Improving accuracy in fluoride salt composition analysis: A focus on sample preparation for ICP-MS

• Sampling methods strongly affect ICP-MS analysis of molten salts. • Complete dissolution of salts depends on acid digestion process. • Caution should be taken when comparing ICP-MS data in literature. Molten salts are versatile candidates for heat transfer/storage due to attractive thermophysical, thermochemical, and radiochemical properties. Salt impurities are a key factor in these properties, affecting corrosion of salt-facing materials and activation in nuclear applications. Inductively coupled plasma mass spectrometry (ICP-MS) can be used to measure metallic impurities in salts to high precision. However, there is no universally accepted method for ICP-MS analysis of salt impurities comparable to well-established methodologies for metals. In this paper, we present how ICP-MS analysis of (LiF) 0.465 -(NaF) 0.115 -(KF) 0.42 (FLiNaK) depends heavily on each step of sample preparation. Different sampling methods, salt particle sizes, dissolving acid concentrations, digestion methods, and microwave digestion conditions are explored. The optimal experimental condition for each is discussed with insights on safety, time management, and unit choice for seamless communication, and verified by measuring intentionally added metallic impurities (MnF 2 , NiF 2 , CoF 2 , FeF 2 ). This study presents a repeatable method for conducting accurate ICP-MS measurements on salt to yield more consistent and comparable data.