- Email: [email protected]
Instrumental Neutron Activation Analysis of Selected Elements in Thai Jasmine Rice
Available online at www.sciencedirect.com
ScienceDirect Energy Procedia 89 (2016) 361 – 365
CoE on Sustainable Energy System (Thai-Japan), Faculty of Engineering, Rajamangala University of Technology Thanyaburi (RMUTT), Thailand
Instrumental neutron activation analysis of selected elements in Thai jasmine rice Supalak Kongsria,*, Wannee Srinuttrakulb, Phachirarat Solab, Arporn Busamongkola a
Nuclear Research and Development Division, Thailand Institute of Nuclear Technology (Public Organization), 16 Vibhavadee Rangsit road, Chaktuchak, Bangkok 10900, Thailand. b Nuclear Research and Development Division, Thailand Institute of Nuclear Technology (Public Organization), 9/9 Moo 7 Tambol Saimoon, Amphur Ongkarak, Nakornnayok 26120, Thailand.
Abstract Thai jasmine rice (Khao Dawk Mali 105) grown from different cultivation areas within Tung Kula Rong Hai zone in the northeast of Thailand was studied. The essential (Mn and K) and toxic elements (As and Br) in rice samples were determine using instrumental neutron activation analysis under the irradiation and counting facilities available at the Thai Research Reactor with thermal neutron flux of 1.8 x 109 cm-2 s-1 at the Thailand Institute of Nuclear Technology in Bangkok. The Rice Flour (1568a) certified reference material was simultaneously analyzed with the rice samples, the results shown a reliability and reproducibility of this method. Detection limits were obtained in the range of 0.01–1.44 mg kg-1. The results revealed that the rice samples accumulate the elements at different concentrations. The essential elements including Mn and K are present in significant concentrations. Toxic elements (As and Br) are shown at trace levels. © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
© 2016 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 12th EMSES 2015. Peer-review under responsibility of the organizing committee of the 12th EMSES 2015
Keywords: Thai jasmine rice; Neutron activation analysis; Essential element; Toxic element
1. Introduction Rice is a staple crop for Thai population and is grown mainly in Thailand, especially in northeastern and northern regions. Tung Kula Rong Hai is the most jasmine rice production area in northeastern (Isan) Thailand for
* Corresponding author. Tel.:+662-562-0121; fax: +662-562-0121. E-mail address: [email protected]
1876-6102 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 12th EMSES 2015 doi:10.1016/j.egypro.2016.05.047
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Supalak Kongsri et al. / Energy Procedia 89 (2016) 361 – 365
cultivation of growing of Khao Hom Mali Rice, well-known as Thai Jasmin Rice for consumers around the world >1,2@. However, the Tung Kula Rong Hai area is faced with various problems such as soil deterioration, lessening rice quality and aroma, lack of internationally standardized management and production leading to low product value. Therefore, some cultivators use fertilizers in order to increase crop production and to improve the properties of the nutrient-deficient lands. Fertilizers, especially, the chemical fertilizers in agriculture used to improve the soil properties, could be a potential source of environmental pollution because some fertilizers contain heavy metals, accumulating in soil and plant system >3@. The elements composition of plant can reflect the soil properties. Some metals are not essential nutrients for plants. However, so much high contaminations of metals may become detrimental to human health because they can transfer into the human food chain. Therefore, it is necessary to monitor the levels of essential, non-essential and toxic elements in rice in order to increase our information of the distribution of trace elements both geographically and the food chain. Several methods such as inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS) and graphite furnace atomic absorption spectrometry (GF-AAS) have been used for the analysis of multi-element in foods which are of interest because of their effect on human health >4-6@. It is known that instrument neutron activation analysis (INAA) is a powerful technique for the determination of various elements which play an important role in human health >7@. It is also a non-destructive, versatile, sensitive, multi- element analytical technique with a very low detection limits that can be used for the investigation of rice samples. The objective of this work is to determine the elemental concentrations in Thai jasmine rice using INAA. Data from this study would provide an invaluable source of both essential and toxic elements in the information database of Thai jasmine rice and an attempt for explain variation in elemental contents from different geographical zones. 