Microfluidic colorimetric system for nitrite detection in foods

A microfluidic colorimetric system comprising of a colorimetric paper-chip device and a microanalysis cassette is presented for detecting the nitrite concentration in foods. In the proposed system, 1 μl of nitrite sample is dropped into the reaction region of the colorimetric paper-chip device, where its reacts with embedded Griess reagent to produce a pink complex. A color image of the reaction complex is caught using an embedded camera and transmitted to a cell phone within the microanalysis cassette via a WiFi connection. Finally, the images were analyzed by self-written RGB (Red, Green, and Blue) software to evaluate the nitrite concentration. The results acquired for 11 known nitrite solutions ranging from 1 to 100 ppm show that the measured R + G + B intensity is related to the nitrite concentration, and the determination coefficient (R²) are 0.9908 and 0.9948 in the two concentration ranges of 1–50 ppm and 50–100 ppm, respectively. The practical feasibility of the current microfluidic system is indicated by analysis the nitrite concentrations of 24 actual samples. Therefore, the difference between the concentration analysis obtained with the current system differ from those obtained using a conventional TFDA (Taiwan Food and Drug Administration) standard method by no more than 7.3%. Furthermore, the detection limit is just 1 ppm.