Patent ID: 7595197

Claim:
A method of determining unknown concentrations of an inorganic ion of interest in a recovered sample comprising the steps of: providing a microfluidic device comprising a sample well having the recovered sample disposed therein, an indicator well having a fluorescent indicator disposed therein, a control well having a control disposed therein, the control including a known quantity of the inorganic ion of interest, a waste well, a detection region, and a light source directed at the detection region; wherein the sample well, the indicator well, and the waste well form a first fluidic circuit, the sample well fluidly coupled to the waste well via a first channel, and the indicator well fluidly connected to the first channel via a second channel; and wherein the indicator well, the control well, and the waste well form a second fluidic circuit, the indicator well fluidly coupled to the waste well via a third channel, and the control well fluidly coupled to the third channel via fourth, fifth, and sixth channels, each of the fourth, fifth, and sixth channels having a different flow resistance; mixing, in the third channel, the control sample and the fluorescent indicator, wherein flowing the control sample into the third channel via the fourth, fifth, and sixth channels provides a plurality of relative known ratios of the control sample in the indicator; obtaining a signal representative of the concentration of the inorganic ion of interest in each of the ratios, wherein the signal comprises an intensity of fluorescence; generating a model representative of the signal and the relative ratio of the control sample in the indicator; mixing, in the first channel, the recovered sample and the fluorescent indicator, and obtaining a signal representative of the concentration of the inorganic ion of interest therein, wherein the signal comprises an intensity of fluorescence; and comparing the signal representative of the inorganic ion of interest for the recovered sample within the model, thereby providing a determination of the concentration of the inorganic ion of interest present in the recovered sample.