Chemical Studies on Tobacco Smoke. IX: Quantitative Analysis of Chlorinated Hydrocarbon Insecticides

Abstract

Abstract An analytical method was developed for the qualitative and quantitative determination of chlorinated hydrocarbon insecticides in tobacco products. It is based on three consecutive liquid-liquid distributions, followed by column chromatography on deactivated alumina. This procedure leads to a degree of enrichment which permits the direct assessment of the insecticides by gas chromatography. For the isolation and identification of the individual components the column chromatography endfractions are separated by gas chromatography and collected from the effluent of the column. These materials are used for mass spectrometric analysis. For the quantitative analysis C14-labelled DDT is employed as internal standard and the amount of insecticides is determined with the aid of a gas chromatograph with an electron capture detector with a sensitivity for chlorinated insecticides of 1 nanogram (10-9 g). In 1.0 g cigarette tobacco were found 11.7 µg 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane [DDD]; 4.8 µg 1,1-dichloro-2-(o-chlorophenyl)-2-(p´-chlorophenyl)ethane [o,p´-DDD]; 7.8 µg 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane [DDT] and 3.6 µg of an admixture of 1,1,1-trichloro-2-(o-chlorophenyl)-2-(p´-chlorophenyl)ethane [o,p´-DDT] and 1,1-dichloro-2-(m-chlorophenyl)-2-(p´-chlorophenyl)ethane [m,p´-DDD]. The mainstream smoke of an 85 mm U.S. blended cigarette without filter tip contained 1.75 µg DDD, 0.45 µg o,p´-DDD, 0.81 µg DDM, 0.77 µg DDT, 0.70 µg o,p´-DDT plus m,p´-DDD, 0.21 µg 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene and 0.21 µg 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene [DDE] and 1.52 µg trans-4,4´-dichlorostilbene [trans-DCS]. Endrin was neither detected in cigarette smoke nor in commercial U.S. tobacco samples purchased during the winter 1967-68. The transfer rates for unchanged chlorinated insecticides from cigarette tobacco into mainstream smoke were 18 % for DDD, 11.6 % for o,p´-DDD and 12.4 % for DDT. The extraction of tobacco with n-hexane does not yield a complete extraction of chlorinated insecticides. A study in which a single leaf of a tobacco plant was sprayed with C14-labelled DDT indicated that the insecticide to some degree permeates the tobacco plant by diffusion into the lower layers of the leaf. In tobacco smoke condensate, which is exposed to sunlight or white laboratory light, one pyrolysis product of DDD and DDT, trans-4,4´dichlorostilbene, is photoisomerized to its cis-isomer. In an in vitro test cis-4,4´-dichlorostilbene was found to be dehydrogenated in air up to 0.5 % to 3,6-dichlorophenanthrene. Pyrolysis experiments at 880°C with DDD and DDT have been discussed briefly. In addition to components already found in cigarette smoke, chlorobenzene, the highly reactive 9-methylenefluorene and tentatively 1-chloro-2,2-(p-chlorophenyl)ethane as well as 3,6-dichloro-9-chloromethylfluorene were identified in the pyrolyzate. The findings of this study are compared with earlier investigations and discussed in respect to the formation of some of the chlorinated aromatic hydrocarbons. Animal studies are needed to evaluate the possible tumorigenicity of the major pyrolysis products of DDT and DDD.