2. Materials and methods 2.1. Sample collection Fifty paddy jasmine rice samples collected from 10 districts in the Tung Kula Rong Hai area are represented as M1-M10. This area is located in the provinces of Surin, Mahasarakham, Sisaket, Roi Et and Yasothon. In each district, the samples were obtained from 5 different sampling areas. 2.2. Sample preparation The rice samples were air-dried at room temperature, crushed to a homogeneous fine powder by blender. The dried samples were grinded using mortar until homogenized powder and then oven-dried at 60 °C. Samples (approximately 100 mg) were sealed in polyethylene bags prior to neutron irradiation. These containers were packed into rabbit for medium irradiation. The properties of used radionuclides, J-energies, and other details of the analysis are presented in Table 1. Table 1. Nuclear parameters of all elements interested. Element
Radionuclide
Half-life
J-ray (keV)
Irradiation time (h)
As
76
As
26.3 h
559.1
7
Br
82
Br
1.47 days
776.5
7
Mn
56
Mn
2.58 h
846.8
7
K
42
K
12.36 h
1524.6
7
2.3. Gamma-ray spectrometry After the appropriate decay times, all elements were analyzed by J-spectrometry (EG&ORTEC, USA) using a high purity germanium (HPGe) detector with relative efficiency of 60% and resolution of 1.95 keV for 1332.5 keV peak of 60Co. The J-ray spectra were processed using the Gamma Vision-32 computer program. For the energy
363
Supalak Kongsri et al. / Energy Procedia 89 (2016) 361 – 365
calibration of the system, two radionuclide sources, Cs-137 and Co-60 were calibrated covering energy range from 661.7 keV to 1332.51 keV. The data from multichannel analyzer (MCA) combined with central computer facility and calculations. The J-ray activities of samples were counted using the counting time of 1,800 s for all elements. Some examples of how your references should be listed are given at the end of this template in the ‘References’ section, which will allow you to assemble your reference list according to the correct format and font size. 3. Results and discussion In order to check the reliability of the method, the precision and the accuracy of the results were evaluated by analyzing the certified reference materials NIST 1568a. The accuracy, precision and limit of detection (LOD) of all elements are shown in Table 2. Table 2. Comparison of measured values of elemental concentration (in mg kg-1 unless % is indicated) with certified values in Rice flour (NIST, 1568a) standard reference material. Values represent means ± standard error (n = 10). NIST 1568a Element
Certified value
%RSD
LOD ( mg kg-1)
-1
Measured value -1
As
0.29±0.03 (mg kg )
0.28±0.34 (mg kg )
4.5
0.01
Br
8 (mg kg-1)
7.90±1.3 (mg kg-1)
3.0
0.1
-1
-1
Mn
20.0±1.6 (mg kg )
19.7±1.5 (mg kg )
3.7
0.6
K
0.128±0.0008 (%)
0.127±0.8 (%)
2.3
14
The results show that our data for all elements in Rice Flour (NIST, 1568a) were in a good agreement with the certified values. Relative standard deviations (%RSD) were below 5%. The results obtained indicate the viability of using the INAA for the determination of As, Mn, Br, and K in fifty rice samples from Tung Kula Rong Hai area was present in Table 3 and Fig. 1. Table 3. Mean values of element concentrations determined in jasmine rice from Tung Kula Rong Hai in the northeast of Thailand. Sample
Concentration As
Br -1
M1 M2 M3 M4 M5 M6 M7 M8 M9 M10
Mn -1
K -1
(mg kg )
(mg kg )
(mg kg )
(%)
0.07-0.16 0.12-0.15 0.04-0.17 0.05-0.19 0.04-0.16 0.07-0.23 0.13-0.28 0.09-0.40 0.07-0.21 0.16-0.33
0.15-0.74 <0.10 0.14-0.75 0.11-0.21 0.10-0.19 0.10-0.20 0.17-0.30 0.14-0.21 0.12-0.22 0.13-0.28
10.20-14.54 12.54-19.45 16.73-25.17 9.44-13.21 11.69-20.00 9.63-17.59 8.22-13.44 11.87-14.66 10.23-15.23 11.10-17.25
0.09-0.11 0.12-0.17 0.12-0.15 0.10-0.14 0.12-0.16 0.12-0.17 0.11-0.15 0.12-0.13 0.10-0.14 0.08-0.14
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Supalak Kongsri et al. / Energy Procedia 89 (2016) 361 – 365
Fig.1. Various elements in jasmine rice samples collected from Tung Kula Rong Hai area, northeastern Thailand. (The obtained Mn concentrations were the values presented in the graph multiplied by 10.)
