A fluorescence-based pH sensor with microfluidic mixing and fiber optic detection for wide range pH measurements

Highlights

• The fabricated pH meter on a microfluidic platform is simple and easy to manufacture and utilizes fluorescence intensity of a dye indicator.

• A single dye indicator (HPTS) is used as the fluorescence dye indicator.

• The fabricated device has a wide detecting range between pHs of 2.5 – 9.

Abstract

A fluorescence-based pH sensor based on a microfluidic chip is described. The indicator dye, 8-hydroxypyrene- 1,3,6-trisulfonic acid trisodium salt (HPTS) and the test solution are mixed in the microfluidic chip. Light fluorescing from this mixture is collected by a multi-mode optical fibre and its intensity is measured with a photodiode. The sensor is calibrated using a range of HPTS concentrations The highest sensitivity is achieved for a 500 mg L-1 solution of HPTS. Using this concentration of HPTS, the pH of test solutions, with pH ranging from 2.5 to 9.0, are measured. Results show a linear relationship between fluorescence intensity and pH within three pH ranges (i.e. 5.7 – 9.0; 4.2 – 5.7; 3.4 – 4.2) and a polynomial relationship within the pH range 2.5 – 3.3. Within the linear regions, the regression coefficients are greater than 0.99. Within the non-linear region the regression coefficient is 0.98.

Moradi V., Akbari M. & Wild P., in press. A fluorescence-based pH sensor with microfluidic mixing and fiber optic detection for wide range pH measurements. Sensors and Actuators A: Physical. Article (subscription required).

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