Editing ECL (section)

== Purification of p-iodophenol (PIP) and luminol<br>  ==

PIP is needed for enhancing the visible light reaction by acting as a co-factor for peroxide activity toward luminol, rather than participating directly in the luminescence itself. When phenolic enhancers are used in combination with HRP, the level of light is said to be increased about 100-fold. This is why the reaction has been dubbed `enhanced' chemiluminescence [2] or `ECL' (not to be confused with electrochemiluminescence, which has also been called by the same acronym ECL). 

The cheapest PIP be purchased from Aldrich or Fluka and then sublimed in-house at 85 degrees C under vacuum. This is extremely easy to do and results in beautiful white crystals of pure iodophenol as compared to the mucky yellow powder obtained from the chemical supply company. the commercially available apparatus for this is&nbsp; expensive, but that a cheaper homemade version can be made for little cost. 

To prepare luminol, suspend 3 g of the cheapest luminol in 90 ml of 1-butanol and to add 40 ml of 1M NaOH. After the luminol is dissolved by warming and agitating, 30 ml of methanol is added and the recipient cooled in ice before adding 40 ml of 1M HCl. This should then be left at -20 degrees C for 30 min for precipitation. The crystals are then filtered onto a Whatman No. 1 filter, rinsed with dichloromethane and dried under vacuum. To protect the crystals from light, the bottle or tube should be wrapped with a piece of aluminum foil and placed in a dessicator.<br>