The order of concentration for all elements in jasmine rice was K >Mn > Br > As. The jasmine rice contains potassium (K) as a major element, the K content of jasmine rice samples was found in the range of 0.08% to 0.17%. Potassium is an essential to human body and it is also cofactor in many enzymes involved in protein synthesis, energy transfer and the storage of carbohydrates for use as fuel in muscles [5,8]. The manganese (Mn) concentrations in rice samples were ranging from 8.22 to 25.17 mg kg-1. Mn is essential to human life. The role of Mn can act as an enzyme activator for several enzymes and as a component of some metalloenzymes. It is also necessary for the growth of bone, carbohydrate and lipid metabolism [8]. The arsenic (As) concentrations of the jasmine rice samples were in a range of 0.04–0.40 mg kg-1. As occurs naturally in the soil environment, and it has different chemical and toxicological properties [9]. As can cause lung and skin cancers and may cause other cancers. Moreover, another important source of arsenic is the use of agrochemicals in paddy field such as a fertilizer, hormone, fungicide, insecticide or soil treatment that improves the production of crop. The bromine (Br) content in rice samples were found in the range of 0.1-0.75 mg kg-1. The amount of Br in jasmine rice is dependent on the soil composition. The application of agricultural chemicals such as methyl bromide caused the presence of high amounts of bromine [4,8].
Supalak Kongsri et al. / Energy Procedia 89 (2016) 361 – 365
4. Conclusion The proposed method is reliable for the determination of 4 elements in jasmine rice samples by instrumental neutron activation analysis. The jasmine rice samples were a rich source of minor elemental such as, K and Mn, along with As and Br in trace amounts. Mean elemental contents vary over a wide range, ascribed to variable geoenvironmental conditions, local soil characteristics, chemical and agricultural fertilizers. The good agreement between found values and the certified reference values (NIST 1568a) indicated high accuracy and precision of the proposed method.
Acknowledgements The work was supported by Nuclear Research and Development Division, Thailand Institute of Nuclear Technology (Public Organization). References [1] Wangsomnuk PP, Saenprom K, Poosittisak S, Pongdontri P, Srivong P, Wangsomnuk P, Polthanee A, Kosittrakun M. Cultivar and farming practice affect yield and quality of Thai rice. As. J. Food Ag-Ind 2009;336–342. [2] Srinuttrakul W, Busamongkol A. Elemental Analysis of Brown Rice by Inductively Coupled Plasma Atomic Emission Spectrometry and Instrumental Neutron Activation Analysis. Energy Procedia 2014;56:85–91. [3] Savci S. An Agricultural Pollutant: Chemical Fertilizer. IJESD 2012;3:77-80. [4] Antoine JMR, Fung LAH, Grant CN, Dennis HT, Lalor GC. Dietary intake of minerals and trace elements in rice on the Jamaican market, J. Food Comp. Anal 2012;26:111–21. [5] Qian Y, Chen C, Zhang Q, Li Y, Chen Z, Li M. Concentrations of cadmium, lead, mercury and arsenic in Chinese market milled rice and associated population health risk. Food Control 2010; 21:1757-63. [6] Ogiyama S, Tagami K, Uchida S. The concentration and distribution of essential elements in brown rice associated with the polishing rate: Use of ICP-AES and Micro-PIXE. Nucl. Instr. Meth. Phys. Res. B 2008;266: 3625–32. [7] Laoharojanaphand S, Busamongkol A, Permnamtip V, Judprasong K, Chatt A. A pilot study to measure levels of selected elements in Thai foods by instrumental neutron activation analysis. J. Radioanal. Nucl. Chem 2012;294:323–327. [8] Nedjimi B, Beladel B, Guit B. Multi-element determination in medicinal Juniper tree (Juniperus phoenicea) by instrumental neutron activation analysis. J. Radiat. Res. Appl. Sci 2015;http://dx.doi.org/10.1016/j.jrras.2015.01.009. [9] Welna M, Szymczych-Madeja A, Pohl P. Comparison of strategies for sample preparation prior to spectrometric measurements for determination and speciation of arsenic in rice. Trends Analyt Chem 2015;65:122–136.
