*3.3. Measurement of Se Content in SeCS*

The selenium content of SeCS was measured using 7500 CX ICP-MS (Agilent, Palo Alto, CA, USA). The following measurement conditions of the instrument: incident power of 1550 W; plasma gas flow rate at 15 L/min; carrier gas flow rate at 1.0 L/min; auxiliary gas flow rate at 1.0 L/min; helium flow rate at 4.0 mL/min; atomization chamber temperature of 2 ◦C; sampling depth of 10.0 mm; sampling rate at 1.0 L/min.
