Elemental analysis of Akçaabat tobacco and its ash by EDXRF spectrometry

Journal of Quantitative Spectroscopy & Radiative Transfer 78 (2003) 409 – 415

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Elemental analysis of Ak,caabat tobacco and its ash by EDXRF spectrometry U. C,evika , E. Ergenb , G. Budakc;∗ , A. Karabulutc , E. Tira,so9glua , G. Apaydina , A.I. Kopyaa a

Department of Physics, Faculty of Arts and Sciences, Karadeniz Technical University, Trabzon, Turkey b Department of Urology, Faculty of Medicine, Atat!urk University, Erzurum, Turkey c Department of Physics, Faculty of Arts and Sciences, Atat!urk University, Erzurum 25240, Turkey Received 20 June 2002; accepted 1 October 2002

Abstract The concentration of eight di=erent elements in tobacco of di=erent region in Ak,caabat (Trabzon/Turkey) was determined using energy dispersive X-ray @uorescence method. A radioisotope excited X-ray @uorescence analysis using the method of multiple standard addition is applied for the elemental analysis of tobacco and its ash. An annular 50 mCi241 Am radioactive source and an annular 50 mCi55 Fe radioactive source were used for excitation of characteristic K X-rays. An Si(Li) detector which has a 147 eV full width at half maximum for 5:9 keV photons was used for intensity measurements. A qualitative analysis of spectral peaks showed that the samples contained potassium, calcium, titanium, iron, copper, bromine, strontium and barium. Evaluation of these elements with their potential hazards for smokers is brie@y discussed. ? 2003 Published by Elsevier Science Ltd. Keywords: Energy dispersive X-ray @uorescence; Tobacco and its ash; The method of multiple standard addition; Elemental analysis; Trace element analysis

1. Introduction Trace elements have important ejects in the life processes. Some of these elements are toxic for the humans even at a very low level of intake. There has been considerable e=ort to determine the concentrations of trace elements in food and plant leaves. Tobacco leaves are widely used for manufacturing smoking materials and the trace element concentrations in the plant as well as in the cigarette tobacco have been determined in several countries by various techniques [1–10]. ∗

Corresponding author. Fax: +90-422-233-1062. E-mail address: [email protected] (G. Budak).

0022-4073/03/$ - see front matter ? 2003 Published by Elsevier Science Ltd. PII: S 0 0 2 2 - 4 0 7 3 ( 0 2 ) 0 0 2 6 3 - 7

