Abstract: A method, system, and apparatus are described for evaluating the constituents of a heat exchange fluid having acid-based corrosion inhibitors therein, such as organic acid-based corrosion inhibitors. The method provides for obtaining a sample of the heat exchange fluid and then acidifying the sample to reduce the solubility of target acid-based corrosion inhibitors therein. This may be done, for example by adding an acid or acid buffer to the sample. The target acid-based corrosion inhibitors are then separated from the acidified sample. For example, the acidified sample may be passed through a solid phase extraction device to separate the target acid-based corrosion inhibitors from the sample. The separated acid-based corrosion inhibitors are then evaluated, thereby obtaining an indication of the concentration of acid-based corrosion inhibitors in the subject heat exchange fluid.