Inter-laboratory validation of an inexpensive streamlined method to measure inorganic arsenic in rice grain

Speciation of trace amounts of Sb(III) and Sb(V) in environmental water using inductively coupled plasma mass spectrometry after magnetic solid-phase extraction with rGO/Fe3O4

We developed an approach of magnetic dispersive solid-phase extraction (MSPE) based on magnetic graphene nanocomposite rGO/Fe3O4 for the determination of trace Sb(III) and Sb(V) using inductively coupled plasma mass spectrometry (ICP-MS). Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the sorbent. The adsorption behavior of Sb(III) and Sb(V) on rGO/Fe3O4 was investigated. The results showed that the adsorption capacity of Sb(V) was nearly zero at pH = 9, while Sb(III) could be well adsorbed on rGO/Fe3O4. The magnetic SPE parameters including pH, adsorbent dosage, eluent type, and volume were optimized. The detection limit of Sb(III) under ideal conditions was 6 ng L-1, and the relative standard deviation was 7.6% (c = 1 g L-1, n = 7). The technique was used to identify Sb(III) at trace levels in environmental water samples, and its validity was examined by recovery experiments and the examination of an approved reference material.

Inter-laboratory validation of liquid chromatography-tandem mass spectrometry multi-mycotoxin determination in animal feed - method transfer from the reference laboratory to regional laboratories

Introduction

The results are presented of the inter-laboratory validation of a liquid chromatography-tandem mass spectrometry method for the determination of eight mycotoxins (aflatoxin B1, deoxynivalenol, fumonisin B1, fumonisin B2, ochratoxin A, toxin T-2, toxin HT-2 and zearalenone) in animal feeds.

Material and Methods

This study was an essential part of the method's transfer from the National Reference Laboratory to six regional laboratories in Poland working in the official survey of mycotoxins in feed. The laboratories received a batch of standard solutions, blank samples and quality control materials on which to perform analysis with one procedure and different liquid chromatography-tandem mass spectrometry conditions.

Results

The validation results show good precision (reproducibility coefficient of variation 3.7-20.5%) and accuracy of the method (recovery 89-120% and trueness 94-103%) and sufficient skills of the laboratory personnel.

Conclusion

The study is an example of the successful transfer of the method among laboratories.

Probabilistic estimation and statuses of total, bioaccessible and inorganic arsenic accumulation in commercial white and brown rice in Thailand

Arsenic (As) in rice is a crucial public health concern because it is a human carcinogen. This study was conducted to determine the actual As concentrations and estimate the probable range of As in rice. The status of As accumulation in rice was also determined. White (n=154) and brown (n=54) rice samples were collected over three crop years. The concentrations of As (total, bioaccessible and inorganic) were determined. The total As concentrations in white (0.088-0.295 mg/kg) and brown (0.119-0.517 mg/kg) rice were approximately 58.8% and 57.4% higher than the Codex standards, respectively. However, the bioaccessible and inorganic As in both types of rice were lower than the standards for both rice types. Regarding the classifications of As accumulation (low, normal, high and unusually high), the actual As concentrations found in the rice samples were either in the normal range or a high concentration of As.

Green and Simple Extraction of Arsenic Species from Rice Flour Using a Novel Ultrasound-Assisted Enzymatic Hydrolysis Method

It is well established that arsenic (As) has many toxic compounds, and in particular, inorganic As (iAs) has been classified as a type-1 carcinogen. The measuring of As species in rice flour is of great importance since rice is a staple of the diet in many countries and a major contributor to As intake in the Asian diet. In this study, several solvents and techniques for the extraction of As species from rice flour samples prior to their analysis by HPLC-ICP-MS were investigated. The extraction methods were examined for their efficiency in extracting various arsenicals from a rice flour certified reference material, NMIJ-7532a, produced by the National Metrology Institute of Japan. Results show that ultrasound-assisted extraction at 60 °C for 1 h and then heating at 100 °C for 2.5 h in the oven using a thermostable α-amylase aqueous solution was highly effective in liberating the arsenic species. The recoveries of iAs and dimethylarsinic acid (DMA) in NMIJ-7532a were 99.7% ± 1.6% (n = 3) and 98.1% ± 2.3% (n = 3), respectively, in comparison with the certificated values. Thus, the proposed extraction method is a green procedure that does not use any acidic, basic, or organic solvents. Moreover, this extraction method could effectively maintain the integrity of the native arsenic species of As(III), As(V), monomethylarsonate (MMA), DMA, arsenobetaine (AsB) and arsenocholine (AsC). Under the optimum extraction, chromatography and ICP-MS conditions, the limits of detection (LOD) obtained were 0.47 ng g−1, 1.67 ng g−1 and 0.80 ng g−1 for As(III), As(V) and DMA, respectively, while the limits of quantification (LOQ) achieved were 1.51 ng g−1, 5.34 ng g−1 and 2.57 ng g−1 for As(III), As(V) and DMA, respectively. Subsequently, the proposed method was successfully applied to As speciation analysis for several rice flour samples collected from contaminated areas in China.

