A system and method for estimating a concentration of monoethanolamine (MEA) in a fluid. A substrate for supporting a sample of the fluid during testing includes a carbon nanotube mat layer, a silver nanowire layer disposed on the carbon nanotube mat layer, and a chemical enhancer layer disposed on the silver nanowire layer. A sample of the fluid is placed on the substrate, and the fluid sample is radiated with electromagnetic radiation at a selected energy level. A detector measures a Raman spectrum emitted from the sample in response to the electromagnetic radiation. A processor estimates the concentration of MEA in the sample from the Raman spectrum and adds a corrosion inhibitor to the fluid in an amount based on the estimated concentration of MEA to reduce the concentration of MEA in the fluid.