Size-exclusion chromatography of solubilised low-rank coal

Solubilised brown coal is a polydisperse and chemically heterogeneous polyanion. The parameters appropriate for estimation of its molecular mass (M(r)) by size-exclusion chromatography (SEC) using a stationary phase comprising glyceryl-propyl silica were investigated. Ion exclusion occurred when the ionic strength (I) was zero, being most pronounced for coal soluble at low pH. Reversed-phase partitioning appeared at low ionic strength. Non size-exclusion interactions were minimised when I was between 0 and 0.033. The estimates for the modal M(r) of solubilised coal ranged between 355000 and 33000. These values are consistent with ultrafiltration data, suggesting that SEC is a practical method for determining coal Mr.