The partitioning behavior of corrosion inhibitor (CI) among different phases is a critical factor for successful application on carbon steel. Unreliable measurement of CI residuals can lead to inaccurate dosing, overtreatment, and higher operating costs. However, obtaining a reliable and accurate measurement of CI residuals can be problematic for both operators and CI suppliers. Traditional residual techniques usually involve complicated and tedious analytical procedures. These procedures may require dedicated benchtop instruments, which utilize a centralized laboratory to perform the analysis. Recently, a novel residual technique was developed based on a proprietary nanotechnology-based spectroscopy technique. The new technique involves a handheld instrument and allows rapid and accurate measurement of CI residuals in the water phase. In the current laboratory study, this technique was applied to build a model of the partitioning of a water-soluble CI between the oil and water phases at different water cuts. It was found that the CI partitioned in the water phase preferentially in all water cuts. A higher amount of CI partitioned in the water phase with decreasing water cut. The result of the study was a CI partitioning model to be used as guidance for CI dosage in the field.