Simultaneous determination of arsenic and mercury species in rice by ion-pairing reversed phase chromatography with inductively coupled plasma mass spectrometry
Introduction
Arsenic (As) and mercury (Hg) are well known as toxic elements because of their potential risks to human health. Exposure to As or Hg has been linked to an increased risk of many physiological disorders and various types of cancer (Mir et al., 2007). With the rapid development of modern industry, As and Hg are often present as a result of human activities, such as mining/processing of ore and wood treatment (Afton, Kubachka, Catron, & Caruso, 2008). Since As and Hg can be taken up and accumulated by crops, the safety and quality of agricultural products are subject to serious threats from contaminated sources.
Unfortunately, rice, a staple crop for Chinese people, is very efficient in As and Hg accumulation (Ma et al., 2014, Ren et al., 2014, Rothenberg et al., 2011, Sommella et al., 2013). Along with drinking water and seafood, the consumption of rice has become the major contributor to As and Hg, thereby causing potential health risks (Sun, Williams, & Zhu, 2009). Studies have shown a positive correlation between health risks and the total As and Hg concentrations of rice (Fang et al., 2014, Qian et al., 2010). The toxicities of As and Hg depend on their chemical speciation. Generally, inorganic As is more toxic than organic As, and the levels of toxicity of As compounds are as follows: arsenite (AsIII) > arsenate (AsV) > monomethlyarsonate (MMA) > dimethylarsinate (DMA) (Gurkan et al., 2015, Moreda-Piñeiro et al., 2011). Interestingly, some organic As species such as arsenobetaine and arsenosugars have been proved to be nontoxic (Gómez-Ariza et al., 2004, Nam et al., 2010). Evidence has shown that the major Hg species generally found in biological samples are either methylmecury (MeHg) or inorganic mercury (HgII) (Doker and Bosgelmez, 2015, Li et al., 2007). The levels of toxicity of Hg compounds are as follows: MeHg > ethylmercury (EtHg) > HgII. Therefore, measuring the total As and Hg concentration alone is not enough to assess the hazards of As and Hg.
In recent years, a number of analytical techniques have been widely employed for the speciation analysis of As or Hg, including gas chromatography (GC) or high performance liquid chromatography (HPLC) coupled with element specific techniques such as atomic absorption spectroscopy (AAS), atomic emission spectrometry (AES), atomic fluorescence spectroscopy (AFS), and inductively coupled plasma mass spectrometry (ICP-MS) (Do et al., 2001, Pasias. et al., 2013, Pelcova et al., 2015, Zmozinski et al., 2015). HPLC techniques are better suited for the separation of As or Hg due to the relatively wide compatibility of mobile phase composition and the easiness of sample preparation (Lin et al., 2008, Liu et al., 2013). ICP-MS also has the advantages of high sensitivity, wide linearity, low detection limit, and multielemental analysis (Iserte, Roig-Navarro, & Hernández, 2004). Therefore, coupling of ICP-MS with HPLC is the most widely used technique for the individual speciation of As or Hg that has been employed successfully on a number of different matrices (Khan et al., 2015, Moreno et al., 2013, Raber et al., 2012, Souza et al., 2013). C18 reversed-phase chromatography with the ion-pairing reagent tetrabutylammonium hydroxide (TBAH) has been employed in the separation of four selenium and four As species within 18 min by HPLC coupled with ICP-MS (Afton et al., 2008). Currently, however, a single method for the simultaneous separation of common As and Hg species in one chromatographic run has not yet been reported. Gómez-Ariza et al. (2004) established a method for the simultaneous determination of Hg and As species in natural freshwater by HPLC (hydrides generation and cold vapor) coupled with a home modified AFS and a standard AFS system. However the use of modified AFS makes this method somewhat complex, and it cannot be widely used for other matrices. To the best of our knowledge, no information is available regarding the simultaneous speciation analysis of As and Hg in rice using HPLC–ICP-MS.
The main objective of this work was to develop a method for the simultaneous speciation analysis of As and Hg species using HPLC–ICP-MS. Seven common environmentally and biologically observed As and Hg species standards were baseline separated on a C18 chromatography column via ion-pairing reversed phase chromatography. To illustrate the potential applicability of the proposed method, we successfully optimized the chromatographic method applied to the certified reference materials (CRMs) NIST 1568a rice flour, GBW 10043 rice flour, and two kinds of rice flour from local markets.
Section snippets
Reagents and materials
All the solutions were prepared with doubly deionized water (DDW) (18 MΩ cm−1, Millipore-Q American). The following commercial products were used: Nitric acid (65%) was purchased from Merck, methanol (HPLC grade) was obtained from Kermel, ammonium dihydrogen phosphate (GR) was purchased from Simopharm Chemical Reagent Co., Ltd, l-cysteine (Reagent Grade) from Solarbio Science & Technology Co., Ltd, and both ammonium acetate (GR) and tetrabutylammonium hydroxide (TBAH) 40% in water
Optimization of chromatographic separation conditions
Previous studies showed that pH 5.5–6.5 was optimal for As species and successfully separation of As species was achieved at pH 6.0 on a C18 column with ion-pairing reagent (Afton et al., 2008). Therefore, according to previous publications (Afton et al., 2008, Li et al., 2007), a preliminary study was attempted to select the mobile phase at pH 6.0 using Agilent Eclipse plus C18 column without using any ion-pairing reagents (mobile A, 15 mmol/L NH4H2PO4 for As; mobile phase B, 3% (v/v) methanol,
Conclusions
In this study, an analytical technique for simultaneous speciation of As and Hg in rice flour by HPLC-ICP-MS was established, and 1% HNO3 microwave-assisted extraction was chosen as the simultaneous extraction for As and Hg species in rice flour. All As and Hg species could be separated within 20 min (including 10 min re-equilibration time) by using TBAH as the ion-pairing reagent on a C18 column. The approach is simple and sensitive and can be used for the simultaneous speciation analysis of As
Conflict of Interest
The authors declare that they have no conflict of interest.
