2.3. RGB capturing system and procedure
A custom-built color detection box (Fig. 1) was used to eliminate any effects from environmental light. The box (8.0 cm × 11.0 cm × 5.5 cm) was made of opaque black corrugated plastic board with an internal white background. A flat cap PCR micro-tube was hung at the top of the box as a reaction container. A 5 W cool daylight Philips light bulb was put at the top of the box as the upper light source, 2 cm from the micro-tube (this was found to be the optimal distance). The intensity of the color product inside the micro-tube was detected using the ColorAssist app (FTLapps, Inc.) for an iPhone 4.0 in the flash-off mode.