In comparison with these reagents, Dragendorff’s reagent is more convenient alternative as it reacted at room temperature,besides it is had a lower cost. The color of the spot developed by Dragendorff,s reagent was orange with faint orange background, however the colors contrast was not
adequate for achieving good sensitivity. Therefore, the plate was sprayed with sodium nitrite solution (5%, w/v), which generates iodine from the previously applied Dragendorff,sreagent, when the plate was allowed to stand for some while,brown spots with light yellow background were developed.