This paper presents a novel pH measurement technique for microfluidic devices; “2-Color Laser-induced Fluorescence”. In this technique, an undesirable influence of excitation light distribution can be eliminated by dividing one fluorescence image with the other one taken at the same time. This can simplify measurement procedure in terms of omitting fluorescence intensity normalization at a lot of image locations, and measure a scalar distribution more accurately than 1-color LIF. In this study, the proposed method was applied to neutralization chemical reaction in T-type microchannel. Using Fluorescein and Rhodamine B, the divided value of fluorescence intensities was calibrated with 7 different pH solutions. Spatial intensity error can be reduced to about 80 to 90% as compared with 1-color LIF image. As a result, pH distribution of neutralization reaction between acetic acid and ammonia hydroxide at T-junction was visualized quantitatively at some flow rate conditions.
