JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY, MARCH 1993, VOL. 8 253

Determination of Cadmium, Cobalt, Iron, Nickel and Lead in Venezuelan Cigarettes by Electrothermal Atomic Absorption Spectrometry*

Jos6 Alvarado and Ana Rita Cristiano Departmento de Quimica, Universidad Simon Bolivar, Apartado 89.000, Caracas 1080-A, Venezuela

An electrothermal atomic absorption spectrometric method for the determination of Cd, Co, Fe, Ni and Pb in the constituent parts of Venezuelan cigarettes before and after smoking, is described. Rapid and convenient sample treatment was achieved by means of microwave wet acid digestion. Analyses were performed under optimized conditions using deuterium arc background correction. Atomization was carried out using the L’vov platform and tube-in-tube techniques. Similar accuracy, sensitivity and precision were obtained with both types of atomizer, but the latter provided a longer useful lifetime. Relative standard deviations for aqueous standards of the analyte of interest ranged from 0.66 to 1.28%. Detection limits, in pg ml-l, were 3.87 x for Co, 9.64 x 1 0-4 for Ni and 5.34 x 1 0-4 for Pb. The detection limit for Fe, determined at 373.7 nm, an absorption line less sensitive than the resonance line, was 5.04 x 1 0-2 pg ml-l. The accuracy of the results was checked against National Institute of Standards and Technology Standard Reference Materials and by recovery studies. The results show that Venezuelan cigarettes contain trace metal concentration levels that are similar to those in foreign cigarette brands. Most of the trace metal content found was in the tobacco, with Fe at the highest concentration followed by Pb, Nil Cd and Co. Keywords: Electrothermal atomic absorption spectrometry; L ’vov platform; tube-in-tube; cigarette analysis; cadmium, cobalt, iron, nickel and lead determination

for Cd, 8.03 x

It is well known that trace metals play an important role in human metabolism1 and either an excess or a deficiency of certain metals in the organism can lead to biological disorders, which may include anaemia, some particular forms of cancer and even Cadmium and Pb are particularly toxic and Co, Fe and Ni can become highly toxic if inhaled as carbonyl c ~ m p o u n d s . ~ * ~ Possible sources of toxic metals include food, beverages and the living and working environment. For smokers, cigarettes may consti- tute an additional source of toxic metals. If Cd and Pb are present in the filter, paper or tobacco of cigarettes, they may be inhaled during smoking. If Co, Fe and Ni form stable carbonyl compounds, as mentioned by Iskander et al.,4 at the temperatures at which tobacco and paper burn they may also reach the lungs of smokers.

Tobacco has been extensively studied in order to assess the effect of nicotine on the human b ~ d y . ~ , ~ Some attention has also been given to the determination of toxic metals in the constituent parts of cigarettes.’-” Most of the work concerned with the determination of toxic metals in cigarettes has been carried out using neutron activation analysis. However, this technique is not the best choice for the determination of Cd and Pb because they do not have easily measurable isotopes. l8 Flame atomic absorption spectrometry has also been used in this type of analysis, particularly in the determination of Cd in seedlings and mature tobacco plants’ and in Indian flue-cured tobacco 1ea~es.l~ Unfortunately, these studies did not provide details of the atomic absorption methodology used. To our knowledge, electrothermal atomic absorption spectrometry (ETAAS) has not been applied to the measurement of the toxic metal contents of all the constituent parts of cigarettes. In this paper, the application of ETAAS to the determination of Cd, Co, Fe Ni and Pb in the different constituent parts of cigarettes before and after smoking is described.

*Presented at the Second Rio Symposium on Atomic Absorption Spectrometry, Rio de Janeiro, Brazil, June 21-28, 1992.

Experimental Instrumentation A tomic absorption apparatus The atomic absorption measurements were made on a Perkin-Elmer Model 2 380 spectrometer equipped with an HGA-400 graphite furnace atomizer and a deuterium arc background correction system. Manual sample injection was achieved by means of Eppendorf micropipettes with disposable plastic tips.

