Abstract: A model system with blue dextran, potassium hexacyanoferrate(III) and heparin as analytes was used to generate second-order FIA data. The system incorporated a gel-filtration column (2.5 cm x 16 mm i.d.) packed with Sephadex G-25 Superfine. Photodiode array detection was at 220-594 nm with scanning at 1 s intervals for 75 s, starting 20 s after injection. The tri-linear parallel factor analysis (PARAFAC) algorithm (Smilde et al., J. Chemom., 1994, 8, 21) c ombined with multiple linear regression and tri-linear partial least-squares regression (tri-PLS; Bro, Ibid., 1996, 10, 47) were used for data processing. The prediction abilities of the two methods were satisfactory for two-component mixtures and the detection of unknown interferents. The tri-PLS method was slightly better.