Acknowledgements
This work was supported by the National Natural Science Foundation of China (31471680), the China Special Fund for Grain-scientific Research in the Public Interest (201313007), and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).
References (40)
- et al.
Simultaneous characterization of selenium and arsenic analytes via ion-pairing reversed phase chromatography with inductively coupled plasma and electrospray ionization ion trap mass spectrometry for detection applications to river water, plant extract and urine matrices
Journal of Chromatography A
(2008) - et al.
Mercury speciation in seafood samples by LC-ICP-MS with a rapid ultrasound-assisted extraction procedure: application to the determination of mercury in Brazilian seafood samples
Food Chemistry
(2011) - et al.
Speciation of arsenic in rice and estimation of daily intake of different arsenic species by brazilians through rice consumption
Journal of Hazardous Materials
(2011) - et al.
Speciation analysis of mercury and lead in fish samples using liquid chromatography-inductively coupled plasma mass spectrometry
Journal of Chromatography A
(2007) - et al.
Speciation of arsenic and selenium compounds by ion-pair reversed-phase chromatogrphy with electrothermic atomic absorption spectrometry application of experimental design for chromatographic optimisation
Journal of Chromatography A
(2001) - et al.
Rapid extraction and reverse phase-liquid chromatographic separation of mercury(II) and methylmercury in fish samples with inductively coupled plasma mass spectrometric detection applying oxygen addition into plasma
Food Chemistry
(2015) - et al.
Concentrations and health risks of lead, cadmium, arsenic, and mercury in rice and edible mushrooms in China
Food Chemistry
(2014) - et al.
Simultaneous determination of mercury and arsenic species in natural freshwater by liquid chromatography with on-line UV irradiation, generation of hydrides and cold vapor and tandem atomic fluorescence detection
Journal of Chromatography A
(2004) - et al.
Development of a simple, sensitive and inexpensive ion-pairing cloud point extraction approach for the determination of trace inorganic arsenic species in spring water, beverage and rice samples by UV-Vis spectrophotometry
Food Chemistry
(2015) - et al.
Ion-pair reversed phase liquid chromatography with ultraviolet detection for analysis of ultraviolet transparent cations
Journal of Chromatography A
(2015)
Determination of toxic heavy metals and speciation of arsenic in seaweeds from South Korea
Food Chemistry
Extraction and detection of organoarsenic feed additives and common arsenic species in environmental matrices by HPLC–ICP-MS
Microchemical Journal
Approach for rapid extraction and speciation of mercury using a microtip ultrasonic probe followed by LC-ICP-MS
Talanta
Impact of agronomic practices on arsenic accumulation and speciation in rice grain
Environmental Pollution
Extraction and speciation of arsenic in plants grown on arsenic contaminated soils
Talanta
In-vivo and in-vitro testing to assess the bioaccessibility and the bioavailability of arsenic, selenium and mercury species in food samples
Trends in Analytical Chemistry
Simultaneous speciation and preconcentration of ultra trace concentrations of mercury and selenium species in environmental and biological samples by hollow fiber liquid phase microextraction prior to high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry
Journal of Chromatography A
A study on the extraction and quantitation of total arsenic and arsenic species in seafood by HPLC-ICP-MS
Microchemical Journal
The extraction and speciation of arsenic in rice flour by HPLC-ICP-MS
Talanta
Extraction techniques for arsenic species in rice flour and their speciation by HPLC-ICP-MS
Talanta
Cited by (63)
A self-amplifying plasmid based ultrasensitive biosensor for the detection of As(Ⅲ) in water
2023, Biosensors and BioelectronicsFabrication of novel copper MOF nanoparticles for nanozymatic detection of mercury ions
2023, Journal of Materials Research and TechnologySwitching on-off-on colorimetric sensor based on Fe-N/S-C single-atom nanozyme for ultrasensitive and multimodal detection of Hg<sup>2+</sup>
2022, Science of the Total EnvironmentMercury(II) stripping electroanalysis with hot microelectrodes
2022, Electrochimica ActaRational engineering of Ag-doped reduced graphene oxide as electrochemical sensor for trace mercury ions monitoring
2021, Sensors and Actuators, B: ChemicalCitation Excerpt :The core safeguard of supervision comes from the powerful innovation and continuous progress of monitoring technology. Up to now, various analytical methods have been reported for detection of Hg2+, such as inductive coupled plasma mass spectrometry (ICP-MS) [4], cold-vapor atomic absorption spectroscopy (CVAAS) [5], UV–vis spectrophotometry [6], X-ray fluorescence spectrometry (XFS) [7], atomic absorption spectrometry (AAS) [8], gas chromatography (GC) [9], atomic fluorescence spectrometry (AFS) [10], atomic emission spectrometry (AES) [11], electrochemical biosensing [12,13], field-effect transistor (FET) [14], localized surface plasmon resonance (LSPR) [15], colorimetry [16], etc. Among these methods, electrochemical methods exhibit outstanding advantages including low price, rapid response, high sensitivity, superior anti-interference, and easy on-site operation features [17–19].