A method for determination of pH using a T-sensor

A model-based method for the determination of constituent concentrations in flowing nano-liter volumes of liquid is presented. This method is applied to pH measurement. A T-sensor is used to bring sample fluid into contact with indicator fluid to produce low Reynolds number, co-flowing streams in a micro-channel. By diffusion, the sample stream ions are brought into contact with the indicator stream dye molecules to produce an optically detectable signal. An analytical model of the resulting dispersion process that takes into account the different physical properties of each stream and the effects of ideal buffering is used to determine the incoming sample stream pH.