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The Science of the Total Environment 145 (1994) 157-161
Microemulsion determination of lead and cadmium in Saudi Arabian petroleum products by inductively coupled plasma mass spectrometry (ICP/MS) H.M. A1-Swaidan Department of Chemistry, King Saud University College of Science, P.O. Box 2455, Rivadh 11451. Saudi Arabia
(Received 28 November 1992:accepted 15 December 1993)
Abstract The concentrations of lead and cadmium were determined in Saudi Arabian petroleum products by inductively coupled plasma mass spectrometry (ICP/MS). A microemulsion procedure was used for sample pretreatments while the standard addition method was used for sample analysis. Detection limits were 0.006-0.160 #g/g lead and 0.015-0.170 tzg/g cadmium in petroleum product samples. Recoveries of added lead and cadmium as oil soluble salts were made and found to be in the 99-103% and 100-101% ranges, respectively. The mean lead and cadmium levels in aviation turbine oil were 0.16 and 0.17 #g/g, and in diesel fuel oil were 0.35 and 0.01 /~g/g, respectively whereas in leaded motor gasoline, the concentrations were 901.00 and 0.085 #g/g, respectively. The percentage relative standard deviations for five replicate samples were < 5% in all cases. The results are discussed in relation to the sources of the metals, and the possible environmental impact and health risks. Key words." Lead; Cadmium; Microemulsion; Petroleum products; Inductively coupled plasma mass spectrometry
(ICP/MS)
I. Introduction Lead and cadmium are well known environmental pollutants and have been widely studied in recent years. There are two very important reasons for studying lead emission into the atmosphere. Firstly, inhaled lead may pass via the respiratory system into the blood stream and hence contribute to lead exposure of humans. Secondly, airborne lead is progressively removed from the atmosphere by wet and dry deposition processes causing contamination of other environmental media [1].
The US Environmental Protection Agency has examined the emission of lead into the atmosphere. The greatest source of lead emission was from vehicles burning leaded petrol although the relative importance of this source in the US and some other countries may have been reduced in recent years due to the progressive introduction of unleaded fuel [2]. Even at rather low concentrations, cadmium can produce irreversible adverse effects in the human body by its accumulation in kidneys, liver, or via the food chain for occupationally non-exposed
0048-9697/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved. SSDI 0048-9697(93)03667-Q
158
persons [3,4]. Combustion of fuels provides the most important source of cadmium pollution [5]. Inductively coupled plasma mass spectrometry (ICP/MS) is an effective technique for the determination of lead and cadmium in petroleum products. It has emerged as a promising and versatile means of providing rapid, multielement capability and high sensitivity for a wide variety of samples [6,71. Several sampling methods have been used for determining lead and cadmium levels in oil products [8,9]. The common analytical procedure includes direct aspiration of the sample after dilution with an appropriate solvent, and dry and wet ashing. Direct oil sample injection methods cause instrumental problems whereas the first method is time consuming with possible loss of some of the volatile elements [10,11]. Determination of trace metals in crude oil by ICP/MS with microemulsion sample introduction has been reported [121. This study includes determination of lead and cadmium in Saudi Arabian petroleum product samples such as aviation turbine oil, motor gasoline and diesel fuel. The previously investigated microemulsion method for determination of trace metals in crude oil has been used for sample pretreatments[12].
2. Experimental Lead and cadmium contents were determined using a Sciex Elan ICP/MS instrument, with a standard addition program supplied by Sciex for determination of concentration, standard deviation, and recovery values for both elements [13]. A Sciex Elan model 250 was used with a 15BCO12Bcomputer by Matrox Electronic System Ltd., an Epson printer model LQI050 and a Gilson Minipuls 2 peristaltic pump. An Edmund Bfihler vortex mixer, model 25, was used for crude oil sample agitation [13]. Operating conditions and experimental parameters are shown in Table 1.
