Citifluor AF4, glycerol mountant solution
Citifluor AF4 is a mountant solution composed of glycerol and the antifadent n-propyl gallate. N-Propyl gallate is a well established antifadent and is particularly useful for stopping the photo bleaching of DAPI and Alexa dye, Cye (cyanine) dyes, Hoechst dye stained as well as FITC labelled materials. It is ideal for examining tissue sections and dead cells. An aqueous solution (75%AF4 to 25% water v/v) has a pH of ~5. Citifluor AF4 may be mixed with buffer solutions in order to attain the correct pH for the fluorochrome being used but the resulting solutions may start to show discolouration within a few hours due to oxidation of the phenol. The solution should be pipetted onto the specimen (which has been copiously washed with the appropriate buffer) and then a cover slip applied. If the slides are stored in a refrigerator, the viscosity of the mountant solution increases thereby helping too keep the cover slip in place. There is no need to seal the cover slip with nail varnish.
The solutions are of medium viscosity and are water-white in appearance. They may be stored at room temperature and ideally between 50 and 150 and out of strong sunlight. The cap of the bottle should always be replaced after use as a matter of good practice and also to prevent the ingress of water (due to the glycerol being hygroscopic). Samples stored under these conditions for 6 months have shown no apparent deterioration. If the Citifluor AF4 solution is being used in an assay, a control experiment should always be carried out.