Size exclusion chromatography (SEC) equipped with light scattering (LS) and refractive index (RI) detectors was employed to determine the compositions of complicated binary mixtures.The principle of absolute quantification of size exclusion chromatography was deduced for LS and RI detectors according to signals of both detectors and the injected mass.It is founded that the response factor of RI detector is only decided by the refractive index increment () of the injected sample

while the response factor of LS detector is determined by both and the weight average molar mass (Mw) of the sample.By a theoretical analysis we conclude that the response factors of both LS and RI detectors are linear functions with the composition of a binary polymer blend.Six pairs of binary mixtures with weak interactive effect were employed to test the linear relationship.The experimental results show an excellent accordance with the theory.At last

the linear relationships between the response factors and the composition was utilized for the compositional analysis of binary mixtures.With a careful analysis

it is discovered that the compositions determined by LS detector are more accurate than the ones by RI detector in some cases.For RI detector

seven error points are out of the range from -10% to 10%

while only two error points are out of this range for LS detector.Specially

four bad points for RI detector are much more than one point for LS detector for the case at the low composition W =10%.For another case in the mixture of two kinds of polystyrene

the number of bad points for RI detector reaches four in the five compositions while none yields for LS detector.This SEC-LS method is effective for the compositional analysis of binary mixtures and can be derived to more complicated industrial mixtures.