Grain Inorganic Arsenic Content in Rice Managed Through Targeted Introgressions and Irrigation Management

Arsenic (As) accumulation in rice grain is a significant public health concern. Inorganic As (iAs) is of particular concern because it has increased toxicity as compared to organic As. Irrigation management practices, such as alternate wetting and drying (AWD), as well as genotypic differences between cultivars, have been shown to influence As accumulation in rice grain. A 2 year field study using a Lemont × TeQing backcross introgression line (TIL) mapping population examined the impact of genotype and AWD severity on iAs grain concentrations. The "Safe"-AWD [35-40% soil volumetric water content (VWC)] treatment did not reduce grain iAs levels, whereas the more severe AWD30 (25-30% VWC) consistently reduced iAs concentrations across all genotypes. The TILs displayed a range of iAs concentrations by genotype, from less than 10 to up to 46 μg kg-1 under AWD30 and from 28 to 104 μg kg-1 under Safe-AWD. TIL grain iAs concentrations for flood treatments across both years ranged from 26 to 127 μg kg-1. Additionally, seven quantitative trait loci (QTLs) were identified in the mapping population associated with grain iAs. A subset of eight TILs and their parents were grown to confirm field-identified grain iAs QTLs in a controlled greenhouse environment. Greenhouse results confirmed the genotypic grain iAs patterns observed in the field; however, iAs concentrations were higher under greenhouse conditions as compared to the field. In the greenhouse, the number of days under AWD was negatively correlated with grain iAs concentrations. Thus, longer drying periods to meet the same soil VWC resulted in lower grain iAs levels. Both the number and combinations of iAs-affecting QTLs significantly impacted grain iAs concentrations. Therefore, identifying more grain iAs-affecting QTLs could be important to inform future breeding efforts for low iAs rice varieties. Our study suggests that coupling AWD practices targeting a soil VWC of less than or equal to 30% coupled with the use of cultivars developed to possess multiple QTLs that negatively regulate grain iAs concentrations will be helpful in mitigating exposure of iAs from rice consumption.

Probabilistic assessment of the daily intake of microelements and toxic elements via the consumption of rice with different degrees of polishing

BACKGROUND

The polishing process plays a key role in determining the beneficial quality of rice. However, the effects of polishing on human exposure to essential and toxic elements are not well reported. This study evaluated the effects of polishing on the levels of essential and toxic elements in rice grains and evaluated the status of their daily intake using probabilistic assessment.

RESULTS

The levels of essential elements decreased as the degree of polishing increased. The highest reduction percentages of essential elements [24% of copper (Cu), 26% of nickel (Ni), and 52% of manganese (Mn)] were found after the first polishing step. The highest zinc (Zn) reduction (15%) was found after the fourth polishing step. For toxic elements, polishing significantly reduced the arsenic (As) concentration (15-31%) from that of the whole grains, of which 26% was removed after the first step.

CONCLUSION

Polishing removed both essential and toxic elements from rice grains. The highest losses of Cu, Mn, Ni, and As were found after the first polishing step since these elements generally localize in the aleurone layers of rice grains. The last polishing step caused a significant Zn reduction from the grain. Polishing had no significant effect on the cadmium (Cd) concentration in grains. The consumption of all types of rice could not supply sufficient amounts of all microelements except Mn to maintain optimum health. Both As and Cd intake levels were lower than the benchmarks of toxic health effects. Thus, the potential health impacts of both of these elements in rice can be neglected. © 2020 Society of Chemical Industry.