Microwave oven A National Panasonic NE 6660 domestic microwave oven, provided with a variable timing cycle, a variable heating cycle with power settings from ‘warm’ to ‘high’ (60-600 W) and a rotating tray, was used for the microwave digestions. The sample containers used for microwave digestion have been described p r e v i o ~ s l y . ~ ~

Reagents Standard reference materials and cigarette samples National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs) 157 1 Orchard Leaves, 1573 (Tomato Leaves), 1 575 Pine Needles and 1633a Trace Metals in Coal Fly Ash were used to check the accuracy of the determinations. The four most popular Venezuelan cigarette brands (coded A-D) were selected for this study. Twenty packets of each brand, each containing 20 cigarettes, were purchased at ten different local suppliers.

Stock and working standard solutions Standard reference solutions for calibration and optimiza- tion of the analytical conditions were prepared by conven- tional dilution of Merck stock solutions containing 1000 pg ml-l of the analyte as nitrate. Inorganic acids and other chemicals used were of analytical-reagent grade. Distilled, de-ionized water (specific resistivity 18 MR cm-l) from a

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254 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY, MARCH 1993, VOL. 8

Millipore water purification system was used for the preparation of samples and standards.

Analytical Procedure Sampling The twenty packets of cigarettes of each brand were divided into two groups, each containing 10 packets or 200 cigarettes. One group was used for the analyses of the components (filter, tobacco and paper) before smoking. The cigarettes were separated into their components by means of stainless-steel tweezers covered with Teflon. The ciga- rettes in the second group were completely ‘smoked‘ using the assembly shown in Fig. 1. When the tobacco and wrapping paper of the cigarettes was about to be totally burnt, the one-way valve of the smoking machine was closed and the vacuum pump stopped so as not to burn the filters. Thus, sufficient and representative samples of tobacco, paper, ash, and used and unused filters were obtained for analysis.

Sample pre- t reat men t Pooled samples of tobacco and ash of each cigarette brand were homogenized by exhaustive manual mixing, using a spatula. A 10 g amount of the former and 2 g of the latter were manually ground in separate agate mortars to a powdery texture. No granulometric analysis was carried out, The finely ground tobacco and ash and the NIST standards, as received, were dried in air at approximately 85 “C for 12 h and kept in desiccators before being analy sed.

Microwave sample dissolution Tobacco. Three 0.2 g portions of the ground, homogenized and dried tobacco sample of each individual cigarette brand were placed in separate test-tubes. To each test-tube 2.5 ml

a- Cigarette

8.8 t cm

0.5 cm’ I Nitric acid ’ solution

-Vacuum

Fig. 1 Assembly used for collection of ashes and metals from cigarettes

of concentrated nitric acid and 0.5 ml of concentrated hydrofluoric acid were added and the tubes were tightly capped. The twelve test-tubes were then individually irradiated at the ‘medium low’ (40% of maximum power) setting of the oven for 1 min. The dimensions of the microwave oven cavity and the need to contain the test- tube inside a large plastic container, which could act as a vapour sink in the event of rupture of the tube,19 did not allow for irradiation of several samples at the same time. A 3 min cooling period in a water-bath was allowed after each heating period to avoid excessively high pressures inside the test-tubes. Experience had shown that heating periods of longer than 1 rnin could lead to rupture of the tube’s cap, resulting in vapour leakages and losses of the analyte. After heating for 15 min (fifteen 1 rnin pulses), the samples were cooled to room temperature, filtered at atmospheric pres- sure through a Whatman No. 42 filter-paper and diluted to 25 ml with distilled, de-ionized water.

Wrapping paper. For each cigarette brand, the wrapping papers from five cigarettes, each sheet weighing approxi- mately 35 mg, were taken with Teflon-covered tweezers and pressed into the bottom of a test-tube. Twelve test-tubes (three per cigarette brand) were prepared in a similar fashion. To each test-tube 1.5 ml of concentrated nitric acid were added and then the tubes were tightly capped and submitted to microwave heating at the ‘medium’ (60% of the maximum power) setting of the oven as described above. After heating for 10 min, the samples, competely dissolved, were cooled to room temperature and diluted to 10 ml with distilled, de-ionized water.

Ash. Three 0.2 g portions of ground, homogenized and dried ash from each different cigarette brand were placed in test-tubes. Concentrated nitric acid (2.5 ml) and concen- trated hydrochloric acid (1 ml) were added to each tube. The 12 test-tubes were tightly capped and individually microwave heated at the ‘medium low’ setting of the oven, as described above. After heating for 7 min, the tubes were cooled to room temperature, 0.5 ml of hydrofluoric acid was added to each test-tube and the heating was continued for an additional 3 min. The samples were then cooled to room temperature, filtered and diluted to 25 ml with distilled, de-ionized water.

