Method screening: to obtain the suitable extraction method of arsenic speciation
in CHMs, four methods to extract As species were evaluated in this study
according to TFA extraction method from Heitkemper et al. (2001) and microwave
extraction with 1% HNO3 solution in Zhu et al. (2008). No certified reference material
(CRM) for arsenic speciation in herbal medicine, the CRM of Chinese rice flour
GBW10010, arsenic speciation published in Zhu et al. (2008), was used to validate
analysis. We consider that the herbal medicine is normally roots or shoots different
fromrice flour, so Panax notoginseng (Sanqi in Chinese), one of herbal medicines,was
run for arsenic speciation extraction with rice CRM. Arsenic speciation in rice flour
CRM and herbal medicine sample Panax notoginseng were extracted by the following
methods: