Next we demonstrated a 2-inlet spectofluidic device design to study reaction kinetics. After entering the device, fluid streams were led to a zigzag mixing channel with reduced width (100 m) before entering a reaction monitoring compartment atop the multi-ridge ATR crystal. The reaction monitoring chamber consisted of a series of switchback which were co-linear to the from each channel during reaction. Spectra from top to bottom corresponded to channel 1 to channel 7. (f) Calculated concentration of HPO4 2-and pH in channel 1 to channel 7 using the integration values of peak intensity at 988 cm -1 . The width of aperture is 0.4 mm.