2.1. Reagents Chemicals of analytical reagent grade were used without further purification, including lead and cadmium cyclohexane butyrate (Eastman Organic Chemicals, Rochester, NY), indium oxide (Spex
H.M. AI-Swaidan / Sci. Total Environ. 145 (1994) 157-161
Table 1 Operating conditions of Elan ICP/MS Parameter
Value
Reference incident power (kw) Plasma gas flow (1/min) Auxiliary gas flow (l/min) Nebulizer gas pressure (p.s.i.) Measurements per peak Repeats per integration Sample flow (ml/min) Resolution Counting precision Threshold Measurements time (s)
1.2 13 1.4 40 5 5 1.0 Low 0.1 l 0.05
Industries Inc., NJ), and analar nitric acid (sp.gr. 1.42, 69-71%, BDH Chemicals Ltd., Poole, UK). Tetralin (l,2,3,4-tetrahydronaphthalene; Fluka AG, Buchs SG, Switzerland) was used as a cosolvent. A nonionic surfactant, Triton X-100 (BDH Chemicals Ltd., Poole, UK) was chosen as the emulsifying agent. Deionized distilled water was obtained using a Corning Mega-pure water distillation apparatus model MP3. A nitric acid solution 40% (v/v) was prepared by the dilution of concentrated nitric acid with distilled deionized water. Stock solutions (100 ppm) of lead and cadmium were prepared by dissolving the weighed organo-metallic salts in a nitric acid solution 40% (v/v). Solutions of multi-element standards of lead (25 ppm) and cadmium (10 ppm) were prepared by dilution from the stock solutions. An indium stock solution (100 ppm) was prepared by dissolving its weighed salt into 1% (v/v) nitric acid solution.
2.2. Samples Saudi Arabian petroleum product samples including aviation turbine oil, motor gasoline, and diesel fuel oil were supplied by Petromin Oil Company, Saudi Arabia. Some general properties of these samples are shown in Table 2. 2.3. Procedure A 0.5-g aliquot ofoil product sample was weigh-
159
H.M. AI-Swaidan / Sci. Total Environ. 145 (1994) 157-161 Table 2 General properties of petroleum product samples Test
Gravity, API at 60°F Sulfur total, wt% Viscosity Acidity total of mg KOH/g Description
Oil product sample Aviation turbine
Motor gasoline
Diesel fuel
47.12 0.71 Kinematic at 20°C, 2.68 0.0035 Bright and Clear
57.0 22.0 (ppm) --Red and Sweet
39.3 < 0.02 at 37.8°C, SUS, 36.0 0.006
ed into a stoppered 200-ml glass bottle. An equivalent weight of tetralin was then added to each bottle followed by 0-1.0 ml of the multielernent standard solution (containing 25 ppm Pb and l0 ppm Cd) and the contents mixed until a homogenous solution was obtained. Each sample then received a 10-g portion of triton X-100, 0.5 ml of indium solution (100 ppm) and the mixture mechanically agitated until a homogenous solution phase was produced. Deionized water was added gradually with continual agitation until a final volume of 50.0 ml was reached. Intensities for Pb and Cd in blank solutions (prepared in the same way as the sample) as well as in different sample solutions were measured by ICP/MS using the standard addition method. Five sample replicates were made and measured to determine recoveries and standard deviations. Microemulsion ICP/MS is an effective technique for the analysis of trace metals in petroleum products; it is less time consuming than other techniques and there is a reduction of trace elements lost by evaporation during dry and wet ashing techniques. Successive samples were spiked with standard organo-metallic salt solutions of both lead and cadmium to counteract the variation of different sample and standard matrices. Blank results were then subtracted from both samples and standards. This was accomplished using the standard addition method. Indium (l ppm) was added as an internal standard to correct any possible signal variations [12]. Five replicates of aviation turbine sample having 0.160 #g/g lead and 0.170 #g/g cadmium gave a standard deviation of ±0.002 (±1.27%) and
± 0.005 ( ± 3.03%), respectively for the precision of assay. The accuracy of the results for this method was determined by comparing with the solvent extraction method [9]. An aviation turbine sample with higher cadmium content (0.0170/~g/g) gave 0.186 /~g/g by the solvent extraction method. The detection limits are defined as the concentration required to give a signal equal to three times the standard deviation obtained. The limits are 0.006-0.160 #g Pb/g and 0.015-0.170 #g Cd/g in aviation turbine oil samples. 3. Results and discussion
The concentration of total lead and cadmium, standard deviation and relative standard deviations were determined in the oil product samples and the results are presented in Table 3. Gasoline
Table 3 Concentrations of lead and cadmium in petroleum product samples Oil Sample
Metal
Concentration (#g/g, mean + S.D. a)
%R.S.D. a
Aviation turbine Gasoline motor Diesel fuel
Pb Cd Pb Cd Pb Cd
0.160 0.170 901.000 0.085 0.350 0.010
1.27 3.03 2.11 4.88 2.86 3.10
+ 4+ + ± +
0.002 0.005 19.011 0.004 0.010 0.0003
aS.D. and %R.S.D. are standard deviation and % relative standard deviation for five replicates, respectively.
