Complexation of polyvinyl acetate with iodine

Polyvinyl acetate and iodine form a characteristic red complex in the presence of potassium iodide. Spectrophotometry of the complex at 510 nm in a methanol-water system at 20 degrees yields linear calibration curves over the range 25-100 mg of polyvinyl acetate per 1. of final solution. The limit of detection is 0.1 mg of polyvinyl acetate in 0.5 ml of initial sample. Replacement of acetate groups by inert groups reduces the sensitivity of the method, and other details of the system are discussed.