Background

Smoking is the major risk factor of mortality in the world according to the statistical information; the cigarette consumption during one century has increased over 100 times, which increases the concern over the safety of tobacco products [1, 2].

Tobacco smoke contains more than 5000 chemical compounds which 150 of these substances have been proved to be toxicants [3, 4]. Hydrogen cyanide is one of the tobaccos smoke poisonous substances which are formed from the combustion of the protein and nitrate compounds existed in tobacco at high temperatures in the oxygen deficient condition [5, 6] which it’s chronic and low exposure causes neurological, respiratory, cardiovascular and thyroid effect [7–9].

The tobacco smoke pathway includes the part directly entered the mouth called mainstream and the part diffused in the surrounding, called side stream, which hazardous for nonsmoker. The level of HCN in mainstream smoke is ranged from 10 to 400 μg per cigarette (US Brands) which 0.6 to 27 % of these amounts exist in side stream smoke [10]. In the previous study the level of HCN in the non-filtered cigarette was between 400 to 500 μg per stick [11] and in another study the amount of HCN in the mainstream smoke of cigar, non-filtered cigarette and filtered cigarette was 1035, 59 and 448 μg per 1 g of tobacco, respectively and in small cigars it was between 510 to 780 μg per 1 g of tobacco [12].

There are different reported methods determine HCN in different samples including voltammetry [13], fluorometry [14, 15] gas chromatography [16], LC-MS-MS [17], HPLC-MS [18], potentiometry [19], spectrophotometry [20] and colorimetry [21]. Among them, polarography the subclass of voltammetry is the most precise and inexpensive method based on the oxidation and reduction mechanism [22].

The aim of this study is focused on the determination of the HCN in mainstream smock of different brands of cigarette consumed in Tehran using polarography method.

Materials and methods

Collection of samples

A total of 50 types of different brands of the most consumed or available cigarettes (47) and cigars (3) were collected from local stores at September 2012. The 20 % of the samples were from Winston company, 18 % from Marlboro, 6 % from Magna, 8 % from KENT and 8 % from local or officially imported companies and the rest, 40 % are from a different companies (as shown in Table 1).

Table 1 Hydrogen cyanide concentration and price of different brands of cigars
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Reagents and chemicals

All chemicals used were of analytical reagent grade from Merck (Germany). Buffer solutions were prepared by dissolving boric acid (0.2 M) and potassium hydroxide (0.17 M) in 1000 ml ultrapure water and adjusting the solution to pH 10.2. Cyanide standard solution (1 g/L) was prepared by dissolving 0.2503 g KCN in 100 ml KOH 0.01 M in ultrapure water.

Apparatus

Analysis was conducted by the Metrohm Polarography device 797 VA Computrace, three electrode systems consisting of a dropping mercury electrode (DME) as the working electrode, an Ag/AgCl reference electrode and platinum counter electrode. The device outfitted in the following conditions: stirrer speed 2000 rpm, mode DP, purge time 300 s, equilibration time 5 s, pulse amplitude 50 mV, start potential 0 V, end potential −500 mV, voltage step 8 mV, voltage step time 0.8 s, sweep rate 10 mV/s, peak potential CN −240 mV. All instrumental settings were those recommended in the manufacturer’s manual book and the instrumental conditions with the method of AB110-Det of cyanide [23]. All potentials quoted were measured against an Ag/AgCl reference electrode and the polarographic cell volume was 20 ml.

Method of analysis

The HCN in each cigarette and cigar mainstream smoke were collected using mainstream apparatus (Fig. 1) [24, 25]. The cigarette was applied to the entrance station and suction force obtained by the vacuum pump simulate the human inhalation and extract the tobacco smoke, the flow of smoke were passed through the glass tube filled with 100 ml NaOH (0.1 M) solution to entrap HCN as CN− ion.

Fig. 1
figure 1

Cigarette mainstream collecting apparatus

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Subsequently, the mixture of above mentioned solution contain cigarette smoke (10 ml) and buffer solution (10 ml) was added to the polarographic vessel and deoxygenated for 10 min with high-purity nitrogen and achieved the peak of CN− in the range of −0.5-0 V. To determine the CN− concentration by standard addition method, 50 μl cyanide standard solution was added (two times) and the polarogram was obtained (Fig. 2).

Fig. 2
figure 2

The differential pulse polarogram of cyanide ion in cigarette smoke sample. a the peak of sample solution b the peak of first dilution of standard addition c the peak of second dilution of standard addition

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Statistical analysis

All statistical analyses were performed using the statistical software for social sciences (SPSS Inc. Chicago, IL, Version 21). Statistical analyses of each sample were characterized by mean ± standard deviation. The mean levels of cyanide were compared across categories of price, and weight of each cigarette or cigars. The significance level was defined at 0.05 for the regression equations.

Result and discussion

The result of mainstream smoke HCN determination by polarography (Table 1) showed that among 50 samples the average amount of HCN was 184.825 μg per stick which the highest level of HCN pertain to Jewel sweet cigar, 1553.98 ± 0.56 μg per cigar, and the lowest was Swiss Marlboro with 17.56 ± 1.02 μg per cigarette. Moreover, the average amount of HCN in cigarettes and cigar were 218 μg and 785.09 μg, respectively, In addition the average weight of cigarette and cigar samples was 800 mg and 5500 mg, respectively, and the average weight of whole samples was 1084.24 mg.

The changes in the HCN levels are dependent on the preparation procedure of tobacco, which lead to the diverse amount of proteins and nitrate compounds of cigarette which render the conversion of HCN level emission. In addition it may be possible to assess the quality of cigarette especially ultralight by determining the amount of HCN as it is increased in the unfeigned products.

Furthermore, based on our study there is no connection between price, weight and appearance of cigarette, cigar and HCN level. For instance, Jewels sweet and PHILLIES BLUNT cigars have the same price, but different level of HCN doesn’t necessarily cause the higher HCN level emission. The regression method was applied for the development of the mentioned model. Validation of the method was conducted by analyzing the different set of independent data from the same source. As can be seen the R2 which is a statistical measure of how close the data are to the fitted regression line is low (0.20) (Fig. 3). So it means the model is useless for prediction based on cigar and cigarette weight and its price.

Fig. 3
figure 3

The relationship between cyanide, weight and price each of cigarettes

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In addition, previous studies demonstrated that even exposure to lower concentrations of cyanide may result in a range of non-specific features include headache, dizziness, throat discomfort, chest tightness and eye irritation which these symptoms would grow by more substantial exposure [26–28]. Moreover the results of our study indicate that cyanide concentration of all samples, even light cigarette is above established levels for chronic toxic doses [9] (Fig. 4).

Fig. 4
figure 4

Cyanide concentrations in different kind of Cig

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Conclusions

In this study, HCN of the toxic components of the tobacco smoke was determined by polarographic method. The results shows that the ranges of HCN level of 50 samples were varied between 17.56 ± 1.02 - 1553.98 ± 0.56 μg per stick. This acquired amount is more than FDA approval (10 μg per stick).