Determination of N-Nitrosodimethylamine in the Smoke of High-Nitrate Tobacco Cigarettes

A gas chromatographic method was developed for the determination of N-nitrosodimethylamine (NDMA) in cigarette smoke. The NDMA in the smoke of 200 cigarettes was trapped in a solution of sodium hydroxide and separated from most of the smoke components by distillation from acidic and basic solutions. The aqueous solution was extracted for 8 hr. into ethyl ether in a Dean Stark apparatus. To concentrate the solution of NDMA, the ether was distilled until only 5 ml of the solution remained. An aliquot of this solution was analysed by means of a gas chromatograph equipped with a 200-ft. glass capillary column coated with Carbowax 20-M poly(ethylene glycoI). An alkali metal flame ionization detector with a selectivity of 10*/1 for nitrogen compounds to normal hydrocarbons was used. Small amounts (2 ng) of nitrosamines in the presence of large amounts of other compounds were easily detected. N-nitrosodimethylamine-C¹⁴ was used as an internal standard. The recovery of the method was 50 to 60%. The smoke of cigarettes made from a high-nitrate Burley tobacco and from a tobacco blend containing 8% NaNO₃ contained 50 ng and 95 ng of N-nitrosodimethylamine per cigarette, respectively. Positive identification of NDMA in the smoke of these cigarettes was made by mass spectrometry. No NDMA was found in the smoke of two popular domestic cigarettes or in a cigarette composed of a blend of Burley tobaccos. The limit of detection of the method is 10 ng/cigarette; therefore, if NDMA is present in the smoke of these domestic cigarettes, its concentration is less than 10 ng/cigarette.