Active fluoride concentration in the cavity varnish duraphat is:

Duraphat, the first fluoride varnish developed in Germany. It is a viscous yellowish material, containing 22,600 ppm fluoride as sodium fluoride in a neutral colophonium base (NaF varnish containing 2.26% fluoride in organic lacquer).  Duraphat has shown caries reduction between 30% and 40% in the permanent dentition and in between 7% and 44% in the primary dentition. Essentials of preventive and community dentistry Soben Peter 5th edition page no. 255