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A capillary GC method has been developed to analyze laboratory or commercial samples of the medfly attractant ceralure [ethyl 4- (and 5-)iodo-trans-2-methylcyclohexane-1-carboxylate]. The method utilizes a specially prepared fused-silica column with a bonded phenyl-methyl polysiloxane liquid phase. Baseline separation was achieved for three of the four trans-ceralure isomers. Difficulties encountered with other columns investigated are also discussed.

CIC-4 (1,1,4,5,6,7,8,8a-octahydro-3H-2-benzopyran-3-one) is a fused bicyclic lactone which acts as a non-contact insect repellent for Aedes aegypti at 1% concentration in 95% aqueous ethanol when applied topically to rhesus monkeys. Chromatographic and spectroscopic analyses of a synthetic sample indicated the presence of cis-and trans-fused isomers. To supply each isomer for the assessment of mosquito repellent efficacy on humans, we developed a semi-preparative high-performance liquid chromatographic separation technique for the isomer separation. A column of 5-μm silica was used for isolating milligram quantities of each isomer. By this method, each isomer was obtained in > 95% gas-liquid chromatographic (GLC)-purity for biological evaluation. Supporting GLC and electron impact and chemical ionization gas chromatography-mass spectrometric data are also presented for each isomer. Biological evaluation on the human arm using Anopheles quadrimaculatus, Aedes aegypti, and Anopheles albimanus as the test species was effective in determining relative repellency to the standard N,N-diethyl-3-methyl-benzamide