Which preservative can be used for the 2% aqueous solution of eosin now Thiomersal is no longer available?

Let me begin by alerting you to the detention of an eosin solution, which must always be prepared ex tempore unless certain conditions are respected. Sterilizes the solution preferably divided into small quantities (e.g. bottles of 100 ml) then the solution can be prepared in advance. Of course, the problem is still the use of my own! I recommend limiting this to 1 month and apply the same label as with eye drops. For the Microbi ë le Preservation of eosin solution mentions the literature: Nipagine and Nipasol, and Phenoxyethanol. This product is also not available at the wholesale! Also ethanol (20%) Used. In addition, it is mentioned that the activity of eosin increases in acidic middle (quite logical) and that in an acidic solution germ growth occurs more difficult.

following formulations may be recommended:

1. alcohol-based

   eosin 2 G
   fresh boiled water 38 g
   antiseptic solution 20 g
   Citric acid solution (0.2%) 40 g

   pH = 5.1

   The alcohol-free solution is better assumed as it does not squat in contact with hurt skin. But the drying effect (important aspect of the Eosin solution) is lower than that of alcoholic solutions.

2. without alcohol

   eosin 2 G
   fresh boiled water 48 g
   Citric acid solution (0.05%) 50 g

   pH = 5.35

   This should certainly be taken into account with the observations formulated above. In any case, the use of freshly boiled water and pre-sterilized (in a boiling pressure Pan bv) vials is a minimum!