Potential effects of surface water components on actinide determinations conducted by ion chromatography

An elution program for separating actinides (thorium, uranium, neptunium, plutonium, americium, and curium) on low hydrophobicity ion exchange columns was evaluated for solutions spiked with actinides and common surface water components. Potential interferences from dissolved ions (Na+, K+, Ca2+, Cl-, and SO(4)2-), humic acid, and radium were investigated. Sulfate levels greater than 0.25 mumol interfered with separation of americium, curium, and plutonium. Humic acid levels above 100 micrograms produced distinct widening of actinide peaks and reduced actinide recoveries. These interferences limit the range of useful sample volumes and create a need for sample pretreatment procedures. No interferences were produced by 0.025 to 2.5 mumol Ca2+, 0.045 to 4.5 mumol Na+, 0.015 to 1.5 mumol K+, and 0.025 to 4.5 mumol Cl-. In the absence of interferences, the program effectively separated radium from the actinides.