Detection of inorganic arsenic in rice using a field test kit: a screening ...
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 Brown rice Organic Brown rice Easy cook Brown rice Brown Rice Long grain rice (Savers) Long grain rice Long grain rice (easy cook) Long grain rice easy cook (bio) Long Grain Basmati Basmati Basmati Aptimil Boots Cow and Gate Heinz Hipp Organics Holle Organix White Rice Pudding Rice Risotto Paella Thai Jasmine Japanese Rice paper Long Grain Paella Rice Noodles Rice Flour
sample ID S-1 S-2 S-3 S-4 S-5 S-6 S-7 S-8
Shop Sainsbury’s The co-operative Tesco Tesco Morrison Shop in Kazakhstan Rice 'n' Spice Sainsbury’s
country of Origin Unknown Italy Unknown Various Unknown Kazakhstan Unknown Unknown
S-9 S-10 S-11 S-12 S-13 S-14 S-15 S-16 S-17 S-18 S-19 S-20 S-21 S-22 S-23 S-24 S-25 S-26 S-27 S-28 S-29 S-30
Morrison's Tesco Spar Sainsbury's Boots Boots Boots Boots Boots Boots Boots Sainsbury's Sainsbury's Tesco Morrison's Co-operative Matthew's Foods Twin Dragon Co-operative Co-operative Long Kow Global
Various India India/Pakistan India
India Unknown Italy Unknown Thai Land Japan? Vietnam? Various Spain Taiwan 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 P1 P2 P3 P4 P5
Mean iAs (ng/g) 141 142 150 145 142
SD 18 23 20 25 15
RSD(%) 13 16 13 17 10
Error % -1.4 -0.7 +4.9 +1.4 -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
% RSD
35 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
Intensity (CPS)
12000
2
10000 8000 6000
3
1
4000
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 Field test kit A Field test kit B
iAs in rice (ng/g)
200
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).
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 Brown rice Organic Brown rice Easy cook Brown rice Brown Rice Long grain rice (Savers) Long grain rice Long grain rice (easy cook) Long grain rice easy cook (bio) Long Grain Basmati Basmati Basmati Aptimil Boots Cow and Gate Heinz Hipp Organics Holle Organix White Rice Pudding Rice Risotto Paella Thai Jasmine Japanese Rice paper Long Grain Paella Rice Noodles Rice Flour
sample ID S-1 S-2 S-3 S-4 S-5 S-6 S-7 S-8
Shop Sainsbury’s The co-operative Tesco Tesco Morrison Shop in Kazakhstan Rice 'n' Spice Sainsbury’s
country of Origin Unknown Italy Unknown Various Unknown Kazakhstan Unknown Unknown
S-9 S-10 S-11 S-12 S-13 S-14 S-15 S-16 S-17 S-18 S-19 S-20 S-21 S-22 S-23 S-24 S-25 S-26 S-27 S-28 S-29 S-30
Morrison's Tesco Spar Sainsbury's Boots Boots Boots Boots Boots Boots Boots Sainsbury's Sainsbury's Tesco Morrison's Co-operative Matthew's Foods Twin Dragon Co-operative Co-operative Long Kow Global
Various India India/Pakistan India
India Unknown Italy Unknown Thai Land Japan? Vietnam? Various Spain Taiwan 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 P1 P2 P3 P4 P5
Mean iAs (ng/g) 141 142 150 145 142
SD 18 23 20 25 15
RSD(%) 13 16 13 17 10
Error % -1.4 -0.7 +4.9 +1.4 -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
% RSD
35 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
Intensity (CPS)
12000
2
10000 8000 6000
3
1
4000
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 Field test kit A Field test kit B
iAs in rice (ng/g)
200
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).
