Examination of the Gas-Vapour Phase of Cigarette Smoke. 2nd Report: The Determination of the Carbon Monoxide Content of the Gas Phase of Cigarette Smoke - Zur Untersuchung der Gas-Dampf-Phase des Cigarettenrauches: 2. Mitteilung: Zur Bestimmung des Stickstoffmonoxids (NO) aus der Gasphase des Cigarettenrauches

The NO content of the gas-vapour phase of cigarette smoke is determined by a simple colourimetric procedure: NO is absorbed by a solution of FeSO₄ in diluted H₂SO₄ up to an equilibrium with the formation of the addition compound Fe•NO•SO₄. The spectrophotometric investigation of the resulting solution shows two maxima (580 and 445 mµ). The maximum at 445 mµ is chosen for the colourimetric determination of NO. The formation of Fe•NO•SO₄ takes place via a reversible stoichiometric reaction, the absorption of NO is proportional to the partial pressure of NO in the gas mixture. The concentration of NO in the mainstream smoke of commercial cigarettes with different tobacco types and blends has been shown to be in the range between 250-1500 ppm, i.e. 110-660 µg NO/ cigarette. Contrary to other methods, the new procedure enables the differentiated determination of NO besides NO₂. In the fresh smoke from Straight Virginia cigarettes, i.e. 2-5 sec. after generation, no NO₂ was detectable. Under the same conditions, blended cigarettes showed a content of about 5 µg NO₂/cigarette. 60 seconds after smoke generation, about 200 µg NO₂/cigarette have been determined. These results show that of the nitrogen oxides only NO is present in fresh cigarette smoke. The autoxidation to NO₂ occurs to a considerable extent within 60 seconds