A system is disclosed that can be used to determine concentrations of components of a multiphase fluid. The system comprises: a first flowmeter configured to receive a fluid flow and to generate one or more measurements of the fluid flow. A separation vessel receives the fluid flow, and to at least partially separate the first liquid and the second liquid. A second flowmeter is configured to receive either the second liquid or a mixture of the first liquid and the second liquid, to generate one or more measurements. A proportion of the second liquid to the first liquid in the mixture is greater than a proportion of the second liquid to the first liquid in the fluid flow. A third flowmeter is configured to receive the first liquid and to generate one or more measurements of the first liquid. A data processing apparatus is operatively coupled to the flowmeters, the data processing apparatus and is configured to perform various operations.