SURFACE MODIFICATION OF POROUS GRAPHITE FOR ION-EXCHANGE CHROMATOGRAPHY

Three distinct types of weak anion exchanger have been prepared by ads orption of polyethyleneimine (PEI) on to porous graphite (PGC): PGC co ated dynamically with PEI, PGC coated with. an insoluble monolayer of PEI, and PGC coated with a cross-linked polymeric PEI. Using model sol utes iodate, bromide, nitrate and nitrite, dissolved in aqueous buffer s, the modified PGC's show typical ion exchange behaviour, and give ch romatographic performance similar to that of bonded ion-exchange silic a gels. Retention is reduced by increasing the ionic strength of the b uffer, and by increasing the pH. A mechanism to explain the observed t rends is presented.