High-Pressure Solubility of l-Methionine in Water

The solubility (mS) of l-methionine in water was measured at 298.2 K and pressures up to 200 MPa. The data were fitted to the equation ln(mS/mol·kg−1) = −4.62 × 10−6 (p/MPa)2 + 2.65 × 10−3 (p/MPa) − 0.970 with a standard deviation of σ(ln mS) = 0.002. The pressure coefficient of the logarithm of solubility (∂ln mS/∂p)T was thermodynamically estimated to be (2.62 ± 0.34) × 10−3 MPa−1 at 0.10 MPa using several parameters such as partial molar volume and activity coefficient of l-methionine in water and molar volume of solid l-methionine. The resulting value agrees well with the second term on the right-hand side of the fitted equation above, indicating the reliability of the high-pressure solubility measurements. The value of (∂ln mS/∂p)T also was compared with those of other amino acids.