Speciation of Arsenic in Rice by High-Performance Liquid Chromatography–Inductively Coupled Plasma Mass Spectrometry

Mitigating translocation of arsenic from rice field to soil pore solution by manipulating the redox conditions

Arsenic (As) is uptaken more readily by rice over wheat and barley. The exposure of As to humans being in the rice-consuming regions is a serious issue. Thus, an effective practice to reduce the translocation of As from soil to rice grain should be implemented. During a flooding period, the water layer greatly limits the transport of oxygen from atmosphere to soil, which provides favorable conditions for reduction of oxygen. The reduction of Fe in the soil during the flooding condition is closely related to the As mobility, which expedites the release of As to the soil pore solution and increases As uptake by rice plants. Therefore, the performance of oxygen releasing compounds (ORCs) was evaluated to lower the translocation of As from soil to soil solution. Specifically, in the simple system containing ORCs and water, the oxygen releasing capacity of ORCs was scrutinized. In addition, ORCs was applied to sea sand and arsenic bearing ferrihydrite to identify the contribution of ORCs to As and iron mobility. Especially, ORCs were introduced to the closed (completely mixed system) and open (static) systems to simulate the paddy soil environment. Introducing ORCs increased the DO in the aqueous phase, and CaO₂ was more effective in increasing DO than MgO₂. In the static system simulating a rice field, the dissolution of ORCs was inhibited. The pH increased due to the formation of hydroxide, but the increase was not significant in the soil due to the buffering capacity of the soil. Finally, the As concentration in the soil solution was lowered to 25-50% of that of the control system by application of ORCs in the static paddy soil system. All experimental findings signify that the application of ORCs can be an effective practice to lower the translocation of As from soil to pore solution.

Arsenic Species Analysis at Trace Level by High Performance Liquid Chromatography with Inductively Coupled Plasma Mass Spectrometry

A sensitive and accurate simultaneous continuous analysis for six arsenic species including arsenobetaine (AsB), arsenocholine (AsC), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenite (As^III), and arsenate (As^V) has been developed by high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). An anion-exchange column of Hamilton PRP-X100 (Switzerland) was applied for separation of the six arsenic species with gradient elution of 1.25 mmol/L Na₂HPO₄ and 11.0 mmol/L KH₂PO₄ as the mobile phase A and 2.5 mmol/L Na₂HPO₄ and 22.0 mmol/L KH₂PO₄ as the mobile phase B. The linearity ranges for AsB, AsC, MMA, DMA, As^III, and As^V were between 0.5 and 50.0 μg/L, and the detection limits of the six arsenic species were all within 0.01–0.35 ng/L. The relative standard deviations (RSDs) were within 2.26–3.68% and the recovery rates of samples ranged from 95 to 103%. The proposed method was applied for the arsenic speciation analysis of sediment pore-water samples, which were taken from the supernatant after centrifugation and filtration.

Inorganic arsenic content in Ecuadorian rice-based products

Arsenic intake in the world is linked with drinking water and food; the main sources of inorganic As (i-As) exposure in food are rice and rice-based products. The consumption of rice in Ecuador is 53.2 kg year^-1 and it is the most commonly used cereal for the preparation of many popular dishes especially for subjects with celiac disease. Objectives of this research were: (i) to determine the content of i-As in foods widely consumed by Ecuadorians with celiac disease, (ii) to calculate the i-As dietary intake, and (iii) to model and predict the health risks of the population under study as a result of their exposure to i-As from rice-based food. The estimated daily intakes of Ecuadorian children (below 3 years of age) and adults were established at 0.52 and 0.55 μg kg^-1 body weight d^-1, respectively. These values were above the lower BMDL₀₁ value established for i-As established by the EFSA; consequently, it can be concluded that health risk cannot be excluded for the Ecuadorian population with celiac disease.