160
H.M. Al-Swaidan/Sci. Total Environ. 145 (1994) 157-161
Table 4 Recoveries for lead and cadmium in petroleum product samples Oil Sample
Aviation turbine Gasoline motor Diesel fuel
Metal
Pb Cd Pb Cd Pb Cd
Correlation coefficient
Recovery Added (p.g/g)
Found (#g/g)
% Recovery
1.000 1.000 1000.000 1.000 1.000 1.000
1.022 1.005 992.000 1.008 1.016 1.003
102.2 100.5 99.2 100.8 101.6 100.3
motor oil showed exceptionally high levels of lead concentration (901 /~g/g). Lead is added to gasoline as an anti-knock agent in the form of organic tetraalkyl lead. The concentration of lead in gasoline motor oil is higher than permitted international values. The concentrations of lead in aviation turbine and diesel fuel are 0.16 #g/g and 0.35 #g/g, respectively. These are lower as there are no lead additives in aviation turbine and diesel fuel oil. In Britain, the maximum permitted lead content of petroleum is 0.04 g/dm 3, whilst in Germany it is 0.15 g/dm 3. In the US, the situation is different due to the sale of unleaded gasoline necessary for the cars fitted with catalytic exhaust emission systems [1]. The cadmium content of various petroleumproduct samples is listed in Table 3. Diesel fuel has extremely low cadmium contents (0.01 /~g/g). In gasoline fuel, the cadmium value is somewhat higher (0.085/zg/g), while the highest values occur in aviation turbine oil with contents around 0.17 /~g/g. In general, the cadmium values found are relatively higher than reported cadmium contents for similar oils [4,14]. The percentage relative standard deviation studies for accuracy and precision using five sample replicates were found to be less than 5% in all cases, as shown in Table 3. Table 4 shows percentage recovery and correlation coefficient data for lead and cadmium in the analyzed oil product samples.
4. Conclusions The microemulsion method demonstrates the superiority of direct determination in comparison
0.999 0.998 0.998 0.999 0.999 0.999
with analytical methods used formerly which required severe precautions against contamination and were time consuming. ICP/MS has proved to be an effective analytical technique for determining lead and cadmium in petroleum products because of its multielement capability, accuracy and low detection limits. The high concentration of cadmium observed could be one of the main causes of cadmium contamination in the Saudi Arabian environment. More studies are needed to reduce cadmium content in Saudi Arabian oil products to within permitted limits.
5. Acknowledgements The author wishes to thank Mr K.O. Ahmed and Mr A.A. AI-Gadi for their assistance and Petromin company for supplying the samples. This research was done with financial support provided by King Saud University.
