Mercury determination was carried out by cold vapor atomic absorption spectrometry
(CVAAS), using sodium tetrahydroborate as reducing agent and hydrochloric
acid as carrier solution. About 500 lL of the each stock sample solution of
CRM, and real samples were transferred to the PTFE flasks of the MHS-15 system
and 10 mL of a 0.15 M HCl solution were added, along with 40 lL of the antifoam
agent. The system was sealed and 3% (m/v) NaBH4 was added for 5s to the PTFE
flask. A stream of high purity argon gas at a flow rate of 200 mL/min carried the
Hg vapor generated in system to the quartz cell, and the signals of the generated
Hg atoms were measured. Calibration was performed using aqueous standards
(1–25 lg/L) and subjected to CV AAS procedure described above. The validity and
efficiency of the microwave assisted digestion method was checked with certified
values of CRM DORM -2, as reported in our previous work