Monolithic ODS-silica gel column for determination of hydrogen, sodium, ammonium and potassium in acid rain by lon chromatography

Summary A monolithic ODS-silica gel column modified by saturating it with lithium dodecylsulfate (Li-DS) was firstly used to separate monovalent cations simultaneously including H⁺, Na⁺, NH₄ ⁺ and K⁺ by ion-chromatography (IC). Using an acidified 60 mM LiCl solution (pH 3.95, containing 0.10 mM Li-DS) as eluent, these monovalent cations were separated well in the order of Na⁺<NH₄ ⁺<K⁺<H⁺ within 3 min at a flow rate of 2.0 mL min⁻¹. The detection limits of these cations by this method with conductivity detection were 20.0 μM for Na⁺, 12.0 μM for NH₄ ⁺, 9.84 μM for K⁺ and 6.20 μM for H⁺. Acid rain water samples with a pH value less than 5.00 could be analyzed directly with this IC system.