6. References I R.M. Harrison and D.P.H. Laxen, Lead Pollution Causes and Control, Chapman and Hall, London, 1981. 2 US Environmental Protection Agency, Control Techniques for Lead Air Emissions, EPA-450/2-77-012, 1977. 3 L. Friberg, T. KjeUstr6m, G.T. Nordberg and M. Piscator+ Cadium, In L. Fribert, G.F. Nordberg and V.B. Vouk (Eds.), Handbook on the Toxicology of Metals, Elsevier, Amsterdam, 1979, 355 pp. 4 M. Stoeppler, Cadmium, In E. Merian, M. Geldmachervon Mallinckrodt, G. Machata, H.W. Niirnberg, H.W. Schlipk6ter and W. Stumm (Eds.), Hrsg., Metalle in der Umwelt, VerlagChemie, Weinheim/Bergstr, 1984, 375 pp. 5 I.D. Schladot and H.W. Niirnberg, Atmosph/irische
161
H.M. AI-Swaidan / Sci. Total Environ. 145 (1994) 157-161
6
7
8
9
Belastung durch toxische Metalle in der Bundesrepublik Deutschland, Emission und Deposition, Jiil-Ber, 1982, 1776. R.S. Houk and J.J. Thompson, Inductively coupled plasma mass spectrometry. Mass Spectrom. Rev., 7 (1988) 425. G.M Hieftje and G.H. Vickers, Developments in plasma source/mass spectrometry. Anal. Chim. Acta, 216 (1989) 1. H.D. Narres, C. Mohl and M. Stoeppler, Metal analysis in difficult materials with platform furnace Zeemanatomic absorption spectrometry. Int. J. Environ. Anal. Chem., 18 (1984) 267. H.M. AI-Swaidan, Simultaneous determination of trace metals in Saudi Arabian crude oil products by inductively
10 11 12
13 14
coupled plasma mass spectrometry (1CP/MS). Anal. Lett., 21 (1988) 1487. V. Valkovic, Trace elements in petroleum, Petroleum Publishing, Tulsa, OK, 1978. R.S. Houk, Mass spectrometry of inductively coupled plasmas. Anal. Chem., 56 (1986)97A. C.J. Lord, Determination of trace metals in crude oils by inductively coupled plasma mass spectrometry with microemulsion sample introduction. Anal. Chem, 63 (1991) 1594. ICP/MS Operators Manual, Sciex Elan, 55 Glen Cameron Road, Thurnhill, Ontario, Canada, 1984. DGMK-Berichte, Forschungsbericht 264, Bestimmung von cadmium in Mineral 61 produkten, Hamburg, 1983.
The Science of the Total Environment 145 (1994) 157-161
Microemulsion determination of lead and cadmium in Saudi Arabian petroleum products by inductively coupled plasma mass spectrometry (ICP/MS) H.M. A1-Swaidan Department of Chemistry, King Saud University College of Science, P.O. Box 2455, Rivadh 11451. Saudi Arabia
(Received 28 November 1992:accepted 15 December 1993)
Abstract The concentrations of lead and cadmium were determined in Saudi Arabian petroleum products by inductively coupled plasma mass spectrometry (ICP/MS). A microemulsion procedure was used for sample pretreatments while the standard addition method was used for sample analysis. Detection limits were 0.006-0.160 #g/g lead and 0.015-0.170 tzg/g cadmium in petroleum product samples. Recoveries of added lead and cadmium as oil soluble salts were made and found to be in the 99-103% and 100-101% ranges, respectively. The mean lead and cadmium levels in aviation turbine oil were 0.16 and 0.17 #g/g, and in diesel fuel oil were 0.35 and 0.01 /~g/g, respectively whereas in leaded motor gasoline, the concentrations were 901.00 and 0.085 #g/g, respectively. The percentage relative standard deviations for five replicate samples were < 5% in all cases. The results are discussed in relation to the sources of the metals, and the possible environmental impact and health risks. Key words." Lead; Cadmium; Microemulsion; Petroleum products; Inductively coupled plasma mass spectrometry
(ICP/MS)
I. Introduction Lead and cadmium are well known environmental pollutants and have been widely studied in recent years. There are two very important reasons for studying lead emission into the atmosphere. Firstly, inhaled lead may pass via the respiratory system into the blood stream and hence contribute to lead exposure of humans. Secondly, airborne lead is progressively removed from the atmosphere by wet and dry deposition processes causing contamination of other environmental media [1].