CRM rapid response approach for the certification of arsenic species and toxic trace elements in baby cereal coarse rice flour certified reference material BARI-1

With recently legislated maximum levels of inorganic arsenic (iAs) in white and brown rice in Canada, the regulatory bodies are evaluating the need for regulation of As levels in infant food products. Rice is a major part of infants' diet, and therefore, the presence of As in this staple food causes concerns. So far, the scientific community was lacking suitable certified reference material (CRM) which could be used to assess the accuracy of developed analytical methods for As speciation in infants' food products. As a result, we have developed BARI-1, a baby cereal coarse rice flour reference material which was certified for total arsenic (0.248 ± 0.018 mg kg^-1), cadmium (0.0134 ± 0.0014 mg kg^-1), mercury (0.0026 ± 0.0003 mg kg^-1), lead (0.0064 ± 0.0016 mg kg^-1), inorganic As (0.113 ± 0.016 mg kg^-1) and dimethylarsinic acid (DMA) (0.115 ± 0.010 mg kg^-1), and reference value for monomethylarsonic acid (MMA) (0.0045 ± 0.0008 mg kg^-1) was reported. We also observed trace amounts of an unknown As compound, with chromatographic retention time close to DMA. Participating laboratories were allowed to use their in-house-validated extraction and/or digestion methods, and the detection of total metals was done by ICP-MS whereas HPLC-ICP-MS was used for As speciation. Despite the diversity in sample preparation and quantitation methods, reported values were in good agreement. For iAs measurement, the comparison between hydride generation ICP-MS and HPLC-ICP-MS found iAs overestimation with the former method, possibly due to interference from DMA. The certification was accomplished with a CRM rapid response approach in collaborative, focused effort completing the CRM development in few months instead of the typical multiyear project. This approach allowed to respond to measurement needs in a timely fashion. Graphical abstract.

Rice Flour and Bran Enriched with Blueberry Polyphenols Increases Storage Stability and Decreases Arsenic Content in Bran

A low-cost method utilizing rice co-products to concentrate and stabilize blueberry polyphenols was developed that decreased the arsenic (As) content in rice bran. After concentration at 10 g/L, brown rice flour displayed a higher total anthocyanin content in both blueberry juice (2.7 mg/g) and pomace extract (2.6 mg/g) when compared to white rice flour. Defatted rice bran enriched with blueberry juice (10 g/L) had the highest concentration of polyphenols (16.0 mg/g), and defatted bran enriched with pomace extract had the highest concentration of anthocyanins (5.32 mg/g). Enriched rice flour and bran contained higher levels of anthocyanins when using pomace extracts. Polyphenols and anthocyanins were found to be highly stable at 37 °C in rice flour and bran samples combined with pomace extract. Polyphenol enrichment also produced lower total and inorganic arsenic (i-As) levels in defatted rice bran. Inorganic arsenic (i-As) concentrations in defatted rice bran enriched with blueberry juice and pomace extracts were reduced by 20.5% and 51.6%, respectively. Overall, rice flour and bran that are enriched with polyphenols and anthocyanins from blueberry pomace extracts are shelf and color stable, had low sugar content, and represent unique health-promoting food ingredients.

Validation and inter-laboratory study of selective hydride generation for fast screening of inorganic arsenic in seafood

It is advisable to monitor and regulate inorganic arsenic (iAs) in food and feedstuff. This work describes an update and validation of a method of selective hydride generation (HG) with inductively coupled plasma mass spectrometry (ICP-MS) for high-throughput screening of iAs content in seafood samples after microwave-assisted extraction with diluted nitric acid and hydrogen peroxide. High concentration of HCl (8 M) for HG along with hydrogen peroxide in samples of a same concentration as used for extraction leads to a selective conversion of iAs to volatile arsine that is released and transported to the detector. A minor contribution from methylarsonate (≈20% to iAs) was found, while HG from dimethylarsinate, trimethylarsine oxide is substantially suppressed (less than 1% to iAs). Methodology was applied to Certified Reference Materials (CRMs) TORT-3, DORM-3, DORM-4, DOLT-4, DOLT-5, PRON-1, SQID-1 and ERM-CE278k, in some of them iAs has been determined for the first time, and to various seaweed samples from a local store. The results were always compared with a reference method and selectivity of iAs determination was evaluated. An inter-laboratory reproducibility was tested by comparative analyses of six fish and four seaweed samples in three European laboratories, with good agreement of the results. The method of HG-ICP-MS is sensitive (limit of detection 2 μg kg^-1 iAs), well suited for screening of large number of samples and selective at iAs concentration levels at which maximum limits are expected to be set into EU legislation for marine samples.