University of Cincinnati

U UNIVERSITY OF CINCINNATI Date: I, , hereby submit this original work as part of the requirements for the degree of: in It is entitled: Student Signature: This work and its defense approved by: Committee Chair: Approval of the electronic document: I have reviewed the Thesis/Dissertation in its final electronic format and certify that it is an accurate copy of the document reviewed and approved by the committee. Committee Chair signature: The Toxicity Assessment of Heavy Metals and Their Species in Rice A thesis submitted to the Graduate School of the University of Cincinnati in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE in the Department of Chemistry of the College of Art and Science 2009 by Julie Zhiling Zhang B.S., Chemistry, Jiling University, China, 1989 Committee Chair: Joseph A. Caruso, Ph.D. Abstract There is an accumulation of minerals and other elements in rice. Related to health, and particularly nutritional concerns, twenty (20) rice samples of different varieties and origins obtained from the US market were investigated for twenty-four (24) elements by using inductively coupled plasma mass spectrometry (ICP-MS). Arsenic species in Jasmine brown and white rice (Royal Thailand), Basmati brown and white rice (Royal India), and Nishiki brown and white rice (JFC California, US) were also studied by coupling high performance liquid chromatography (HPLC) with ICP-MS. Selenium species in Basmati brown and white rice (Royal India) were also studied by HPLC-ICP- MS. The study indicates essential elements are accumulated more in brown rice. There are heavy metals of cadmium, lead, antimony, and chromium in the rice samples tested, but the content is not enough for concern. 34 to 333 ppb of arsenic is found in the rice. The arsenic content in the most of white rice samples is in the range of 150 to 225 ppb. The brown rice shows more arsenic. As (III), As (V), and dimethylarsinic acid (DMA) are the species found in the three type of rice and these varied among different rice types. The Basmati rice, regardless to the origins, trends to contain more aluminum and selenium. Little selenium (IV) is presented in Basmati white rice (Royal India). ii Acknowledgements I would like to thank my advisor Dr. Joseph Caruso for his guidance and instruction during the research process. In addition to my advisor, I would also like to recognize my committee member Dr. Thomas Ridgway for his invaluable advices. Heather Trenary and Yaofang Zhang as members of the Caruso group provided a support to me. I would like to put my appreciation on them. The research was completed in the International Paper Cincinnati Technology Center. Providing financial, technological, and knowledge supports, International Paper allowed me to achieve my dream. Mr. Dennis Crawshaw (the International Paper Analytical Science Group Manager), Dr. Ewa Bucher, and Dr. Chuck Lohrke helped and supported me throughout the thesis. I would like to put my gratitude on them. Finally, my acknowledgement is to my family. My husband, George He, and my daughter, Grace He, gave me encouragement that cannot be forgotten. The influx of their euphonious words made this experience more inspiring and joyful. iii Table of Contents Abstract ii Acknowledgement iii List of Figures vii List of Tables ix Chapter I – Introduction 1 1.1 Introduction of rice 2 1.2 Heavy metal accumulation in rice 6 1.3 General toxicological profile of heavy metals 12 1.4 Antagonistic affects between selenium and arsenic 16 1.5 Objective of the research 18 Chapter II – Methodologies 20 2.1 Inductively coupled plasma mass spectrometry (ICP-MS) 20 2.1.1 Instrument description and theory 20 2.1.2 Interference removal with collision and reaction cell 24 2.2 High performance liquid chromatography (HPLC) 28 Chapter III – Experimental 32 3.1 Instrumentation and apparatus 32 3.2 Reagents and standards 34 iv 3.3 Samples 36 3.4 Experimental procedure 39 3.5 Instrument tuning 45 3.6 Determination of detection limit (DL) 46 Chapter IV – Results and discussion 48 4.1 The elemental profile in different rice varieties 48 4.1.1 Detection limits (DL) and limits of quantification (LOQ) of the ICP-MS simultaneous multi-element analysis 48 4.1.3 Quality assurance and quality control (QA/QC) 48 4.1.3 The total element profile in different rice varieties from origins 52 4.2 Trifluoroacetic acid (TFA) extraction 58 4.2.1 Optimization of Collision or reaction gas flow 58 4.2.2 QA/QC issues in TFA extraction 60 4.2.3 Efficiency of TFA extraction 60 4.2.4 Arsenic speciation analysis in TFA extracts 63 4.2.5 Inorganic selenium speciation analysis in Basmati white and brown rice (Royal, India) 70 4.3 Methanol/ water extraction 71 4.3.1 Efficiency of methanol/water (50/50) extraction 71 4.3.2 Arsenic speciation analysis in the methanol/water (50/50) extracts 73 v Chapter V – Conclusions 75 References 78 vi List of Figures Figure 1.1 Diagrams of Rice Plant and Rice Grain Figure 1.2 Images of Rough rice, Brown Rice and White Rice Figure 1.3 Images of long Grain, Medium Grain and Short Grain Rice Figure 2.1 A General schematic of an inductively coupled plasma mass spectrometer Figure 2.2 A schematic of an ICP plasma torch adapted from Agilent ICP-MS Primer Figure 2.3 A schematic of a quadrupole mass analyzer Figure 2.4 Tow possible mechanisms for 40Ar35Cl interference removal in determination of 75As Figure 2.5 The kinetic energy discrimination mechanism Figure 2.6 Coupling HPLC to ICP-MS Figure 2.7 Analyte competitions between stationary and mobile phase Figure 3.1 Photograph of HPLC-ICP-MS used in the study Figure 4.1 The distribution of elemental recoveries in digestion and analytical procedures Figure 4.2 The distribution of P, S, K, and Mg in different rice varieties and origins Figure 4.3 The distribution of Ca, Zn, Mn, Fe, and Na in different rice varieties Figure 4.4 The distribution of Al, Ni, Ba, Ti, and Mo in different rice varieties Figure 4.5 The distribution of As, Cd, Cr, and Pb in different rice varieties Figure 4.6 The profile of arsenic in different rice varieties and origins Figure 4.7 The distributions of Selenium and arsenic vii Figure 4.8 Optimization of the reaction/collision gas flow for arsenic and selenium determination Figure 4.9 Comparison of chromatograms obtained from HPLC-ICP-MS with a Hamilton PRP-100 anion exchange column and Luna SCX 100A column Figure 4.10 The profile of the sum of arsenic species in the Jasmine, Basmati, and Nishiki brown and white rice Figure 4.11 The profile of arsenic species in Basmati brown and white rice, Royal, India Figure 4.12 The profile of arsenic species in Nishiki brown and white rice, JFC California US Figure 4.13 The profile of arsenic species in Jasmine brown and white rice, Royal, Thailand Figure 4.14 Comparison of arsenic species among Jasmine white rice, Nishiki white rice and Basmati white and brown rice Figure 4.15 The chromatograms of inorganic selenium speciation analysis Figure 4.16 The yields of six sequential extractions Figure 4.17 The pH meter responses for several methanol/water mixtures Figure 4.18 The chromatogram of arsenic speciation analysis in methanol/water (50/50) extracts viii List of Tables Table 1.1 Composition of White Rice and Brown Rice adapted from Thai food composition table (1999), Institute of Nutrition, Mahidol University, Thailand Table 1.2 The chemical forms of selected arsenic species and their toxicity Table 2.1 Gases for collision and/or reaction cell Table 3.1 Sample list Table 3.2 Operational parameters for ICP-MS Table 3.3 The HPLC conditions Table 3.4 Target tune values for 1ppb of Agilent tuning solution containing 0.5 % of HCl and 0.1 second integration time Table 4.1 The detection limits (DL) and limits of quantification (LOQ) of ICP-MS simultaneous multi-element analysis Table 4.2 The recovery of calibration verification standards in the analysis of total elements concentration Table 4.3 The total arsenic in TFA extracts and the efficiency of arsenic TFA extraction Table 4.4 The total selenium in TFA extracts and the efficiency of selenium TFA extraction Table 4.5 Quantitative figures of merit Table 4.6 The summary of arsenic speciation analysis Table 4.7 The extraction efficiency of arsenic species in methanol/water (50/50) ix Chapter I - Introduction Rice as the main staple food for half of the world‘s population provides more than one fifth of calories consumed by humans worldwide [1], [2]. In developing countries, rice is a major nutrient source for lower income households. In these families, 30-55% of their total iron comes from rice [3]. Rice is a good micronutrient source of manganese, selenium, magnesium and other essential minerals when grown where these elements are present. White rice, also called milled rice, is the most accepted dietary form. The seeds of the rice plant are first milled to remove the hull becoming brown rice, and the process may be continued to polish the brown rice, producing white rice. The rice spoilage and storage time also can be improved, as the high oil bran tends to make the rice seeds rancid. However, the rice seeds lose the most of their nutrients in this process, because rice bran contains a high level of dietary fiber, lipids, amino acids, various antioxidants, vitamins, cofactors, and dietary minerals. Today, brown rice and wild rice as whole grain rice are suggested to provide more nutrients and health benefits than the more common white rice.

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