PBS (phosphate buffered saline) is a pH-adjusted blend of ultrapure-grade phosphate buffers and saline solutions which, when diluted to a 1X working concentration, contains 137 mM NaCl, 2.7 mM KCl, 8 mM Na₂HPO₄, and 2 mM KH₂PO₄. Each 10X PBS solution is ready to use upon dilution to the desired concentration. This molecular biology-grade PBS is certified RNase-free; it is rigorously tested for contaminating nonspecific endonuclease, exonuclease, and RNase activity.