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Several carcinogens have been identiLed in tobacco as gaseous and particulate-phase of tobacco smoke. We have seen that mortality rate of diseases caused by smoking is more 350 000 per year in United States of America and so it shows us that it is a common public health problem [11]. Several some metals can cause cancer [10,12]. We have seen increase in prevalence of malign diseases especially in human respiratory system (bronchial cancer, etc.) and urinary system (urothelial cancer). Cigarette smoking is responsible for approximately 90% of lung cancers. More than 4000 individual chemical constituents of cigarette smoke have identiLed. Unadulterated tobacco contributes 2550 of these with the remainder representing additives, pesticides and other organic and metallic compounds [11,13,14]. Radioactive constituents are present in both tobacco and tobacco smoke. They include radon and it’s decay products. These radioisotopes may contribute to the carcinogenecity of cigarette smoke [11,13]. It is known that some metals can cause cancer [12]. Also it is known that some enzymes, which control the chemical changes in tissue cells, are metalloenzymes. Studies indicate that there is a deLnite correlation between the level of trace elements in the human body and some diseases [15]. Several investigators [16–20] have shown that Sb, Br, As, Cd and Co (as cobalt carbonyl) are toxic for the human bio system even at very low levels of intake. Most of these toxic elements are present in tobacco leaves and food due to increasing industrialization and pollution, uptake from soil and fertilizer, pesticides, storage, processing, packing and other domestic activities. With the use of some pesticides, plants may incorporate in their structure a certain amount of toxic elements. Due to a large consumption of tobacco in Turkey, a study of heavy metals and rare earth elements in tobacco products is desirable. Therefore, it is necessary to measure these trace elements in tobacco for assessing the possible role they may play to cause some diseases. In this work, tobacco and its ash are analysed quantitatively for its potassium, calcium, titanium, iron, copper, bromine, strontium and barium contents. 2. Experimental 2.1. Method Quantitative determination of elements is an important task in industrial, chemical, environmental, mineralogical, physical, medical and other Lelds. Among the methods of elemental analysis are atomic absorption spectrometry, neutron activation analysis and X-ray @uorescence (XRF). XRF techniques can be divided into two, namely, the wavelength method and the energy dispersive method. Energy dispersive X-ray @uorescence (EDXRF) o=ers several unique advantages over other analytical methods [21]. It allows simultaneous detection and determination of several elements, it is sensitive and reproducible. Sample preparation is usually simple and fast. Also, the equipment cost is much cheaper than the conventional wavelength X-ray @uorescence techniques, especially if a radioisotope is used instead of an X-ray tube for excitation. The EDXRF method gives also a possibility of trace analysis of biological and geological samples. In recent years, EDXRF method has been used for elemental analysis by several authors [22–29]. The method involves the addition of known quantities of the analyte to the specimen. If analyte is presented at low levels and no suitable standards are available, standard addition may prove to be an alternative, especially if the analyst is interested in only one analyte element. The principle is the following: Adding a known amount of analyte i(QWi ) to the unknown sample gives an increased

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411

Fig. 1. Geometry of experimental setup.

intensity Ii + QIi . Assuming a linear calibration, the following equations apply: I i = M i Wi :

(1)

For the original samples and Ii + QIi = Mi (Wi + QWi )

(2)

for the sample with the addition. Thus, the method assumes that linear calibration is adequate throughout the range of addition because it assumes that an increase in the concentration of analyte by amount QWi will increase the intensity by Mi QWi . These equations can be solved for the weight fraction of element i (Wi ). To check the linearity of the calibration, the process can be repeated by adding di=erent amounts of the analyte to the sample and plotting the intensity measured versus the concentrations added. The intercept of the line on the concentration axis equals Wi . The intensities used for calibration must be corrected for background and line overlap [21]. 2.2. Sample preparation Tobacco samples were collected from Ak,caabat town of Trabzon, located at latitude 41◦ north and longitude 39◦ 5 east. Samples investigated in this work were prepared from tobacco and its ash. These samples were dried in a Heraeus furnace and then ground in a Spex mill. To reduce particle size e=ects, the powder obtained were sieved using a 400 mesh sieve and then mixed during 20 min. One hundred milligrams of this powder was spread homogeneously on a mylar Llm stretched across a Lbre frame. 2.3. Excitation and spectral analysis Samples positioned according to the geometry of Fig. 1 were irradiated by 59:5 keV photons emitted by an annular 50 mCi241 Am annular radioactive source for iron, copper, bromine, strontium,

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Characteristic X-rays

Beryllium Window

TENNELEC 950 High Voltage 0.6 kV

Si(Li) PGT PO14B Preamplifier

Liquid nitrogen PCA+ADC Analyzer 2048 Channel

TENNELEC TC244 Linear Amplifier Oscilloscope

Fig. 2. Block diagram of the counting system.

