The scanometric method is simply defined as a branch of the colorimetric method that employed a flatbed scanner to obtain an analytical signal by color intensity measurement. Here, we use a paper-based sensor that is simply fabricated by immobilizing antioxidant reagent (e.g. DPPH) onto the circular patterns on the filter paper which acts as the sensing zone, as it can be seen in Video 1.
In general, the sample solution is transferred onto the sensing zone next to the blank sensing zone as depicted in Video 2.
As presented in Video 3, an ordinary document scanner or flatbed scanner is then used to capture the color change of the sensing zone as a result of the chemical reaction between the sample and immobilized DPPH.
In a practical sense, the scanned image can be cropped to simplify the color measurement and to reduce the size of the image file as well, as presented in Video 4.
The color intensity of the cropped image is then quantified with a color image program (i.e. ImageJ) to generate the average value of red (R), green (G), blue (B), or the combined red–green–blue (RGB) color respectively, as shown in Video 5. For analytical purposes, each color value of the sample addition is subtracted from that of the blank sensing zone.