Figure 9.

Intensity-and concentration-based ratio calculation. Intensity-based ratio calculation is accurate only when the calibration curve (I~C) is a linear and pass the origin (the dashed blue line). When the calibration curve is nonlinear (red curve), intensity-based ratio calculation underestimate the true concentration differences. Such an underestimation of concentration difference is universal for both two-color and one-color platforms. For one-color platform, the calibration functions f₁ and f₂ are the same, whereas for two-color platform, f₁ and f₂ reflect the differences of the two dyes as discussed in this study.