抄録
The protein error in a urine pH measurement by a test strip using mixed indicators of methyl red (MR) and bromothymol blue (BTB) was investigated mainly by a calculation based on the chemical equilibrium. In the pH region that is a part of the visual-transition interval for MR, a positive error occurs, and in the pH region including the visual-transition interval for BTB, a negative error occurs. With increasing pH, the positive error decreases and the negative error increases. The measurement error increases as the protein concentration increases and the concentration of a pH indicator decreases. These calculated results showed the same tendency as a laboratory finding with a test strip.
