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Simultaneous speciation analysis of inorganic arsenic and methylmercury in edible fish oil by high-performance liquid chromatography–inductively coupled plasma mass spectrometry


Arsenic (As) and mercury (Hg) are typical contaminants in foodstuffs of marine origin, and their toxicities vary greatly depending on the chemical form being present. Valuable risk assessment with respect to these contaminants in food items requires information based on theirs toxicities and bioavailabilities and therefore calls for speciation analysis. Unfortunately, while speciation analysis offers much higher information value than simple trace element analysis, that comes with higher costs. The higher costs are resulting from the higher investment in more sophisticated instrumentation, more complex sample preparation and lower sample throughput. Typically, methods for speciation analysis are dedicated to the species of a single element, since the conditions for sample preparation, species separation and detection call for the optimization of many different parameters not easy to achieve for different element species under identical conditions.
The new study:
In order to improve the situation for the determination of As and Hg species in edible oils, a group of Japanese researchers now developed a method for the simultaneous extraction and speciation analysis.  Extraction conditions were evaluated with respect to efficiency and species stability. Water, HNO3 and TMAH were tested as extractants under different conditions.  As a result of optimization, oil samples were treated with an aqueous TMAH solution at 80°C for 1 h. After centrifugation, an aliquot of the aqueous phase was separated and L-cystein was added before analysis by HPLC-ICP-MS.

HPLC conditions were also optimized with respect to mobile phase composition and pH, resulting un conditions for simultaneous speciation of iAs and MeHG in the pH range of 2.3 to 3.0. The optimum eluent composition consisted of 5 mM sodium 1-butanesulfonate, 2 mM NH4H2PO4, 4 mM TMAH, 5 mM L-cysteine, and 0.1 % methanol (pH 2.3) for the simultaneous separation of As and Hg species. Under these conditions EtHG and phenHg eluted vary late at approximately 1500 and 2100 s, respectively. Since their presence in fish oil can be expected only for contaminated samples, the measurement time for simultaneous speciation of iAs and MeHg was set to 900 s (15 min) in this study.  

The proposed measurement procedure was then validated by analysing several Japanese CRMs, showing good recoveries for iAs, DMA, AsB, total As, iHg MeHg and total Hg. When the simultaneous speciation was carried out for several kinds of edible oil, the concentration ranges of iAs and MeHg were 0.001 mg kg-1 to 0.010 mg kg-1 and 1.21 ng g-1 to 10.18 ng g-1, respectively.

The original publication:

T. Narukawa, T. Iwai, K. Chiba, Simultaneous speciation analysis of inorganic arsenic and methylmercury in edible oil by high-performance liquid chromatography–inductively coupled plasma mass spectrometry, Talanta, 210 (2020) 120646. DOI: 10.1016/j.talanta.2019.120646

Used techniques and instrumentation:

Related studies

Danyu Zhang, Shiwei Yang, Qingfang Ma, Jiannan Sun, Heyong Cheng, Yuanchao Wang, Jinhua Liu, Simultaneous multi-elemental speciation of As, Hg and Pb by inductively coupled plasma mass spectrometry interfaced with high-performance liquid chromatography, Food Chemistry 313 (2020) 126119. DOI: 10.1016/j.foodchem.2019.126119

Danyu Zhang, Shiwei Yanga, Heyong Chenga, Yuanchao Wang, Jinhua Liu, Speciation of inorganic and organic species of mercury and arsenic in lotus root using high performance liquid chromatography with inductively coupled plasma mass spectrometric detection in one run, Talanta, 199 (2019) 620-627. DOI: 10.1016/j.talanta.2019.03.023

Cheng-Hung Yao, Shiuj-Jen Jiang, A.C. Sahayam, Yeou-Lih Huang, Speciation of Mercury in fish oils using liquid chromatography inductively coupled pl,asma mass spectrometry, Microchem. J., 133 (2017) 556-560. DOI: 10.1016/j.microc.2017.04.034

Monika Marcinkowska, Danuta Baralkiewicz, Multielemental speciation analysis by advanced hyphenated Technique - HPLC/ICP-MS: A review, Talanta, 161 (2016) 177-204.

Yong Fang, Yushi Pan, Peng Li, Mei Xue, Fei Pei, Wenjian Yang, Ning Ma, Qiuhui Hu, Simultaneous determination of arsenic and mercury species in rice by ion-pairing reversed phase chromatography with inductively coupled plasma mass spectrometry, Food Chem., 213 (2016) 609–615. DOI: 10.1016/j.foodchem.2016.07.003

Ute Kohlmeyer, Sandra Jakubik, Jürgen Kuballa, Eckard Jantzen, Determination  of Arsenic Species in Fish Oil After Acid Digestion, Microchim. Acta, 151/3-4 (2005) 249-255. DOI: 10.1007/s00604-005-0406-8

Stacy E Foran, James G. Flood, Kent B Lewandrowski, Measurement of Mercury Levels in Concentrated Over-The-Counter Fish Oil Preparations: Is Fish Oil Healthier Than Fish?
Arch. Pathol.Lab. Med., 127/12 (2003) 1603-1605. DOI: 10.1043/1543-2165(2003)127<1603:MOMLIC>2.0.CO;2

Related EVISA News (newest first)

January 5, 2017: ERM-AE671: A new Certified Reference Material to make methylmercury measurements in food more reliable
September 17, 2015: Arsenic species in rice: A new Australian reference material
February 10, 2015: Capabilities of EU labs to determine inorganic arsenic in food have improved
January 18, 2015: Influence of culinary treatments of fish on its mercury content and speciation
July 15, 2013: New arsenic compounds found in herring
January 14, 2013: Mercury Levels in Humans and Fish Around the World Regularly Exceed Health Advisory Levels
December 24, 2012: Mercury in food – EFSA updates advice on risks for public health
June 17, 2012: Factors Affecting Methylmercury Accumulation in the Food Chain
March 9, 2010: CEN calls for the development of standardised methods for the analysis of metal species in food
February 11, 2009: Mercury in Fish is a Global Health Concern
August 8, 2008: Arsenolipids in fish oil found by arsenic speciation analysis

last time modified: February 19, 2020

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