By David Taiwo Ajayi
Year 2023
Abstract
Herein, a microfluidic paper-based analytical device (μPAD) was developed for calcium determination in milk samples, and a microfluidic thread-based analytical device (μTAD) for nitrite and nitrate determination in processed meat samples.
The μPAD utilized a complexometric reaction between Ca2+ and ethylene diamine tetra-acetic acid (EDTA) with murexide as an indicator and a smartphone as a detector. By using a nanosilica-coated cotton thread, the μTAD detection principle was based on the modified Griess reaction, wherein sulfanilamide and N-(1-naphthyl) ethylenediamine were chromogenic reagents, and a distance-based detection technique was utilized. Polylactic acid was applied to one end of the nanosilica-coated thread to constrain the fluid flow along the thread in one direction.
The proposed μPAD exhibited a good linear detection range (1 – 10 mM), a low detection limit of 0.42 mM, and a short analysis time of 2 mins. The detection of calcium in milk samples using the proposed μPAD was consistent with the potentiometric method. When the proposed μTAD was tested, linear responses were observed in a range of 4 – 25 mg L-1 for nitrite and a range of 8 – 50 mg L-1 for nitrate. The detection limits for nitrite and nitrate were 1.47 and 3.06 mg L-1, respectively. The detection time was 5 mins. for nitrite analysis, and 7 mins. for nitrate analysis. The performance of the proposed
μTAD for nitrite and nitrate determination in real food samples was comparable to that of the conventional UV-Vis spectrophotometric method. The proposed microfluidic-based devices had many advantages, including rapid detection, acceptable precision and accuracy, low cost, low sample volume, and suitability for on-site quantification of calcium, nitrate, and nitrite in real samples.