365
ScienceDirect Energy Procedia 89 (2016) 361 – 365
CoE on Sustainable Energy System (Thai-Japan), Faculty of Engineering, Rajamangala University of Technology Thanyaburi (RMUTT), Thailand
Instrumental neutron activation analysis of selected elements in Thai jasmine rice Supalak Kongsria,*, Wannee Srinuttrakulb, Phachirarat Solab, Arporn Busamongkola a
Nuclear Research and Development Division, Thailand Institute of Nuclear Technology (Public Organization), 16 Vibhavadee Rangsit road, Chaktuchak, Bangkok 10900, Thailand. b Nuclear Research and Development Division, Thailand Institute of Nuclear Technology (Public Organization), 9/9 Moo 7 Tambol Saimoon, Amphur Ongkarak, Nakornnayok 26120, Thailand.
Abstract Thai jasmine rice (Khao Dawk Mali 105) grown from different cultivation areas within Tung Kula Rong Hai zone in the northeast of Thailand was studied. The essential (Mn and K) and toxic elements (As and Br) in rice samples were determine using instrumental neutron activation analysis under the irradiation and counting facilities available at the Thai Research Reactor with thermal neutron flux of 1.8 x 109 cm-2 s-1 at the Thailand Institute of Nuclear Technology in Bangkok. The Rice Flour (1568a) certified reference material was simultaneously analyzed with the rice samples, the results shown a reliability and reproducibility of this method. Detection limits were obtained in the range of 0.01–1.44 mg kg-1. The results revealed that the rice samples accumulate the elements at different concentrations. The essential elements including Mn and K are present in significant concentrations. Toxic elements (As and Br) are shown at trace levels. © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
© 2016 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 12th EMSES 2015. Peer-review under responsibility of the organizing committee of the 12th EMSES 2015
Keywords: Thai jasmine rice; Neutron activation analysis; Essential element; Toxic element
1. Introduction Rice is a staple crop for Thai population and is grown mainly in Thailand, especially in northeastern and northern regions. Tung Kula Rong Hai is the most jasmine rice production area in northeastern (Isan) Thailand for
* Corresponding author. Tel.:+662-562-0121; fax: +662-562-0121. E-mail address: [email protected]
1876-6102 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 12th EMSES 2015 doi:10.1016/j.egypro.2016.05.047
362
Supalak Kongsri et al. / Energy Procedia 89 (2016) 361 – 365
cultivation of growing of Khao Hom Mali Rice, well-known as Thai Jasmin Rice for consumers around the world >1,2@. However, the Tung Kula Rong Hai area is faced with various problems such as soil deterioration, lessening rice quality and aroma, lack of internationally standardized management and production leading to low product value. Therefore, some cultivators use fertilizers in order to increase crop production and to improve the properties of the nutrient-deficient lands. Fertilizers, especially, the chemical fertilizers in agriculture used to improve the soil properties, could be a potential source of environmental pollution because some fertilizers contain heavy metals, accumulating in soil and plant system >3@. The elements composition of plant can reflect the soil properties. Some metals are not essential nutrients for plants. However, so much high contaminations of metals may become detrimental to human health because they can transfer into the human food chain. Therefore, it is necessary to monitor the levels of essential, non-essential and toxic elements in rice in order to increase our information of the distribution of trace elements both geographically and the food chain. Several methods such as inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS) and graphite furnace atomic absorption spectrometry (GF-AAS) have been used for the analysis of multi-element in foods which are of interest because of their effect on human health >4-6@. It is known that instrument neutron activation analysis (INAA) is a powerful technique for the determination of various elements which play an important role in human health >7@. It is also a non-destructive, versatile, sensitive, multi- element analytical technique with a very low detection limits that can be used for the investigation of rice samples. The objective of this work is to determine the elemental concentrations in Thai jasmine rice using INAA. Data from this study would provide an invaluable source of both essential and toxic elements in the information database of Thai jasmine rice and an attempt for explain variation in elemental contents from different geographical zones. 