High-Pressure Solubility of l -Methionine in Water

The solubility ( m S ) 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( m S /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 m S ) = 0.002. The pressure coefficient of the logarithm of solubility (∂ln m S /∂ 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 m S /∂ p ) T also was compared with those of other amino acids.