In this work, a mobile phone platform for portable chemical analysis is presented. This platform is based on the use of the built-in camera for capturing the image of a single-use colorimetric chemical sensor, while a custom-developed software application processes this image for obtaining its characteristic H (hue) value, which is related to analyte concentration. This software application is optimized for mobile phone usage, thus preserving battery life and targeting reduced computation time through a customized image processing scheme including a modified monodimensional edge detection algorithm. Meanwhile, the influence of physical and chemical factors has been characterized, with results showing that the presented platform provides accurate results even when variations on distance from phone to sensor, image focusing, or image centering are induced. In the same way, factors such as indicator concentration and membrane thickness have been shown to have negligible effects on the obtained H values. The calibration and testing procedures have shown that the presented platform is able to provide a detection limit of 3.1×10−5M in a range of 3.1×10−5–0.1M with a relative standard deviation for inter-membrane reproducibility lower than 1.6% for potassium concentration determination in solution.