Raw and untreated beads are contaminated with broken beads, dust, microbes and other impurities all of which can significantly affect homogenization and downstream biological processes. With silica beads, impurities can attain such a high concentration as to inhibit many enzymes and reduce the amount of analytes liberated during homogenization. Quality control analysis of raw silica and zirconium beads has identified dust, hair, and insects as contaminants. Beads need to be cleaned prior to use and the accepted procedure is washing with dilute acid, which helps to reduce and eliminate fine particles and contaminants. Acid washing also removes potentially deleterious heavy metals adsorbed to the surface of the bead. Acid washed beads are oven dried and baked prior to bottling, at which time they are suitable for most applications.
Available in both silica (glass beads) and zirconium oxide in nine sizes. Glass beads are good for general grinding applications while zirconium beads have greater density and thus higher impact power. Acid washed glass beads have also been used successfully in filtration applications.
Recommend size applications for grinding:
100 µm - Bacteria, sonication additive
200 μm - Bacteria, small yeasts (e.g., Pichia)
400 μm - Yeasts (Saccharomyces)
800 μm - Molds, pollen
1.0 mm - Soft tissues, leaf tissue, insects
1.4 mm - Soft tissues, leaf tissue, insects
1.7 mm - Tissue, leaf tissue
3.0 mm - Resilient tissue, plant material