The US Environmental Protection Agency has examined the emission of lead into the atmosphere. The greatest source of lead emission was from vehicles burning leaded petrol although the relative importance of this source in the US and some other countries may have been reduced in recent years due to the progressive introduction of unleaded fuel [2]. Even at rather low concentrations, cadmium can produce irreversible adverse effects in the human body by its accumulation in kidneys, liver, or via the food chain for occupationally non-exposed
0048-9697/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved. SSDI 0048-9697(93)03667-Q
158
persons [3,4]. Combustion of fuels provides the most important source of cadmium pollution [5]. Inductively coupled plasma mass spectrometry (ICP/MS) is an effective technique for the determination of lead and cadmium in petroleum products. It has emerged as a promising and versatile means of providing rapid, multielement capability and high sensitivity for a wide variety of samples [6,71. Several sampling methods have been used for determining lead and cadmium levels in oil products [8,9]. The common analytical procedure includes direct aspiration of the sample after dilution with an appropriate solvent, and dry and wet ashing. Direct oil sample injection methods cause instrumental problems whereas the first method is time consuming with possible loss of some of the volatile elements [10,11]. Determination of trace metals in crude oil by ICP/MS with microemulsion sample introduction has been reported [121. This study includes determination of lead and cadmium in Saudi Arabian petroleum product samples such as aviation turbine oil, motor gasoline and diesel fuel. The previously investigated microemulsion method for determination of trace metals in crude oil has been used for sample pretreatments[12].
2. Experimental Lead and cadmium contents were determined using a Sciex Elan ICP/MS instrument, with a standard addition program supplied by Sciex for determination of concentration, standard deviation, and recovery values for both elements [13]. A Sciex Elan model 250 was used with a 15BCO12Bcomputer by Matrox Electronic System Ltd., an Epson printer model LQI050 and a Gilson Minipuls 2 peristaltic pump. An Edmund Bfihler vortex mixer, model 25, was used for crude oil sample agitation [13]. Operating conditions and experimental parameters are shown in Table 1.
2.1. Reagents Chemicals of analytical reagent grade were used without further purification, including lead and cadmium cyclohexane butyrate (Eastman Organic Chemicals, Rochester, NY), indium oxide (Spex
H.M. AI-Swaidan / Sci. Total Environ. 145 (1994) 157-161
Table 1 Operating conditions of Elan ICP/MS Parameter
Value
Reference incident power (kw) Plasma gas flow (1/min) Auxiliary gas flow (l/min) Nebulizer gas pressure (p.s.i.) Measurements per peak Repeats per integration Sample flow (ml/min) Resolution Counting precision Threshold Measurements time (s)
1.2 13 1.4 40 5 5 1.0 Low 0.1 l 0.05
Industries Inc., NJ), and analar nitric acid (sp.gr. 1.42, 69-71%, BDH Chemicals Ltd., Poole, UK). Tetralin (l,2,3,4-tetrahydronaphthalene; Fluka AG, Buchs SG, Switzerland) was used as a cosolvent. A nonionic surfactant, Triton X-100 (BDH Chemicals Ltd., Poole, UK) was chosen as the emulsifying agent. Deionized distilled water was obtained using a Corning Mega-pure water distillation apparatus model MP3. A nitric acid solution 40% (v/v) was prepared by the dilution of concentrated nitric acid with distilled deionized water. Stock solutions (100 ppm) of lead and cadmium were prepared by dissolving the weighed organo-metallic salts in a nitric acid solution 40% (v/v). Solutions of multi-element standards of lead (25 ppm) and cadmium (10 ppm) were prepared by dilution from the stock solutions. An indium stock solution (100 ppm) was prepared by dissolving its weighed salt into 1% (v/v) nitric acid solution.
