl modification proving very useful. Percentage increases in relative retentions observed against hydroxypropyl-dimethyl- or trimethyl-CDs could indicate solutes to be an alcohol (bicyclic, monocyclic or acyclic), another type of bicyclic, an aromatic or a carbonyl compound. The two methods offer good structure indications for unknown solutes using either temperature changes on one CD phase, or on two phases at one temperature. |
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