Filters. Three unused filters, randomly taken from each cigarette brand, were placed in separate test-tubes. To each tube, containing three filters, 2.5 ml of concentrated nitric acid and 1 ml of concentrated hydrochloric acid were added. The 12 test-tubes were individually microwave irradiated at the ‘medium low’ setting of the oven as described above. After 15 rnin of heating, the samples were cooled to room temperature, filtered and diluted to 25 ml with distilled, de-ionized water. The same procedure was applied to used filters, which remained after the cigarettes had been ‘smoked’ (see below). In both instances, solid residues trapped in the filter-paper were saved for subse- quent analysis.

NIST Standard Reference Materials. The NIST SRMs 157 1 Orchard Leaves, 1573 Tomato Leaves and 1575 Pine Needles were treated following the procedure described for the tobacco samples. The NIST SRM 1633a Trace Metals in Coal Fly Ash was heated according to the procedure followed for the cigarette ash.

Smoke The smoke from five cigarettes, randomly selected from

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JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY, MARCH 1993. VOL. 8 255

each of the brands, was collected using the assembly shown in Fig. 1. For this purpose, lighted cigarettes were sequen- tially inserted into the internal glass tubing of the assembly and gentle suction was initiated, via the lateral arm of the external glass cylinder, by means of a vacuum pump. Opening and closing the one-way stopcock valve attached to the lateral arm allowed for ‘smoking’ of the cigarettes at certain intervals which attempted to simulate normal smoking conditions.20 The smoke thus produced was aspirated into four separate 3 ml solutions of concentrated nitric acid, thus allowing for the trapping of the metals of interest in the acid solution.

0.200

0.150 Q)

C

2 0.100

9 2

0.050

Results and Discussion Digestions Several acid mixtures in various ratios and several combina- tions of time and power settings of the microwave oven were investigated in an effort to achieve efficient and rapid digestion of the samples. A trial and error approach was followed for these tests. The main aim was to achieve total dissolution of the samples or, if that was not possible, to obtain the maximum extraction of the analytes into the aqueous phase, in the shortest time and with the minimum amount of acids. These two last factors were of importance as they control the speed of analysis, the blank signals and the corrosive effects of the sample on the graphite atomizer. As the sample treatment time and the amount of acid or acid mixtures needed depend on the amount of sample treated, the sample size was restricted to that amount which could be accurately weighed, could be dissolved or extracted in a convenient volume and which produced easily measurable atomic absorption signals (within the linear dynamic range) of each element. For these first tests, the amount of acid or acid mixtures used for digestion was not optimized. In fact, they were always in great excess in order to speed up the digestion of the samples or extraction of the elements.

Once the optimum amount of sample was defined, according to the criteria described above, further tests were carried out to select the minimum amount of acid or acid mixture needed for treatment of that amount of sample and to define the final volume of the sample solutions. Solutions having around 200 mg of tobacco or ash and around 800 mg of filter samples (i.e., three filters) in a total volume (acid plus water) of 25 ml were found to be adequate for analysis. In the particular case of wrapping paper samples, dissolu- tion of five paper wrappings (approximate mass 180 mg) in a total volume of solution of 10 ml produced easily measurable signals for most of the analytes. The exception was Co in paper from cigarette brands B, C and D. Increasing the sample size to ten paper wrappings did not improve the results for Co. Treatment of more than ten wrappings required excessively large volumes of acid to cover the sample adequately for efficient acid attack. Moreover, the sheer bulk of the sample made dissolution impractical using the microwave sample containers avail-

0 5 10 15 20 25 Digestion timelmin

Fig. 2 Absorbance versus microwave digestion time for Cd in tobacco

able. Therefore, the sample size for the analysis of wrapping paper was limited to five wrappers.

