Detection of inorganic arsenic in rice using a field test kit: a screening method Edi Bralatei, Severine Lacan, Eva M Krupp and Jörg Feldmann * TESLA (Trace Element Speciation Laboratory), Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen, AB24 3UE, Scotland, UK Supplementary material SI table S1: Table showing rice type/brand, local shop and country of origin. S-13 to S-19 are rice based baby food. SI table S2: Reproducibility of the field kit using the graduating spoon by five individuals analysing rice sample S-7 Figure A1: The influence of DMA in the extract on the determination of ias in rice using the field kit. Figure A2-4 show error correlations to total As, ias and DMA Figure A5 shows the concentrations of ias in the 30 samples analysed relative to the EC guidelines for polished white rice and baby rice. Figure A6 shows possible As species present in rice samples after separation on an anion exchange column. Figure A7 shows the reproducibility of two different arsenator models.
Table S1: rice sample information Rice Type/Brand sample ID Shop country of Origin Brown rice S-1 Sainsbury s Unknown Organic Brown rice S-2 The co-operative Italy Easy cook Brown rice S-3 Tesco Unknown Brown Rice S-4 Tesco Various Long grain rice (Savers) S-5 Morrison Unknown Long grain rice S-6 Shop in Kazakhstan Kazakhstan Long grain rice (easy cook) S-7 Rice 'n' Spice Unknown Long grain rice easy cook S-8 Sainsbury s Unknown (bio) Long Grain S-9 Morrison's Various Basmati S-10 Tesco India Basmati S-11 Spar India/Pakistan Basmati S-12 Sainsbury's India Aptimil S-13 Boots Boots S-14 Boots Cow and Gate S-15 Boots Heinz S-16 Boots Hipp Organics S-17 Boots Holle S-18 Boots Organix S-19 Boots White Rice S-20 Sainsbury's India Pudding Rice S-21 Sainsbury's Unknown Risotto S-22 Tesco Italy Paella S-23 Morrison's Unknown Thai Jasmine S-24 Co-operative Thai Land Japanese S-25 Matthew's Foods Japan? Rice paper S-26 Twin Dragon Vietnam? Long Grain S-27 Co-operative Various Paella S-28 Co-operative Spain Rice Noodles S-29 Long Kow Taiwan Rice Flour S-30 Global Thailand Table S2: ias concentration measured by five individuals who were given the instructions to use the scoop and the milled rice (S-7) which was previously analysed by the first author and a result of 143 +/- 16 ng/g (n=3) was determined (see Table 1). One standard deviation is reported for (n=10). The error (%) is calculated as relative error to the initial measurement by the author using the field kit and is therefore a measure of inter-person reproducibility of using the graduated spoon and the field kit.. Individuals ID Mean ias (ng/g) SD RSD(%) Error % P1 141 18 13-1.4 P2 142 23 16-0.7 P3 150 20 13 +4.9 P4 145 25 17 +1.4 P5 142 15 10-0.7
Figure A1: The influence of DMA concentration of the determination of ias in rice using the field kit for three different rice samples with different ias concentration (seetable 1). The extracts were spiked with DMA to give 5, 100 and 300 mg As as DMA / L.
Figure A2: absolute error of the field method versus the % ias of total As in rice. The amount of DMA does not influence the result of the field method. Figure A3: absolute error of ias in rice using the field method in comparison with the reference method versus the absolute amount of ias in the rice. No influence is recorded.
50 45 40 35 % RSD 30 25 20 15 10 5 0 0 50 100 150 200 250 300 ias from field method (ng/g) Figure A4: RSD of the field method (%) versus the ias concentration in rice using the field method. Figure A5: ias in rice commodities from the UK market measured by the field method and by the reference method (HPLC-ICP-MS) relative to the 2015 EC baby rice maximum limit of 100 µg kg -1 and the WHO allowed maximum contaminant limit (MCL) and EC ML for polished and white rice of 200 µg kg -1. Boxes around the limits represents the relative standard deviation on the field method of +/- 12 %.
16000 14000 12000 2 Intensity (CPS) 10000 8000 6000 4000 1 3 4 2000 0 0 2 4 6 8 10 12 14 16 18 20 Retention time (mins) Figure A6: chromatogram showing different As species after separation on an anion exchange column. Arsenite (1), Dimethylarsinic acid (2), Monomethylarsonic acid (3) and Arsenate (4) 250 200 Field test kit A Field test kit B ias in rice (ng/g) 150 100 50 0 S-4 S-9 S-20 S-21 S-22 S-23 S-24 S-25 Figure A7: ias concentration in a sub-set of samples using two Arsenators (field test kit A and B).