Analytical Sciences, Short talk
AS-023

Arsenic speciation in mice gut after chronic exposure from rice

T. Chávez-Capilla1, M. Mukherjee2, M. Coll-Crespi1, A. Mestrot3*, S. Hapfelmeier4*
1Institute of Geography, University of Bern, Switzerland, 2Institute for Infectious Diseases, University of Bern, Switzerland, 3Institute of Geography, University of Bern, 3012, Bern, Switzerland, 4Institute for Infectious Diseases, University of Bern, 3010, Bern, Switzerland

According to the World Health Organization, arsenic (As) is one of the ten pollutants of major health concern [1], with more than 200 million people worldwide being at risk of As exposure from their diet [2]. In particular, rice accumulates up to 0.4 μg g−1 of As, of which 85 – 90 % corresponds arsenous acid (AsIII) and arsenic acid (AsV); and the remaining to methylarsonic acid (MMAsV) and dimethylarsinic acid (DMAsV) [3, 4, 5]. Although all four As species are classified as carcinogens by the International Agency of Research in Cancer (IARC) [1], their specific modes of toxic action are strongly related to their metabolites once in the human body. These metabolites can include the thiolated and reduced counterparts of MMAsV and DMAsV, which are highly unstable and difficult to extract and analyse in aerobic conditions. This study aims to develop and optimise analytical methods for inductively coupled plasma-mass spectrometry (ICP-MS) and high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) to measure As concentrations and identify different As species in small complex biological matrices. We achieved LOD values ranging from 0.08 to 0.25 μg kg−1 and successfully overcame the matrix effects of high carbon content samples on the plasma stability. Additionally, we developed an extraction procedure under anaerobic conditions and optimised an As speciation method based on previously published works [6, 7, 8]. To test the method in real samples, specific pathogen free (SPF) mice were fed rice-containing chow diets at varying concentrations of inorganic and organic As species. After seven weeks of chronic As exposure, mice were euthanized and all gut contents and key organs involved in As metabolism were removed, extracted and analysed. Our results show the efficient separation and identification of ten As species including the unstable thiolated and trivalent organic arsenic species. These methods are indispensable to gain reliable insights into the microbial-mediated transformations of As from the diet in mammals.

[1] World Health Organization, Exposure to Arsenic: A Major Health Concern, 2010.
[2] Joel E. Podgorski, Syed Ali Musstjab Akber Shah Eqani, Tasawar Khanam, Rizwan Ullah, Heqing Shen and Michael Berg, Science Advances, 2017, 3(8), e1700935.
[3] Badal Kumar Mandal and Kazuo T. Suzuki, Talanta, 2002, 58(1), 201-235.
[4] Kevin Francesconi, Pure and Applied Chemistry, 2010, 82(2), 373-381.
[5] William Maher, Simon Foster, Frank Krikowa, Elizabeth Donner and Enzo Lombi, Environmental Science and Technology, 2013, 47, 5821-5827.
[6] Baowei Chen, Fenglin Cao, Chungang Yuan, Xiufen Lu, Shengwen Shen, Jin Zhou and X. Chis Le, Analytical and Bioanalytical Chemistry, 2013, 405(6), 1903-1911.
[7] Baowei Chen, Xiufen Lu, Lora L. Arnold, Samuel M. Cohen and X. Chris Le, Chemical Research in Toxicology, 2016, 29, 1480-1487.
[8] Baowei Chen, Fenglin Cao, Xiufen Lu, Shengwen Shen, Jin Zhou and X. Chis Le, Talanta, 2018, 1(184):446-451.