Wrapping paper samples were totally dissolved using the experimental conditions already described. The tobacco, filter and ash samples left solid residues, probably barium sulfate (which is added to the tobacco leaves to control their combustion8) and/or silicon compounds,*l no matter which acid combination or microwave heating conditions were used. In these instances, and in order to achieve the best extraction of each analyte into the aqueous phase in the shortest time possible, a study of maximum extraction of the analyte as a function of digestion time was performed. For this study the acid combinations and microwave power settings previously found to have produced less solid residues were used. The digestion time that resulted in solutions that gave the maximum absorbance signal for each analyte, as represented in Fig. 2 for Cd, was taken as optimum. For these tests, microwave heating was carried out in a pulsed fashion similar to that described under Experimental. Table 1 summarizes the experimental condi- tions used for the microwave acid treatment for each type of sample.

Efficiency of Sample Treatment As explained above, the tobacco, ash and filter samples were not completely dissolved by the microwave wet acid treatment. The fact that the analyses of SRMs, having matrices similar to tobacco and ash and treated in a similar manner to the cigarette samples, produced results that were in good agreement with the certified values was taken as an indication of total extraction of the metals of interest during the microwave heating of tobacco and wrapping paper samples under optimized conditions. To check further whether the solid residues left by the filter samples contained the metals sought, the residues were qualitatively analysed by means of X-ray fluorescence spectrometry. The spectra obtained showed characteristic peaks for Cu, which

Table 1. Experimental conditions for the microwave acid treatment of tobacco, wrapping paper, ash and filter samples

Microwave oven setting Heating Sample Acid Volume/ml (% of maximum power) time/min

Tobacco HNO, HF

Wrapping paper HNO3

Ash

Filter

HNO3 HCl HF

HNO, HCl

2.5 0.5 1.5

2.5 1 0.5 2.5 1

Medium low 15

Medium 10

Medium low 10

(40)

(60)

(40)

Medium low (40)

15

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256 JOURNAL OF ANAILYTICAL ATOMIC SPECTROMETRY, MARCH 1993, VOL. 8

could be due to the Cu content of the collimator used in the instrumental set-up, and the peak corresponding to Ag, which is the final product of degradation of lo9Cd used as the irradiation source. No indication was obtained of the presence of Cd, Co, Fe, Ni or Pb. Therefore, it can be concluded that no appreciable amounts of the analytes were left in the filter residues.

Feasibility of Using the Tube-in-Tube Technique The tube-in-tube atomizer consisted of a combination of an external pyrolytic graphite coated graphite tube (2.8 cm long x 0.5 cm i.d. x 0.7 cm 0.d.) containing a very thin (wall thickness less than 0.1 cm) inner tube made of pure pyrolytic graphite measuring 1.8 x 0.4 cm 0.d. A graphite wedge, obtained from a broken pure pyrolytic graphite tube, was used to keep the internal tube positioned in such a way that the dosing holes of both tubes coincided. The wedge also served to minimize the contact between the external walls of the inner tube and the internal walls of the outer tube. Hence, heating of the inner tube was accom- plished mainly by radiation coming from the internal walls of the outer tube.

Several measurements, using the heating conditions shown in Table 2, were carried out to compare the atomization performances of the L'vov platform and the tube-in-tube technique. Detection limits, repeatability and useful lifetime were checked for both types of atomizers using aqueous solutions of Cd and Fe. These elements were chosen on the basis of their volatility, Cd being the most volatile and Fe the least volatile of the elements considered in this work. Before initiating any analytical measurements the brand new tubes and platforms were pre-conditioned as

proposed by the manufacturers.22 Similar detection limits i3nd repeatability values were found in both instances.

An appreciably longer useful lifetime, with an average of 50 more heating cycles, was obtained for the tube-in-tube atomizer compared with platform atomization. Breakage of the graphite tubes was the criterion taken to define the useful lifetime of both types of atomizers. Under the heating conditions used, platform atomizers lasted for ;€bout 400 heating cycles for Fe and about 500 heating cycles for Cd, whereas the tube-in-tube atomizers lasted for about 450 cycles for Fe and about 550 cycles for Cd. This behaviour is to be expected on the basis of the higher temperatures at which Fe was charred and atomized in both instances and to the more corrosive effect of Fe than Cd.23 The sensitivity and repeatability of the measurements began to deteriorate when the atomizers were close to breakage. Observation of the tubes after 350 heating cycles, before breakage, showed the area around the dosing hole in Ihe platform tubes to be extensively scaled, whereas in the 1 ube-in-tube atomizers that area, although affected, seemed 1.0 be in better condition. It is probable that the presence of 1he inner tube helped to reduce the contact of the acid vapours on that area of the external tube, thus reducing lheir corrosive effect. As breakage of the tubes always occurred at the middle of the tube, the above argument could be an explanation for the longer useful lifetime observed for the tube-in-tube atomizers. Given these results, the tube-in-tube approach was adopted for subse- quent measurements.

