Achieving rapid low-pressure ion chromatography separations on short silica-based monolithic columns

Short silica-based monolithic columns (0.5-1 cm) are coated with the surfactant didodecyldimethylammonium bromide (DDAB) and used for fast ion exchange separations of small inorganic anions. Sources of extra-column band broadening are assessed and minimized to obtain separations of seven analytes (iodate, chloride, nitrate, bromide, nitrite, phosphate, sulphate) in two minutes at 2 mL/min. Eluents used are 6 and 9 mM 4-cyanophenol at pH 7.3-7.4 or 5 mM 4-hydroxybenzoic acid at pH 5.6. DDAB coating stability is improved by 15-fold by the addition of a DDAB coated pre-column before the injection valve. Separations are obtained using a low-pressure glass syringe.