Interference of lithium in measuring magnesium by complexometry: Discussions of the mechanism

Abstract

There is usually a large concentration of magnesium in the brine of salt lakes and as a consequence it is difficult to measure Mg2+ accurately with the complexometric titration by ethylenediaminetetraacetic acid disodium salt (EDTA) because of the large levels of Li+ also coexisting in brine samples. In this study, a relationship between the relative error related to the number of drops of the indicator and the NMR spectra of anhydrous ethanol and n-butanol, with or without LiCl, was analyzed and compared. It was then possible to suggest a mechanism to explain the interference of Li+ when measuring Mg2+ and to control the interference in the alcohol mixture because Li+ can then complex with the alcohols and mainly form a complex with n-butanol. © 2013 Jie Gao et al.