Ihaluation of Analytical Performance Except for the Fe wavelength, atomic absorption measure-

~ ~~~

Table 2 Heating programmes for the determination of Cd, Co, Fe, Ni and Pb in the different constituent parts of cigarettes and in NIST SRMs using platform tube and tube-in-tube atomizers. NIST SRM 57 1 Orchard Leaves, 1573 Tomato Leaves and 1575 Pine Needles were analysed under the heating conditions used for the tobacco samples. NIST SRM 1633a Trace Metals in Coal Fly Ash was analysed under the heating conditions used for the cigarette ash samples

Charring* Atomize?

Matrix Element Tobaco Cd

c o Fe Ni Pb

Paper Cd c o Fe Ni Pb

Filter Cd c o Fe Ni Pb

Ash Cd c o Fe Ni Pb

Smoke Cd c o Fe Ni Pb

TemperaturePC 300

1200 1100 1100 900 500

1500 1200 1300 600 400

1100 1100 1300 600 800

1100 1200 1500 700 400

1100 1100 1100 900

Ramp setting 15 15 15 15 15 10

5 5

10 10 10 15 15 15 10 5 5 5 5 5 5 5 5 5 5

Hold time/s 10 20 10 10 20 10 15 15 25 10 10 20 20 25 10 10 15 10 15 15 10 10 10 10 10

Temperature/"C 1900 2400 2600 2500 1900 2000 2650 2300 2500 1800 1800 2600 2600 2500 2000 1600 2400 2100 2600 2300 2100 2500 2500 2 500 2500

Hold time/s 5 5 4 5 5 4 6 5 5 4 4 5 5 5 4 5 5 5 5 5

5 5 5 5 5

*Drying and pre-charring steps, common to all elements and all matrices, were carried out under the following conditions of temperature

?Maximum heating power and gas-stop conditions were used during atomization. ("C), ramp setting and hold time (s), respectively for drying, 90, 5 and ;!O and pre-charring, 200, 5 and 10.

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JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY, MARCH 1993, VOL. 8 257

ments were performed using the manufacturer's recom- mended wavelengths, slits and lamp currents.22 Owing to the relatively high concentration of Fe in the cigarettes analysed, when this element was determined at its reso- nance wavelength, in the sample solutions obtained as described under Analytical Procedure, the atomic absorp- tion signals produced were well above the linear dynamic range of Fe. Therefore, to avoid excessive dilutions of the sample solutions, which could preclude the determination of some of the other elements found at lower concentra- tions, the less sensitive line at 373.7 nm was selected for the determination of Fe.

The graphite furnace heating conditions (temperature, heating ramp and hold time) were optimized with a view to obtaining maximum integrated absorbance signals for the elements of interest, in each constituent part of the cigarettes. The drying conditions, with a temperature of 90 "C, a ramp setting of 5 and hold time of 20 s, were common to all elements and all matrices. A pre-charring step was found to be needed for better control of the smoke produced on heating the sample solutions at temperatures above the drying temperature, particularly for the tobacco and filter samples. This pre-charring step, also common to all elements and matrices, was carried out at a temperature of 200 "C, a ramp setting of 5 and a hold time of 10 s. The different matrices of the constituent parts of the cigarettes led to different sets of optimum charring and atomization conditions, which are shown in Table 2.

The data in Table 2 show charring temperatures for Co and Pb in tobacco and ash, for Cd, Co, Fe and Ni in wrapping paper, for Pb and Ni in filters, for Cd, Fe, Ni and Pb in ash and for Pb in the nitric acid smoke-treated solutions, which are higher than those normally recom- mended for these elements in the absence of a chemical modifier. The thermal stabilization effect observed for the metals listed above was not studied. However, nitric acid, at the concentrations used for the microwave sample treatments described here, could have a stabilizing effect on

Cd and Pb.24-26 Stabilization of the other elements listed above could also be due to the presence of nitric acid which could convert the metal halides (probably chlorides) into the more stable oxides andor to an effect of the sample matrix on those metals in particular. Detection limits, defined as that concentration of analyte in aqueous solution which corresponds to three standard deviation values of ten consecutive measurements of the blank, repeatability, expressed as relative standard deviation (RSD), and the linear working range for the elements studied are given in Table 3.

Aqueous Standards Versus Standard Additions Appreciable differences between the slopes of the graphs obtained using aqueous standards and the method of standard additions were found for each element in tobacco, paper, filter and ash. Therefore, the standard additions method was used. For the analyses of smoke samples, the smoke produced during the smoking process was forced to pass through the nitric acid solution at the bottom of the smoking unit. The acid solution was then diluted to volume and analysed using aqueous standard calibration graphs as matrix effects were not present in these particular determi- nations.

Accuracy of the Results The accuracy of the measurements for tobacco and ash samples was checked by comparison with certified values of appropriate SRMs. For the filter and wrapping paper analyses, such comparisons were not possible because no appropriate reference materials were available. Therefore, recovery studies were undertaken to assess the accuracy of these measurements. To do this, paper and filter solution aliquots whose Cd, Co, Fe, Ni and Pb concentrations had been already determined were spiked with known amounts of each analyte. Table 4 gives the results obtained. Very small absorbance signals were obtained for the determination of

Table 3 Detection limits as three times the standard deviation of blank measurements, repeatability as relative standard deviation (RSD) and linear working range for Cd, Co, Fe, Ni and Pb in aqueous solutions. Injection volume, 10 pl; number of replicate measurements, 10

Element Detection limitlpg ml-1 RSD(%) Linear working rangelpg ml-1 Cd 3.8 x 0.66 co 8.03 x 10-4 1.28 Fe 5.04 x 1.19 Ni 9.64 x 10-4 0.99 Pb 5.34 x 10-4 0.80

0-0.02 0-0.2 0-1 5 0-0.8 0-0.25

Table 4 Determination of Cd, Co, Fe, Ni and Pb in NIST SRM samples and percentage recovery in filter and wrapping paper samples. Metal concentrations are expressed in pg g-l k standard deviation, except for the Fe content in SRM 1633a, which is expressed as g per 100 g; certified values are given in parentheses and spike levels in brackets. Number of replicate measurements: ten for the NIST SRMs; and five for the recovery studies

Recovery (l3 Per 100 g) NIST SRM

Element 1571 1573 1575 1633a Filter Paper Cd 0.1 1 kO.01

c o 0.19 k 0.01

Fe 299k 1 1

(0.1 1)

(0.2)

(300)

(1.3)

(45)

Ni 1.30k0.05

Pb 46.1 k 0.9

2.9 1 f 0.09 (3)

0.58 k 0.02 (0.6)

686 k 7 (690)

1.58 k 0.04 (-*I

5.99 k 0.20 (6.3)

0.35 k 0.02 ( t 0 . 5 )

0.12 k 0.02 (0.1)

212+ 1 1 (200)

3.39 k 0.05 (3.5)

10.7k0.6 (10.8)

0.95 k 0.07 (1 .O)

(46) 9.37 k0.03

(9.4) 117k9

(1 27) 72.9 k 0.8

(72.4)

45.9 k 0.6

98.7 k 5.3 [2 x 10-31 99.3 k 7.2

[2 x 10-31 95.9 k 2.8

w.41 103.2k5.1

95.3 k 2.8 [8 x lo-']

[2 x 10-7

93.7 f 4 . 5 [2 x 10-31 10 1.5 f 4.8 [2 x 10-31

[0.21 97.6 * 3.8

[4 x 10-21 98.7 k 4.8 [8 x

98.4 .+ 5.3

*No certified value in the SRM.