2. Materials and methods 2.1. Sample collection Fifty paddy jasmine rice samples collected from 10 districts in the Tung Kula Rong Hai area are represented as M1-M10. This area is located in the provinces of Surin, Mahasarakham, Sisaket, Roi Et and Yasothon. In each district, the samples were obtained from 5 different sampling areas. 2.2. Sample preparation The rice samples were air-dried at room temperature, crushed to a homogeneous fine powder by blender. The dried samples were grinded using mortar until homogenized powder and then oven-dried at 60 °C. Samples (approximately 100 mg) were sealed in polyethylene bags prior to neutron irradiation. These containers were packed into rabbit for medium irradiation. The properties of used radionuclides, J-energies, and other details of the analysis are presented in Table 1. Table 1. Nuclear parameters of all elements interested. Element
Radionuclide
Half-life
J-ray (keV)
Irradiation time (h)
As
76
As
26.3 h
559.1
7
Br
82
Br
1.47 days
776.5
7
Mn
56
Mn
2.58 h
846.8
7
K
42
K
12.36 h
1524.6
7
2.3. Gamma-ray spectrometry After the appropriate decay times, all elements were analyzed by J-spectrometry (EG&ORTEC, USA) using a high purity germanium (HPGe) detector with relative efficiency of 60% and resolution of 1.95 keV for 1332.5 keV peak of 60Co. The J-ray spectra were processed using the Gamma Vision-32 computer program. For the energy
363
Supalak Kongsri et al. / Energy Procedia 89 (2016) 361 – 365
calibration of the system, two radionuclide sources, Cs-137 and Co-60 were calibrated covering energy range from 661.7 keV to 1332.51 keV. The data from multichannel analyzer (MCA) combined with central computer facility and calculations. The J-ray activities of samples were counted using the counting time of 1,800 s for all elements. Some examples of how your references should be listed are given at the end of this template in the ‘References’ section, which will allow you to assemble your reference list according to the correct format and font size. 3. Results and discussion In order to check the reliability of the method, the precision and the accuracy of the results were evaluated by analyzing the certified reference materials NIST 1568a. The accuracy, precision and limit of detection (LOD) of all elements are shown in Table 2. Table 2. Comparison of measured values of elemental concentration (in mg kg-1 unless % is indicated) with certified values in Rice flour (NIST, 1568a) standard reference material. Values represent means ± standard error (n = 10). NIST 1568a Element
Certified value
%RSD
LOD ( mg kg-1)
-1
Measured value -1
As
0.29±0.03 (mg kg )
0.28±0.34 (mg kg )
4.5
0.01
Br
8 (mg kg-1)
7.90±1.3 (mg kg-1)
3.0
0.1
-1
-1
Mn
20.0±1.6 (mg kg )
19.7±1.5 (mg kg )
3.7
0.6
K
0.128±0.0008 (%)
0.127±0.8 (%)
2.3
14
The results show that our data for all elements in Rice Flour (NIST, 1568a) were in a good agreement with the certified values. Relative standard deviations (%RSD) were below 5%. The results obtained indicate the viability of using the INAA for the determination of As, Mn, Br, and K in fifty rice samples from Tung Kula Rong Hai area was present in Table 3 and Fig. 1. Table 3. Mean values of element concentrations determined in jasmine rice from Tung Kula Rong Hai in the northeast of Thailand. Sample
Concentration As
Br -1
M1 M2 M3 M4 M5 M6 M7 M8 M9 M10
Mn -1
K -1
(mg kg )
(mg kg )
(mg kg )
(%)
0.07-0.16 0.12-0.15 0.04-0.17 0.05-0.19 0.04-0.16 0.07-0.23 0.13-0.28 0.09-0.40 0.07-0.21 0.16-0.33
0.15-0.74 <0.10 0.14-0.75 0.11-0.21 0.10-0.19 0.10-0.20 0.17-0.30 0.14-0.21 0.12-0.22 0.13-0.28
10.20-14.54 12.54-19.45 16.73-25.17 9.44-13.21 11.69-20.00 9.63-17.59 8.22-13.44 11.87-14.66 10.23-15.23 11.10-17.25
0.09-0.11 0.12-0.17 0.12-0.15 0.10-0.14 0.12-0.16 0.12-0.17 0.11-0.15 0.12-0.13 0.10-0.14 0.08-0.14
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Supalak Kongsri et al. / Energy Procedia 89 (2016) 361 – 365
Fig.1. Various elements in jasmine rice samples collected from Tung Kula Rong Hai area, northeastern Thailand. (The obtained Mn concentrations were the values presented in the graph multiplied by 10.)
