A new length detection-micro fluidic device using an autocatalytic reaction

A new length detection-micro fluidic device was developed using a sodium sulfite/hydrogen peroxide autocatalytic reaction system as a model reaction, and sub-ppm levels of horse radish peroxidase were determined with this device. Sodium sulfite solution containing bromo thymol blue as an indicator and hydrogen peroxide solution were pumped into a T-shaped mixer with the help of a microliter syringe pump and then mixed. The blue solution had changed to yellow beyond the midpoint of the fine pathway (micro channel). Furthermore, when horse radish peroxidase (POx) was pumped, a part of the blue solution in the micro channel (blue band) was shortened. Therefore, it was possible to determine the POx concentration by via the length of the blue band. The relationship between the blue band length (y, mm) and the common logarithm of the POx concentration (x, M) gave a straight line in the concentration range of 0.05-1 ppm. The equation for the straight line was as follows: y = -3.78 log(x) + 16.4. The correlation coefficient was gamma = 0.995, the relative standard deviation was 5.7% (n = 10), and the detection limits of the POx concentration was 0.029 ppm.