Applied Microspheres’ Zeta Potential Controls consist of negatively charged polystyrene particle suspensions that are designed for reproducible zeta potential validation. A special formulation ensures that the negative charge is stronger than is the case with common polystyrene suspensions. The suspension has a negligible content of charged surfactant, resulting in the reduction of background noise. Applied Microspheres Zeta Potential Controls are supplied in single use, 3 ml or 10 ml luer lock syringes, packaged in boxes of 10 or 18 syringes. Shelf life is 18 months from date of packaging. They can be stored at room temperature.