Interference from Soluble Iron on Mercury Determination in Water by Cold Vapor Atomic Absorption Spectrometry (CV-AAS) with Sodium Borohydride as Reductant

This study demonstrated the signal enhancement interference from soluble iron (Fe) during mercury (Hg) determination in water by cold vapor atomic absorption spectrometry (CV-AAS) using sodium borohydride (NaBH4) as reductant. In the presence of 50 mg L-1 soluble Fe, Hg values will be overestimated by around 25%. The reason for the Hg signal enhancement is still unclear, but it is speculated to be attributable to the catalyst function for the equilibrium reduction reaction between Hg2+ and BH4- from the atomic Fe formed at the same time. Using the matrix matching calibration standards prepared in 50 mg L-1 Fe solution, the problem of Hg overestimation could be minimized. This study also indicated that stannous chloride (SnCl2), another common reductant for Hg analysis, does not suffer from the overestimation problem from soluble Fe in the presence of NaBH4.

Automated summary

This study demonstrated that soluble iron can lead to overestimation of mercury values during analysis using CV-AAS, but the issue can be minimized by using matrix-matching calibration standards prepared in 50 mg L-1 iron solution. It was also found that stannous chloride is not affected by soluble iron in the presence of NaBH4.