Abstract: A system separates and in-situ analyzes a discrete sample of multiphase fluid. The system includes a separation vessel having a first inner chamber for separating a discrete sample of multiphase fluid into liquid phases including an aqueous liquid phase and a nonporous liquid phase, and a built-in water analysis unit. The built-in water analysis unit includes an analytical cell disposed inside the first inner chamber of the separation vessel, the analytical cell having a second inner chamber, and at least one probe having a sensing area disposed in the second inner chamber for in-situ analysis of a sample of the aqueous liquid phase that is separated from the discrete sample of multiphase fluid in the first inner chamber and that is channeled to the second inner chamber from the first inner chamber for the in-situ analysis. The second inner chamber is defined inside the first inner chamber.