A kit and method for monitoring for the presence of catalyst fines in heavy fuel oil (HFO), including: a) providing a sample of HFO; b) mixing the HFO sample with a diluent composition comprising a non-polar solvent and with an aqueous reagent composition to provide a test sample, wherein the aqueous reagent composition comprises at least one water soluble inorganic salt and at least one water soluble base; c) allowing phase separation to occur in the test sample to provide an aqueous phase and an organic phase; and d) inspecting the aqueous phase of the test sample for the presence of catalyst fines. The diluent composition can consist of a non-polar solvent selected from mineral spirits, kerosene, naphtha, and heavy distillate and a phase transfer agent selected from tripropylene glycol monomethyl ether, ethylene glycol, propyl alcohol, isopropyl alcohol and butanol.