2.4. Determination of Total Arsenic
Arsenic Content, Speciation, and Distribution in Wild Cordyceps sinensis
Evid Based Complement Alternat Med, Feb 19, 2021; DOI: 10.1155/2021/6651498

An ICP-MS system coupled with the microwave digestion technique was used for sample preparation and detection. C. sinensis powder, 0.25 g, was decomposed using microwave equipment with a mixture of HNO3 (4.0 mL) and H2O2 (2.0 mL). The operating program of the microwave system was as follows: the samples were heated to 120°C from room temperature in 5 min and held for 5 min, then heated to 160°C in 5 min and held for 10 min, and heated to 200°C in 15 min and held for 15 min. During the digestion process the wave power was set to 1800 W. After digestion, the samples were cooled to room temperature. Excess HNO3 was removed by heating the sample solution at 120°C for 20 min. The digestion sample solutions were cooled to room temperature and diluted with ultrapure water up to 50 mL.

The analysis conditions, including RF power, plasma gas flow, auxiliary gas flow, nebulizer gas flow, sampling depth, and peristaltic pump rate, were 1250 W, 18 L/min, 1.2 L/min, 0.72 L/min, 6 mm, and 35 r/min, respectively. Besides, selected isotope m/z 75 was detected ion. Samples were quantified with external calibration curve As standards (calibration points: 1, 5, 10, 20, and 50 ng/mL), and internal standards (40 ng/mL of 72Ge) were used for metal determination by ICP-MS. Before determination, the status of ICP-MS was adjusted to optimum with the tuning solution. The internal standard was used, and internal standard solution was introduced into the sample flow with a T shape pipe online. Triplicate analyses were performed for each sample. The corresponding digestion blanks (reagent blanks) were also measured. The arsenic of CRM GBW09588 (Atractylodes macrocephala) was determined and used for quality control purposes using the same methods.