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Table 5 Concentration ranges (pg g-I) of Cd, Co, Fe, Ni and Pb found in constituent parts of Venezuelan cigarettes. Mean values, in parentheses, are the results of three independent measurements. T= tobacco; P = paper; F=unused filter; F= used filter; A = ash; N.D. =not detectable

Sample Part A T

P

F

F

A

B T

P

F

F

A

C T

P

F

F

A

D T

P

F

F

A

Cd

(2.06) 0.043-0.899

(0.663) 0.089-0.675

(0.240) 0.09 2-0.5 4 3

(0.245)

(7.79)

1.77-2.43

6.81-8.35

1.67-3.04

0.039-0.325

0.086-0.566

(2.04)

(0.132)

(0.3 70)

(0.302)

(7.96)

(2.44)

(0.144)

(0.391)

(0.395)

(8.62)

(1.97)

(0.109)

(0.2 I 1) 0.1 15-0.428

(0.2 17) 6.79-1 1.5

(10.2)

0.101-0.432

6.69-1 1.7

2.07-3.70

0.038-0.295

0.158-0.984

0.148-0.754

7.63-14.3

1.74-2.39

0.034-0.270

0.137-0.433

c o 0.138-0.689

(0.4 30) 0.1 15-0.543

(0.300) 0.010-0.123

(0.052) 0.024-0.109

(0.05 1) 0.8 5-3.43

(1.93)

(0.344) N.D.

0.196-1.07

0.0 14-0.1 32

0.035-0.07 1

9.79-3.46

(0.043)

(0.05 3)

(2.05)

(0.232) N.D.

0.197-0.430

0.158-0.984 (0.391)

0.0 16-0.063 (0.03 3)

1 .OO-4.00 (2.02)

(0.280) N.D.

0.169-0.364

0.008-0.065

0.027-0.044

0.069-3.46

(0.025)

(0.03 3)

(1.49)

Fe 305-580

(443) 58.3-183

(1 15) 12.3-30.5

(20.4) 10.7-28.3

(21.5) 1224-238 1

(1 796)

(338) 13.3-175

(72.7) 19.5-30.1

(24.8)

(26.3)

(1 365) 243-377

(466) 54.3-1 58

(84.0) 10.8-24.9

(1 7.8) 1 1.2-25.7

(19.1) 1268-2323

(1941)

264-454

19.7-29.8

1108-1965

279-677 (443)

8 1.2-1 33 ( 100)

17.3-30.1 (24.3)

2.25-8.75 (5.07)

(1 896) 1353-2941

Ni

(3.90)

(5.00)

(6.06)

(6.15)

(1 7.3)

(4.36)

(2.76)

(4.22)

(4.40)

(1 7.2)

(6.19)

(4.67)

(4.98)

(5.07)

(23.5) 3.10-6.00

(4.59) 2.0 1-6.40

(3.83) 3.78-5.09

(4.33) 3.98-6.02

(4.52)

(1 7.5)

1.20-9.01

3.08-7.18

3.2 1-9.66

3.12-9.80

10.3-26.8

1.18-8.34

1.10-6.49

2.06-8.3 1

2.17-7.25

4.54-3 1.4

2.03-9.65

2.79-8.02

2.83-9.90

2.25-8.75

9.2 3-40.4

1 0.0-2 7.2

Pb

(6.66)

(2.09)

(8.52)

(8.75)

(24.9)

(6.48)

(1.57)

(9.29) 4 .OO- 1 2.1

( 10.0) 17.3-35.5

(24.3) 4.0 1-1 3. I

(7.72) 0.9 1-2.80

(1.71) 3.10-1 2.0

(7.44) 3.24-12.5

(8.03) 15.3-63.6

(31.2)

( 12.4)

(1.32)

(2.95)

(3.03)

(55.1)

3.70-14.6

1.15-3.75

5.55-13.2

4.95-12.1

8.01-52.8

4.69-8.52

0.88-4.06

3.57-1 5.9

9.02- 19.1

0.8 1-2.15

1.27-7.03

2.0 1-5.07

38.0-80.2

the elements of interest in the smoke-treated nitric acid solutions. These absorbance signals were indistinguishable from those obtained when blank solutions, i.e., nitric acid solutions of the same concentration but not treated with smoke, were analysed. Different acid concentrations, solu- tion volumes and increased amounts of smoke were assayed, rendering similar results. There are two possible reasons for these results: either there were no metals in the smoke or the nitric acid solution was not an efficient metal trapper. The first possibility seems to be the most plausible, as it agreeswith the results obtained in the analyses of unused and used cigarette filter samples. For these particular analyses, it was not possible to observe any difference between the two sets of results as evidenced in Table 4 and confirmed by a Student’s f- test. According to these results, smoke is not a means of transporting the metals contained in the tobacco and wrapping paper of cigarettes. The absorbance readings obtained from the nitric acid solution in the smoking unit must then be due to the presence of metalsas impurities in the acid used.

