Diesel Exhausted Fluid (DEF)


To reduce emissions from diesel engines, especially nitrogen oxides (NOx), selective catalytic reduction (SCR) and exhaust gas recirculation (EGR) technologies are used. SCR requires a high-quality diesel exhaust fluid (DEF), also known as AUS 32 (aqueous urea solution), to treat exhaust gases and remove harmful pollutants, especially nitrogen dioxide (NO2).

AUS 32 consists of a high purity 32.5% solution of urea in water and is stored in its own tank in the car. Its widespread introduction coincided with the current Euro 6 emissions standards, which are part of ever more stringent emissions targets that car manufacturers are now required to meet.

The “AdBlue” trade name, which is registered by the German car manufacturers association (Verband der Automobilindustrie, VDA), is the best-known AUS 32 diesel exhaust fluid (2). VDA issues licenses to any manufacturers of AUS 32 wishing to use the trade name AdBlue. However, to maintain the quality of AdBlue, all licensees must adhere to ISO 22241 standards. The ISO 22241 guidelines also ensure that AUS 32 products comply with the requirements specified by engine manufacturers or government regulations.

CCIC Singapore provides the following tests in accordance with ISO-22241-2 standards.

NoTest ItemUnitLimitMethod
1Urea Content%mass31.8-33.2ISO 22241-2 Annex B
2Refractive Index(nD20)1.3814-1.3843ISO 22241-2 Annex C
3Alkalinility as NH3%mass0.2 MaxISO 22241-2 Annex D
4Biuret%mass0.3 MaxISO 22241-2 Annex E
5Aldehydesmg/kg5 MaxISO 22241-2 Annex F
6Insoluble mattermg/kg20 MaxISO 22241-2 Annex G
7Phosphate(PO4)mg/kg0.5 MaxISO 22241-2 Annex I
8Aluminiummg/kg0.5 MaxISO 22241-2 Annex I
9Calciummg/kg0.5 MaxISO 22241-2 Annex I
10Chromiummg/kg0.5 MaxISO 22241-2 Annex I
11Coppermg/kg0.5 MaxISO 22241-2 Annex I
12Ironmg/kg0.5 MaxISO 22241-2 Annex I
13Potassiummg/kg0.5 MaxISO 22241-2 Annex I
14Magnesiummg/kg0.5 MaxISO 22241-2 Annex I
15Sodiummg/kg0.5 MaxISO 22241-2 Annex I
16Nickelmg/kg0.5 MaxISO 22241-2 Annex I
17Zincmg/kg0.5 MaxISO 22241-2 Annex I
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