Notes on Protein Error Trend in pH Test Strips

Abstract

The measurement error due to protein in measuring the pH by a test strip was analyzed based on the chemical equilibrium of a protein error. The measurement error depends on the ratio of the molar absorptivities of the dissociated molecule of a pH indicator and the pH indicator-protein complex, the concentrations of a pH indicator and protein and pH; it becomes a positive error or a negative error. However, the pH at which no measurement error occurs also exists, and depends on the ratio of the molar absorptivities of the dissociated molecule of a pH indicator and the pH indicator-protein complex. This pH is higher than the pK_D value of a pH indicator in the case that this ratio is large, and is lower than it in case that this ratio is small. The measurement error increases as the protein concentration increases and the dye concentration decreases. In addition, as the pH rises, a positive error decreases and a negative error increases.