Determination of Hydrogen Cyanide in Cigarette Smoke by Continuous Flow Analysis Method Using Safer Chemistry

A new safe and sensitive method to determine hydrogen cyanide (HCN) in cigarette smoke using continuous flow analyser (CFA) has been developed and validated. The use of highly toxic potassium cyanide (KCN) as a standard necessitates the development of a safer method for the determination of HCN in cigarette smoke. In this described method KCN is replaced by less toxic potassium tetracyanozincate (Lethal Dose LD₅₀ oral is 7.49 mg/kg for KCN and 2000 mg/kg for potassium tetracyanozincate). Furthermore, the new method uses isonicotinic acid-barbituric acid (coupling reagent) instead of pyridine-pyrazolone as a reagent for the determination of HCN, and hence eliminates the use of pyridine. In this method HCN is trapped on both the Cambridge Filter Pad, then extracted with aqueous sodium hydroxide solution, and in an impinger containing the same solution. The solution thus extracted is oxidised to cyanogen chloride by Chloramine-T and treated with coupling reagent, the resulting stable chromophore was measured colorimetrically at 600 nm. The regression equation was linear in the range of 1 to 25 μg/mL for cyanide with a correlation coefficient (R²) > 0.9998. The limit of detection (LOD) was 0.76 μg/cig and the overall relative standard deviation (RSD) of the method was less than 10%. Excellent recoveries of cyanide were obtained in the range from 92% to 112% and the HCN yields from the Kentucky Reference Cigarette 3R4F obtained from the newly developed method are in good agreement with those from the conventional KCN method. The proposed method is robust, reliable, selective and safer than any of the existing methods for determination of hydrogen cyanide in mainstream as well as in sidestream cigarette smoke.