Remove high levels of alkaline earth and transition metals from sample matrices without acidifying the sample. Thermo Scientific™ Dionex™ OnGuard™ II Na Cartridges are an off-line sample preparation technique that uses 16% cross-linked, styrene-based, sulfonic acid resin in the sodium form to eliminate these matrix interferences to improve IC performance and facilitate low-level ion analysis. Use them singly or in series, or pretreat up to 12 samples in parallel using the optional Dionex OnGuard Sample Prep Station.