The concentrations of arsenic species in CHMs samples collected directly from fields are shown in Table 2. Only AsIII and AsV were detected in the extract solutions of CHMs with the roots as medicines. The concentrations ranged at 47.2e182 ng/g for AsIII and at
1.1e264 ng/g for AsV. Arsenite was the predominant species in the extracts of 63% samples, accounting for 60e99% of total As. Arsenate was the main species in the remainder samples with the proportion at 66e74% (Table 2). There was quite a big difference in the dominant As species in the medicines from fields, which might depend on the growing conditions and their genetic properties.