Abstract: Two flow injection systems were used in this study: (i), a common FIA manifold in which 100 µL of sample solution was injected into a water carrier stream (0.7 ml/min); and (ii), a reverse FIA manifold in which the analyte solution was the carrier stream (0.7 ml/min) and 100 µL of water was injected. Both systems were equipped with a RI detector operated at 410 nm. The dynamic range of the assay was 0-5% glycol (i.e., ethylene glycol or propylene glycol) in aqueous solution and the detection limit was 0.05%. The method was applied to the analysis of aircraft deicing/anti-icing fluids. The method was validated by standard addition experiments and by using an alternative assay method (NIR spectrometry).