A method comprises correlating—in a system which comprises a non-aqueous phase comprising a hydrocarbon fluid, and an aqueous phase—partitioning levels of a basic contaminant and/or an acid of interest into the aqueous phase with the pH of the aqueous phase. The partitioning levels of the basic contaminant and the acid of interest, as well as the pH of the aqueous phase, are obtained under conditions which are representative of those used in a partitioning process in which a basic contaminant is removed from a hydrocarbon fluid.
The correlations may be used in a method for selecting an acidic environment for use in a partitioning process, for estimating corrosion risk downstream of a partitioning process, or for controlling a partitioning process.