For electroanalytical measurement of molten chloride salts, various voltammetry methods have been used on mixtures of MgCl2 and LaCl3 in eutectic LiCl-KCl. These salt mixtures are of primary interest to spent nuclear fuel electrorefining systems. MgCl2 is used as a surrogate for PuCl3, while LaCl3 represents rare earth fission product salts. Cyclic voltammetry scans with these salt mixtures exhibited extra peaks, presumably due to underpotential deposition of La(III) ions onto Mg. Quantitatively, the current contribution from each peak was best-determined using normal pulse voltammetry and fit to the Cottrell equation. This yielded linear correlations for concentration versus diffusional current with very high correlation factors. Applying this method, it was determined that concentration measurement error was less than 4% for both MgCl2 and LaCl3. (C) 2016 The Electrochemical Society. All rights reserved.