2.2. Samples Saudi Arabian petroleum product samples including aviation turbine oil, motor gasoline, and diesel fuel oil were supplied by Petromin Oil Company, Saudi Arabia. Some general properties of these samples are shown in Table 2. 2.3. Procedure A 0.5-g aliquot ofoil product sample was weigh-
159
H.M. AI-Swaidan / Sci. Total Environ. 145 (1994) 157-161 Table 2 General properties of petroleum product samples Test
Gravity, API at 60°F Sulfur total, wt% Viscosity Acidity total of mg KOH/g Description
Oil product sample Aviation turbine
Motor gasoline
Diesel fuel
47.12 0.71 Kinematic at 20°C, 2.68 0.0035 Bright and Clear
57.0 22.0 (ppm) --Red and Sweet
39.3 < 0.02 at 37.8°C, SUS, 36.0 0.006
ed into a stoppered 200-ml glass bottle. An equivalent weight of tetralin was then added to each bottle followed by 0-1.0 ml of the multielernent standard solution (containing 25 ppm Pb and l0 ppm Cd) and the contents mixed until a homogenous solution was obtained. Each sample then received a 10-g portion of triton X-100, 0.5 ml of indium solution (100 ppm) and the mixture mechanically agitated until a homogenous solution phase was produced. Deionized water was added gradually with continual agitation until a final volume of 50.0 ml was reached. Intensities for Pb and Cd in blank solutions (prepared in the same way as the sample) as well as in different sample solutions were measured by ICP/MS using the standard addition method. Five sample replicates were made and measured to determine recoveries and standard deviations. Microemulsion ICP/MS is an effective technique for the analysis of trace metals in petroleum products; it is less time consuming than other techniques and there is a reduction of trace elements lost by evaporation during dry and wet ashing techniques. Successive samples were spiked with standard organo-metallic salt solutions of both lead and cadmium to counteract the variation of different sample and standard matrices. Blank results were then subtracted from both samples and standards. This was accomplished using the standard addition method. Indium (l ppm) was added as an internal standard to correct any possible signal variations [12]. Five replicates of aviation turbine sample having 0.160 #g/g lead and 0.170 #g/g cadmium gave a standard deviation of ±0.002 (±1.27%) and
± 0.005 ( ± 3.03%), respectively for the precision of assay. The accuracy of the results for this method was determined by comparing with the solvent extraction method [9]. An aviation turbine sample with higher cadmium content (0.0170/~g/g) gave 0.186 /~g/g by the solvent extraction method. The detection limits are defined as the concentration required to give a signal equal to three times the standard deviation obtained. The limits are 0.006-0.160 #g Pb/g and 0.015-0.170 #g Cd/g in aviation turbine oil samples. 3. Results and discussion
The concentration of total lead and cadmium, standard deviation and relative standard deviations were determined in the oil product samples and the results are presented in Table 3. Gasoline
Table 3 Concentrations of lead and cadmium in petroleum product samples Oil Sample
Metal
Concentration (#g/g, mean + S.D. a)
%R.S.D. a
Aviation turbine Gasoline motor Diesel fuel
Pb Cd Pb Cd Pb Cd
0.160 0.170 901.000 0.085 0.350 0.010
1.27 3.03 2.11 4.88 2.86 3.10
+ 4+ + ± +
0.002 0.005 19.011 0.004 0.010 0.0003
aS.D. and %R.S.D. are standard deviation and % relative standard deviation for five replicates, respectively.
160
H.M. Al-Swaidan/Sci. Total Environ. 145 (1994) 157-161
Table 4 Recoveries for lead and cadmium in petroleum product samples Oil Sample
Aviation turbine Gasoline motor Diesel fuel
Metal
Pb Cd Pb Cd Pb Cd
Correlation coefficient
Recovery Added (p.g/g)
Found (#g/g)
% Recovery
1.000 1.000 1000.000 1.000 1.000 1.000
1.022 1.005 992.000 1.008 1.016 1.003
102.2 100.5 99.2 100.8 101.6 100.3
motor oil showed exceptionally high levels of lead concentration (901 /~g/g). Lead is added to gasoline as an anti-knock agent in the form of organic tetraalkyl lead. The concentration of lead in gasoline motor oil is higher than permitted international values. The concentrations of lead in aviation turbine and diesel fuel are 0.16 #g/g and 0.35 #g/g, respectively. These are lower as there are no lead additives in aviation turbine and diesel fuel oil. In Britain, the maximum permitted lead content of petroleum is 0.04 g/dm 3, whilst in Germany it is 0.15 g/dm 3. In the US, the situation is different due to the sale of unleaded gasoline necessary for the cars fitted with catalytic exhaust emission systems [1]. The cadmium content of various petroleumproduct samples is listed in Table 3. Diesel fuel has extremely low cadmium contents (0.01 /~g/g). In gasoline fuel, the cadmium value is somewhat higher (0.085/zg/g), while the highest values occur in aviation turbine oil with contents around 0.17 /~g/g. In general, the cadmium values found are relatively higher than reported cadmium contents for similar oils [4,14]. The percentage relative standard deviation studies for accuracy and precision using five sample replicates were found to be less than 5% in all cases, as shown in Table 3. Table 4 shows percentage recovery and correlation coefficient data for lead and cadmium in the analyzed oil product samples.
