This paper reports the pH values of five NaCl-free buffer solutions and 11 buffer compositions containing NaCl at I = 0.16 mol . kg (1). Conventional pa(H) values are reported for 16 buffer solutions with and without NaCl salt. The operational pH values have been calculated for five buffer solutions and are recommended as pH standards at T = ( 298.15 and 310.15) K after correcting the liquid junction potentials. For buffer solutions with the composition m(1) = 0.04 mol . kg(1), m(2) = 0.08 mol . kg(1), m(3) = 0.08 mol . kg(1) at I = 0.16 mol . kg(1), the pH at 310.15 K is 7.269, which is close to 7.407, the pH of blood serum. It is recommended as a pH standard for biological specimens. (C) 2011 Elsevier Ltd. All rights reserved.