Is saliva a potential biomarker of arsenic exposure? A case-control study in West Bengal, India

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1 Supporting Information for the manuscript Is saliva a potential biomarker of arsenic exposure? A case-control study in West Bengal, India Subhamoy Bhowmick 1,2, Dipti Halder 1,3, Amit kumar Kundu 1, Debasree Saha 1, Mònica Iglesias 2, Jerome Nriagu 4, Debendra Nath Guha Mazumder 5, Gabriela Roman-Ross 6, Debashis Chatterjee 1 * 1 Department of Chemistry, University of Kalyani, Nadia , West Bengal, India 2 Department of Chemistry, University of Girona, Campus Montilivi, Girona, Spain 3 KTH-International Groundwater Arsenic Research Group, Royal Institute of Technology, SE Stockholm, Sweden 4 Department of Environmental Health Sciences, School of Public Health, University of Michigan, 109 Observatory Street, Ann Arbor, MI , USA 5 DNGM Research Foundation, 37C Block B, New Alipore, Kolkata , India 6 AMPHOS 21 Consulting S.L. Passeig de Garcia i Faria 49-51, Barcelona, Spain. *Contact and corresponding author: Debashis Chatterjee (phone: ; fax: ; dbchat2001@rediffmail.com) CONTENT Page number Item Caption Text S1 S5 Text S2 References S2 Figure S1 Details of the effect of alcohol and internal standard on As measurement in spiked non-contaminated saliva samples Distribution of As concentration in drinking water, urine and saliva of participants involved in the study S4 Figure S2 Figure Percentage recovery of As from spiked saliva samples. Error bar represents standard deviation (SD). (a) Effect of ethanol on the sensitivity of As measurement in ICP- MS and (b) effect of internal standard (Rh and Y) for measurement of As in ICP-MS. S1

2 Figure S1. Distribution of As concentration in drinking water, urine and saliva of participants involved in the study S2

3 Figure S2. Percentage recovery of As from spiked saliva samples. Error bar represents standard deviation (SD). Text. Details of the effect of alcohol and internal standard on As measurement in spiked non-contaminated saliva samples The effect of alcohol and internal standard on As measurement of spiked saliva samples in ICP-MS was evaluated. The sensitivity of As measurement increased on addition of 2 % ethanol (EtOH) as evidenced from the increase in slope of the curve (Figure a). The increase in As signal owing to addition of small amount of alcohol (2 % EtOH) is due to charge transfer reaction between positively charged carbon and 75 As in the plasma. 1-3 However, addition of excess alcohol may cause local cooling in the centre of the plasma and a reduction of analyte signal can take place. 1 Additionally, effect of various internal standards (IS) was also evaluated to minimize, if necessary, possible matrix effects and/or instrumental drift. Rhodium (Rh) and Yttrium (Y) are some of the most commonly used IS for ICP-MS and their masses are not so different from that of the As. Although their ionization potential is quite lower in comparison

4 with that of the As, they had showed good behaviour in previous studies. 3 Figure b shows the curve of CPS (counts per second) of As (normalized with IS) against the concentration of spiked As. It was found that although Y had a higher CPS ratio than Rh but the linearity was poor even at higher concentration of As in the spiked samples. In comparison, Rh had a better sensitivity for As measurement in our spiked saliva sample than Y and therefore Rh was used as an internal standard for measurement of all saliva samples. Figure. (a) Effect of ethanol on the sensitivity of As measurement in ICP-MS and (b) effect of internal standard (Rh and Y) for measurement of As in ICP-MS. S4

5 Text S2. References (1) Allain, P.; Jaunault, L.; Mauras, Y.; Mermet, J. M.; Delaporte, T. Signal enhancement of element due to the presence of carbon-containing compound in inductively coupled plasma mass spectrometry. Anal. Chem. 1991, 63, (2) Larsen, E. H.; Stürup, S. Carbon enhanced inductively coupled plasma mass spectrometric detection of arsenic and selenium and its application to arsenic speciation. J. Anal. Atom. Spectrom. 1994, 9, (3) Colon, M.; Hidalgo, M.; Iglesias, M. Arsenic determination by ICP-QMS with octopole collision/reaction cell. Overcome of matrix effects under vented and pressurized cell conditions. Talanta, 2011, 85, S5