4. Conclusions The microemulsion method demonstrates the superiority of direct determination in comparison
0.999 0.998 0.998 0.999 0.999 0.999
with analytical methods used formerly which required severe precautions against contamination and were time consuming. ICP/MS has proved to be an effective analytical technique for determining lead and cadmium in petroleum products because of its multielement capability, accuracy and low detection limits. The high concentration of cadmium observed could be one of the main causes of cadmium contamination in the Saudi Arabian environment. More studies are needed to reduce cadmium content in Saudi Arabian oil products to within permitted limits.
5. Acknowledgements The author wishes to thank Mr K.O. Ahmed and Mr A.A. AI-Gadi for their assistance and Petromin company for supplying the samples. This research was done with financial support provided by King Saud University.
6. References I R.M. Harrison and D.P.H. Laxen, Lead Pollution Causes and Control, Chapman and Hall, London, 1981. 2 US Environmental Protection Agency, Control Techniques for Lead Air Emissions, EPA-450/2-77-012, 1977. 3 L. Friberg, T. KjeUstr6m, G.T. Nordberg and M. Piscator+ Cadium, In L. Fribert, G.F. Nordberg and V.B. Vouk (Eds.), Handbook on the Toxicology of Metals, Elsevier, Amsterdam, 1979, 355 pp. 4 M. Stoeppler, Cadmium, In E. Merian, M. Geldmachervon Mallinckrodt, G. Machata, H.W. Niirnberg, H.W. Schlipk6ter and W. Stumm (Eds.), Hrsg., Metalle in der Umwelt, VerlagChemie, Weinheim/Bergstr, 1984, 375 pp. 5 I.D. Schladot and H.W. Niirnberg, Atmosph/irische
161
H.M. AI-Swaidan / Sci. Total Environ. 145 (1994) 157-161
6
7
8
9
Belastung durch toxische Metalle in der Bundesrepublik Deutschland, Emission und Deposition, Jiil-Ber, 1982, 1776. R.S. Houk and J.J. Thompson, Inductively coupled plasma mass spectrometry. Mass Spectrom. Rev., 7 (1988) 425. G.M Hieftje and G.H. Vickers, Developments in plasma source/mass spectrometry. Anal. Chim. Acta, 216 (1989) 1. H.D. Narres, C. Mohl and M. Stoeppler, Metal analysis in difficult materials with platform furnace Zeemanatomic absorption spectrometry. Int. J. Environ. Anal. Chem., 18 (1984) 267. H.M. AI-Swaidan, Simultaneous determination of trace metals in Saudi Arabian crude oil products by inductively
10 11 12
13 14
coupled plasma mass spectrometry (1CP/MS). Anal. Lett., 21 (1988) 1487. V. Valkovic, Trace elements in petroleum, Petroleum Publishing, Tulsa, OK, 1978. R.S. Houk, Mass spectrometry of inductively coupled plasmas. Anal. Chem., 56 (1986)97A. C.J. Lord, Determination of trace metals in crude oils by inductively coupled plasma mass spectrometry with microemulsion sample introduction. Anal. Chem, 63 (1991) 1594. ICP/MS Operators Manual, Sciex Elan, 55 Glen Cameron Road, Thurnhill, Ontario, Canada, 1984. DGMK-Berichte, Forschungsbericht 264, Bestimmung von cadmium in Mineral 61 produkten, Hamburg, 1983.