||"In Table 1 [BNID 110745], the values refer to the concentrations of the “free” ions, which may differ from the total concentration of the ion in plasma or cytoplasm. The total Ca2+ concentration in plasma, for example, is ~2.5mM, but ~50% is bound to proteins, phosphate, and organic anions. The free [Ca2+] is only ~1.3mM. Similarly, the free [Mg2+] is ~50% of the total Mg2+ concentration. This binding/buffering is even more pronounced in the intracellular compartment. For H+, the buffer capacity ß is defined as (primary source) ß=?B/?pH, (eq.1) where B is the amount of strong base that is needed to produce a given change in pH. ß˜50mmole/(LXpH). The intracellular fluid is well buffered."