Determination of macro, micro and trace elements in citrus fruits by inductively coupled plasma-optical emission spectrometry (ICP-OES), ICP-mass spectrometry and direct mercury analyzer

BACKGROUND

Citrus fruits are widely consumed around the world. Several elements are known to have important physiological functions in living things, whereas others are reported to have toxic effects. This study was aimed to analyze the concentration of macro, micro and trace elements in citrus fruit varieties. Samples were acid digested using a microwave system and analyzed for macro elements by inductively coupled plasma-optical emission spectrometry (ICP-OES) and for micro and trace elements by inductively coupled plasma-mass spectrometry (ICP-MS). The application of analytical techniques was analyzed by determining method validation parameters including limits of detection and quantification, linearity, precision, spiking experiments and analyzing certified reference material (NIST CRM-1570a), Spinach leaves.

RESULTS

The elemental levels of citrus fruits were found largely to be dependent upon the type of analyzed samples. Among nutritionally important elements, citrus fruits were good sources of potassium (95.13-270.4 mg kg^-1 ), calcium (10.57-75.29 mg kg^-1 ), zinc (466.5-1611 µg kg^-1 ) and manganese (35.35-1902 µg kg^-1 ). The concentrations of toxic elements (Pb, Cd, As, Al, Hg) were very low.

CONCLUSION

In general, the concentrations of analyzed elements were within the critical levels specified by the Food and Agriculture Organization/World Health Organization and Food and Nutrition Board USA. Linear discriminant analysis successfully separated the samples into clear groups with 93.9% correct classification. © 2018 Society of Chemical Industry.

An alternative analytical method for determining arsenic species in rice by using ion chromatography and inductively coupled plasma-mass spectrometry

Qualitative and quantitative determination of total arsenic content and arsenic species in rice is very important because rice is one of the main sources of human arsenic intake. However, extraction and determination of arsenic species in rice has been very difficult due to severe matrix interference. An alternative analytical method was developed in this study to determine arsenic species in rice by using ion chromatography coupled to inductively coupled plasma-mass spectrometry. Two internal standards were used. The first internal standard was injected before sample introduction to correct signal change with time. The second internal standard was spiked into the sample to reduce matrix interference. Using the developed method, recoveries of dimethylarsinic acid, monomethylarsonic acid, and inorganic arsenic compared to certified values (NIST SRM 1568b rice flour) were 116%, 107%, and 92%, respectively.

Inorganic arsenic contents in infant rice powders and infant rice snacks marketed in Korea determined by a highly sensitive gas chromatography-tandem mass spectrometry following derivatization with British Anti-Lewisite

Toxic inorganic arsenic (iAs) has been reported to be present in high quantity in rice and rice-based products. The inorganic arsenic contents in infant foods (n = 59) of ready-to-cook infant rice powders and infant rice snacks marketed in Korea were determined by a highly sensitive gas chromatography-tandem mass spectrometry (GC-MS/MS). The mean iAs contents in the infant rice powder and infant rice snacks were 65.6 and 54.0 μg/kg, respectively. The percentages of rice powders and rice snack containing iAs over the maximum level (100 μg/kg) set by EU for the infant foods were found to be 21, and 6%, respectively. This result clearly suggested that regulation regarding the maximum limit of iAs levels for the baby rice products is urgently needed to be set in Korea. This represents the first report on the iAs levels in ready-to-cook infant rice powder products and infant snacks marketed in Korea.

Inorganic arsenic contents in ready-to-eat rice products and various Korean rice determined by a highly sensitive gas chromatography-tandem mass spectrometry

Rice and rice products have been reported to contain high contents of toxic inorganic arsenic (iAs). The inorganic arsenic contents in microwavable ready-to-eat rice products (n=30) and different types of Korean rice (n=102) were determined by a gas chromatography-tandem mass spectrometry (GC-MS/MS). The method showed low limit of detection (0.015pg), high intra- and inter-day repeatability (<7.3%, RSD), and recovery rates (90-117%). The mean iAs content in the ready-to-eat rice products was 59μgkg^-1 (dry weight basis). The mean iAs contents in polished white, brown, black, and waxy rice were 65, 109, 91, and 66μgkg^-1, respectively. The percentages of ready-to-eat rice products, white, brown, black, and waxy rice containing iAs over the maximum level (100μgkg^-1) set by EU for the infant foods were 17, 4, 70, 36 and 0%, respectively.