The order of concentration for all elements in jasmine rice was K >Mn > Br > As. The jasmine rice contains potassium (K) as a major element, the K content of jasmine rice samples was found in the range of 0.08% to 0.17%. Potassium is an essential to human body and it is also cofactor in many enzymes involved in protein synthesis, energy transfer and the storage of carbohydrates for use as fuel in muscles [5,8]. The manganese (Mn) concentrations in rice samples were ranging from 8.22 to 25.17 mg kg-1. Mn is essential to human life. The role of Mn can act as an enzyme activator for several enzymes and as a component of some metalloenzymes. It is also necessary for the growth of bone, carbohydrate and lipid metabolism [8]. The arsenic (As) concentrations of the jasmine rice samples were in a range of 0.04–0.40 mg kg-1. As occurs naturally in the soil environment, and it has different chemical and toxicological properties [9]. As can cause lung and skin cancers and may cause other cancers. Moreover, another important source of arsenic is the use of agrochemicals in paddy field such as a fertilizer, hormone, fungicide, insecticide or soil treatment that improves the production of crop. The bromine (Br) content in rice samples were found in the range of 0.1-0.75 mg kg-1. The amount of Br in jasmine rice is dependent on the soil composition. The application of agricultural chemicals such as methyl bromide caused the presence of high amounts of bromine [4,8].
Supalak Kongsri et al. / Energy Procedia 89 (2016) 361 – 365
4. Conclusion The proposed method is reliable for the determination of 4 elements in jasmine rice samples by instrumental neutron activation analysis. The jasmine rice samples were a rich source of minor elemental such as, K and Mn, along with As and Br in trace amounts. Mean elemental contents vary over a wide range, ascribed to variable geoenvironmental conditions, local soil characteristics, chemical and agricultural fertilizers. The good agreement between found values and the certified reference values (NIST 1568a) indicated high accuracy and precision of the proposed method.
Acknowledgements The work was supported by Nuclear Research and Development Division, Thailand Institute of Nuclear Technology (Public Organization). References [1] Wangsomnuk PP, Saenprom K, Poosittisak S, Pongdontri P, Srivong P, Wangsomnuk P, Polthanee A, Kosittrakun M. Cultivar and farming practice affect yield and quality of Thai rice. As. J. Food Ag-Ind 2009;336–342. [2] Srinuttrakul W, Busamongkol A. Elemental Analysis of Brown Rice by Inductively Coupled Plasma Atomic Emission Spectrometry and Instrumental Neutron Activation Analysis. Energy Procedia 2014;56:85–91. [3] Savci S. An Agricultural Pollutant: Chemical Fertilizer. IJESD 2012;3:77-80. [4] Antoine JMR, Fung LAH, Grant CN, Dennis HT, Lalor GC. Dietary intake of minerals and trace elements in rice on the Jamaican market, J. Food Comp. Anal 2012;26:111–21. [5] Qian Y, Chen C, Zhang Q, Li Y, Chen Z, Li M. Concentrations of cadmium, lead, mercury and arsenic in Chinese market milled rice and associated population health risk. Food Control 2010; 21:1757-63. [6] Ogiyama S, Tagami K, Uchida S. The concentration and distribution of essential elements in brown rice associated with the polishing rate: Use of ICP-AES and Micro-PIXE. Nucl. Instr. Meth. Phys. Res. B 2008;266: 3625–32. [7] Laoharojanaphand S, Busamongkol A, Permnamtip V, Judprasong K, Chatt A. A pilot study to measure levels of selected elements in Thai foods by instrumental neutron activation analysis. J. Radioanal. Nucl. Chem 2012;294:323–327. [8] Nedjimi B, Beladel B, Guit B. Multi-element determination in medicinal Juniper tree (Juniperus phoenicea) by instrumental neutron activation analysis. J. Radiat. Res. Appl. Sci 2015;http://dx.doi.org/10.1016/j.jrras.2015.01.009. [9] Welna M, Szymczych-Madeja A, Pohl P. Comparison of strategies for sample preparation prior to spectrometric measurements for determination and speciation of arsenic in rice. Trends Analyt Chem 2015;65:122–136.
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