The pressure-induced pH shift depends on pressure, V 0 value,
and the number of charges of the anion (El’Yanov and Hamann´
1975). Reestablishment of the initial pH value occurs upon pressure
release. The pressure-induced pH reduction predicted by Eq. (1) for
citric acid buffer pressurized to 650 MPa is 0.7 and 1.25 pH units
from an initial pH value of 4.75 and 6.5, respectively (Figure 2). At
550 MPa, the corresponding pH shift values are 0.6 and 1.1, respectively. It should be noted that there is no data to estimate the effect
of temperature on this pH s