Distribution of Cd, Co, Fe, Ni and Pb in Cigarettes The results in Table 5 show that different constituents of cigarettes contain different concentrations of the elements

of interest. Iron is found at the highest concentration in every part of the cigarettes, followed in decreasing order by :Pb, Ni, Cd and Co. This trend has also been observed in constituent parts of foreign ~ i g a r e t t e s . ~ J ~ J ~ * ~ ~ J ~

Hence it could be possible that trace metals in cigarettes come from similar sources; possible sources such as the itobacco plant and the manufacturing process have to be considered. Among the different cigarette brands selected for this study, there is not a specific one that could be said to contain all the analytes at the highest concentration. Brand A contains intermediate concentrations of all the metals analysed, whereas brand B shows the highest Co concentra- tion; brand C has the highest content of Ni and Fe and brand ID exhibits the highest Pb and Cd content. It is evident from the values in Table 5 that the metals determined in the constituent parts of the different cigarette brands cover a wide range of concentrations. Similar variability was found by Murty ef aI.,15 especially for Cd and Pb. The tobacco, paper and filter materials of the different cigarettes could have different origins, be from different types of soils or have been stored under different conditions and processed in different ways. Hence, it is possible that the variability in metal concentrations could be due to a non-uniform distribution and a variable content of the metals analysed in the tobacco, paper and filters selected for the study.

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The similarity between the results obtained after analysis of the filters (before and after smoking) suggests that the trace metals analysed are either poorly transferred or not transferred from the wrapping paper and the tobacco to the filter during smoking. Most of the trace elements are found in higher concentration in the tobacco. After smoking, most of the metals were contained in the ash. Similar results were found by 1skander.lO This could indicate that the trace elements of interest do not exist as volatile compounds in the paper or tobacco of the cigarettes analysed. This, in turn, rules out the possibility that Cd and Pb, if present in the filter, paper or tobacco of cigarettes, can be inhaled during smoking. The results also rule out the possibility that Cd, Co, Fe, Ni and Pb contained in cigarettes form volatile compounds during smoking. Accordingly, it is valid to infer that the presence of Cd, Co, Fe, Ni and Pb at the concentration levels found in the cigarettes analysed consti- tutes an insignificant health risk to smokers when compared with those posed by nicotine, tar and other organic comDounds found in cigarettes.

References Underwood, E. J., Trace Elements in Human and Animal Nutrition, Academic Press, London, 4th edn., 1977. Rennert, 0. M., and Chan, W. Y., Metabolism of Trace Metals in Man, CRC Press, Boca Raton, FL, 1984. The Merck Index, ed. Windholz, M., Merck, Rahway, NJ, 1976. Iskander, F. Y., Bauer, T. L., and Klein, D. E., Analyst, 1986, 111, 107. Houlgate, P. R., Dhingra, K. S., Nash, S. J., and Evans, W. H., Analyst, 1989, 114, 355. Wynder, E. L., and Hoffman, D., Tobacco and Tobacco Smoke, Academic Press, New York, 1967. Wagner, G. H., and Yeargan, R., Plant Physiol., 1986,182,274. Iskander, F. Y., J. Radioanal. Nucl. Chem., 1985, 91, 191.

9 Iskander, F. Y., J. Radioanal. Nucl. Chem., 1986, 97, 107. 10 Iskander, F. Y., J. Radioanal. Nucl. Chem., 1985, 89, 51 1. 1 1 Hallak, A. B., J. Radioanal. Chem., 1981, 67, 459. 12 Pung, T. C., Chou, C. C., Tsai, H. T., and Wu, S. C., J.

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40, 1998. 15 Murty, K. S. N., Tjell, J. C., and Gopalachari, N. C., Plant Soil,

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24 Feitsma, K. G., Franke, J. P., and de Zeeuw, R. A., Analyst, 1984, 109, 789.

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Paper 2/03522G Received July 6, 1992

Accepted October 19, 1992

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