Bioactive paper platform for detection of hydrogen peroxide in milk

This paper describes the development and application of a paper-based analytical device (μPAD) for the determination of hydrogen peroxide, an important adulterant in milk. The method employs the reaction between hydrogen peroxide and guaiacol, catalyzed by peroxidase, producing a red product, which is then quantified by digital imaging. Experimental design methodology was used to optimize the experimental conditions. The linear concentration range was from 12.5 × 10^-4 to 150 × 10^-4 mol L^-1, resulting in the regression equation A_B = 0.02466 (±0.00192) + 17.053 (±0.750) C, with an excellent correlation coefficient (r = 0.986). The relative standard deviations obtained were 1.1 and 1.3% (intra-day), and 4.8 and 2.9% (inter-day), for 25.0 × 10^-4 and 100 × 10^-4 mol L^-1 of hydrogen peroxide, respectively. The limits of detection and quantification were 3.54 × 10^-4 and 11.8 × 10^-4 mol L^-1, respectively, with standard deviation of the blank of 0.002012. The proposed method was successfully applied for the determination of peroxide in milk samples, with recoveries between 92.2 and 109%. The proposed device constitutes a valuable analytical tool for the identification of hydrogen peroxide adulteration and offers advantages including low cost, simplicity, portability, and no (or minimal) requirement for sample pretreatment.