Hi Annette,
Anatech make a refirm assay kit we use to monitor the 
concentration of our NBF, it can also be used to test formaldehyde.
Contact them on
ANATECH LTD
1020 Harts Lake Road
Battle Creek
Michigan, 49015
www.anatechltdusa.com
www.net-link.net/anatech
email:  email@anatechltdusa.com




Rosalba Zumbo
Technical Officer ( Scientific)
Institute of Forensic Medicine
Sydney, Australia
Fax 61 2 95664573