Protein effect on the antimony microelectrode in application to biological fluid

In order to examine the effect of protein on the Sb-microelectrode used for the pH measurement of biological fluids, bovine serum albumin (BSA) and plasma protein were used for test samples. It was found that, BSA, probably by binding to components in the electrode system, produced a marked deviation of both the electromotive force and slope constant of the microelectrode, resulting in an alkaline shift of pH of 0.1-0.7. But the shift of the pH reading could be empirically predicated within an error of +/- 0.03 from the cubic function of protein concentration. Use of Tris standard solution as the calibration buffer, together with corrections for the effects of temperature, ionic strength, Po2, etc. on the Sb-microelectrode, would reduce the alkaline shift to approximately less than 0.08 and 0.04 pH units in the pH measurement of blood plasma and whole blood, respectively.