Abstract Ab in situ, non-destructive method for the analysis of heavy metal fluoride melts by electrochemical means has been developed. The technique involves differential pulse voltammetry at a rotating carbon disc electrode. The electrode is swept cathodically in the melt at 600°C at a fixed rate to a potential beyond the deposition potentials of the analytic ions and then swept in the reverse direction. During the cathodization process, various transition metal ions including copper, iron, nickel and cobalt are reduced from the melt onto the electrode. Previous studies have shown that the main ZBLAN melt cations are all more stable against reduction than these problematic contaminating ions. In the anodic sweep the ions reduced onto the surface of the electrode are oxidized off and the resultant current is monitored. Spiking the melt with known amounts of the contaminant allows the construction of a calibration curve. Typical analytical sensitivity is found to be at least 100 ppb in each of copper, iron, nickel and cobalt. The technique shows separate peaks for copper, iron and nickel. Cobalt lies close to nickel such that quantitative separation is not possible. Differential pulse anodic stripping voltammetry has also been used in this work. This technique was found to produce peak currents that were too large to be easily measurable using our equipment. This suggests that analytical sensitivity of 10 ppb or less may be possible.