【讨论】MgCl2在测试Cr6+中抑制Cr3+转化成Cr6+的机理是甚么？

希望说的详细一点！

For waste materials or soils containing soluble Cr(III) concentrations greater than four times the laboratory Cr(VI) reporting limit, Cr(VI) results obtained using this method may be biased high due to method-induced oxidation. The addition of Mg2+ in a phosphate buffer to the alkaline extraction solution has been shown to suppress this oxidation. If an analytical method for Cr(VI) is used that can correct for possible method induced oxidation/reduction, then the Mg2+ addition is optional.

from Method 3060A (PDF)
Alkaline Digestion for Hexavalent Chromium