PROBLEMS IN THE SIZE-EXCLUSION CHROMATOGRAPHY OF CELLULOSE NITRATES - NONEXCLUSION EFFECTS AND UNIVERSAL CALIBRATION

It is shown that cellulose nitrates (CN) (degree of substitution from 2.1 to 2.97) in pure tetrahydrofuran (THF) during size-exclusion chromatography (SEC) on silanized silica gel exibit polyelectrolytic properties and their behaviour is complicated by several non-exclusion effects. Substitution heterogeneity and ionogenic groups affect the properties of CN solutions and their SEC behaviour. Addition of 0.01 mol/l of acetic acid to the eluent suppresses the non-exclusion effects and leads to validity of a universal calibration between CN and polystyrene. The Mark-Houwink equation parameters for CN in THF-0.01 mol/l acetic acid were calculated to be α = 0.73 and K = 6.44 · 10-4 dl/g. © 1990.