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9:3 Contamina5on from Reagents

High purity water:

• High purity water should be used ASAP. • "Stored" high purity water may pick up impuri;es from the storage container. • Popular storage containers are made from quartz, polyethylene (both high and low density), and fluoropolymers.

9:4 Contamina5on from Reagents

High purity water: Storage in quartz

• Quartz (fused quartz or vitreous silica) typically contains 98.8% SiO2, and impurities consisting mainly of Na2O, Al2O3, Fe2O3, MgO, and TiO2. • Quartz has a solubility in water of 11 ppm. 1 • We have measured a solubility of quartz in conductivity water of 11.2 ppm as silicic acid (equilibration time is ~4 weeks using 400 mesh quartz powder).

1. Ralph K. Iler, The Chemistry of Silica, John Wiley & Sons: New York, (1979).