page_title: Quinaldine red
section_title: Properties
hierarchical_section_title: Quinaldine red / Properties
caption_attribution_description: English: Chemistry
context_page_description: Quinaldine red is a dark green–red or black solid that does not dissolve easily in water. In addition to being used as colored indicator, quinaldine red is also used as a fluorescence probe and an agent in bleaching.
context_section_description: Quinaldine red is an indicator that turns from colorless to red between a pH of 1.0–2.2. The image below shows what color quinaldine red would appear as in a given pH.
  It is a cationic molecule that undergoes oxidation at different levels of pH. The rate of oxidation of Quinaldine red is in the first order with respect to the concentration of the oxidizing agent. 
  Other factors that increases the rate of oxidation includes increasing pH and increased sodium carbonate concentration. The reaction rate eventually levels off due to the maximum formation of the product within the oxidation process.
  Quinaldine red also has the ability to fluoresce. Free quinaldine red does not fluoresce in solution when it is not bound to anything, making quinaldine red only visible by fluorescence when it is bound to something. Quinaldine red can exhibit fluorescence when it is bound to nucleic acids, which then emit radiation between 580-650 nm.
   Maximum fluorescence of QR is detected from 557 nm to 607 nm. QR and the nucleic acids react quickly under room temperature, and the resulting QR-nucleic acid complex is able to fluorescence. However, fluorescent activity decrease as time goes on. Maximum fluorescence between QR and DNA is found within the pH range of 3.2-3.6, with the optimum being a pH 3.5. The amount of fluorescence seen with the use of QR is linearly related to the concentrations of DNA or RNA.
caption: Color change of Quinaldine red in pH change
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