Diesel exhaust fluid (DEF) is an aqueous urea solution made with 32.5% urea and 67.5% deionized water. It is standardised as AUS 32 (aqueous urea solution) in ISO 22241 and often referred to as AdBlue in many markets.

AdBlue is necessary to clean up the diesel emissions known in the latest technology called SCR. A solution of urea in water is used to treat the harmful gases coming out from the exhaust to convert into nitrogen and water. AdBlue is a registered trademark owned by the German Automobile Association (VDA) , which ensures the standards are maintained.

ISO 22241-1 DEF, Adblue tests:

1. ISO 22241-2 Annex B/C Urea Content
2. ISO 12185 Density at 20C
3. ISO 22241-2 Annex C Refractive Index at 20C
4. ISO 22241-2 Annex D Alkalinity as NH3
5. ISO 22241-2 Annex E Biuret content
6. ISO 22241-2 Annex F Aldehydes content
7. ISO 22241-2 Annex G Insoluble Matter content
8. ISO 22241-2 Annex H Phosphate (PO4)
9. ISO 22241-2 Annex I Ca, Fe, Cu, Zn, Cr, Ni, Al, Mg, Na, K (ICP-OES)
10. ISO 22241-2 Annex J Identity (FTIR)