10000

KK α

8000

Ca Kα

Counts

6000

MnK α

4000

CaK β 2000

MnK β

TiK α 0 400

600

800

1000

1200

1400

1600

1800

2000

Channel

Fig. 3. A typical spectrum for elements excited by

55

Fe radioactive source.

and barium determination and irradiated by 5:9 keV photons emitted by an annular 50 mCi 55 Fe radioactive source for potassium, calcium and titanium. The block diagram of the counting system is shown in Fig. 2. To detect the radiation scattered from a sample, a PGT Si(Li) detector having 147 eV full width at half maximum (FWHM) for 5:9 keV photons was used. Two thousand and forty-eight channels of a multichannel analyser were employed in data acquisition. In qualitative analysis, characteristic X-rays emitted by excited atoms of the sample were registered for time intervals of 1000 and 2000 s. Qualitative analysis of spectral peaks showed that the samples contained potassium, calcium, titanium, iron, copper, bromine, strontium and barium. A representative example of a spectrum is given in Fig. 3 for elements excited by the 241 Am radioactive source and in Fig. 4 for elements excited by the 55 Fe radioactive source.

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413

1000

Counts

FeK α

500

CuK α

BrK α SrK α

BaK α

0 500

1000

1500

2000

Channel

Fig. 4. A typical spectrum for elements excited by

241

Am radioactive source.

Table 1 Addition standards for potassium, calcium, titanium, iron, copper, bromine, strontium and barium and their purities Analyte

Addition standard

Purity (%)

Percent analyte

K Ca Ti Fe Cu Br Sr Ba

KBr CaCO3 TiO2 Fe Cu2 O KBr SrCO3 BaCO3

99.5 99 99 99 97 99.5 98 99.9

33 40 60 100 89 67 59 70

Quantitative analysis for these elements was carried out using the method of multiple standard additions. In this method, certain amounts of the element to be analysed, called analyte, are added to samples. The chemicals containing these addition standards as well as their purities are given in Table 1. 3. Results and discussion The concentration of eight elements in tobacco alters before and after smoking and ash are shown in Table 2. K and Ca concentrations were always higher in the tobacco and its ash. A partial X-ray spectrum of the ash sample for the popular brand obtained after irradiation is shown in Figs. 3–4 which identiLes some of the X-ray peaks for some elements shown in Table 2. Toxic elements such

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Table 2 Potassium, calcium, titanium, iron, copper, bromine, strontium and barium concentration for tobacco and its ash Element

K Ca Ti Fe Cu Br Sr Ba

Concentration (%) Tobacco

Ash

11.8 2.99 0.005 0.156 0.051 0.028 0.007 0.009

28.2 9.27 0.048 0.211 0.075 0.030 0.030 0.025

as Br, Co and Sb are of great importance in toxicological studies, as these elements are partly or completely volatized in the smoke and are inhaled or absorbed through smoking tobacco and its ash were analysed by EDXRF and concentrations of potassium, calcium, titanium, iron, copper, bromine, strontium and barium were determined. The values of the concentrations of elements are given in Table 2. In elemental analysis using X-ray @uorescence technique, matrix e=ects are known to distort the linearity of “photo peak area versus concentration” graphs for analyses [4]. To minimize or to eliminate matrix e=ects we proceeded as follows: (i) The K net peak areas for iron, copper, bromine, strontium and barium obtained from sample spectra were normalized by dividing them by Compton net peak areas. The K net peak areas for potassium, calcium and titanium obtained from sample spectra were normalized by dividing them by MnK  peak areas. (ii) To obtain an ideal grain size for the samples the ground material was sieved using a 400-mesh sieve. In our measurements maximum relative errors due to the counting system were of the order ∼ 0:5– 5%. Errors originating from sample weighing, source intensity and system geometry were about 4%. The combined relative error in our results was accordingly of the order of 8%. EDXRF technique is fast, economical and fully suitable for simultaneous quantitative determinations of many matrix elements. Therefore, it presents some advantage over other spectrometric methods. The total typical time for EDXRF is much less than for a conventional chemical analysis [27]. References [1] Mishra UC, Shaikh GN. Determination of trace element concentrations of Indian cigarette tobacco by instrumental neutron activation analysis. J Radioanal Nucl Chem 1981;78:285–90. [2] Guelovali MC. Trace elements in Turkish tobacco determined by instrumental neutron activation analysis. J Radioanal Nucl Chem 1983;78:189–98.

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