Multi-Elemental Risk Assessment of Rice Products Using On-Line Continuous Leaching and Ion Exchange Chromatography Coupled to Inductively Coupled Plasma Mass Spectrometry for the Speciation Analysis of Bio-Accessible Elements
Sadiq, Nausheen Waheed
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There are over 40 000 different types of rice, several of which are known to contain significant amounts of inorganic arsenic (As), i.e. the most toxic form of As. Because rice requires water for cultivation, groundwater has a great impact on rice’s toxic content. Given that over 3 billion people share a diet consisting mainly of rice, risk assessment of toxic species of As, chromium (Cr) and selenium (Se), is important. This thesis investigates both toxic and essential elements in both cooked and uncooked rice, as previous studies have shown that cooking may in fact convert the species of As in rice to the most toxic species. This thesis focuses on organic white and brown rice, basmati rice and baby rice cereal. Baby rice cereal has not been studied previously, despite the fact that itis one of the first foods given to infants, who are at greater risk because of their small weight. Speciation analysis of the bio-accessible fraction was conducted on As, Cr and Se to determine which portion was actually toxic, as some species of these elements are non toxic. To this end, ion-exchange chromatography (IEC) was used to separate the various species of the elements monitored, which were then quantified by performing on-line inductively coupled plasma (ICP) mass spectrometry (MS) analysis of the effluent, i.e. using ICP-MS as a detector for IEC. Electrothermal vaporization (ETV) coupled to ICP optical emission spectrometry (OES) was also used to study glutinous rice that is commonly consumed in Asian countries. The ability to conduct total analysis of the solid without the need for an acid digestion is beneficial in providing a quick and simple screening through determination of the total amount of toxic, potentially toxic and essential elements present in the solid sample. This study focuses on various rice-based samples and the potential risk they pose to human consumption on a regular basis.