Overview
ISO 22241-2:2019 - "Diesel engines - NOx reduction agent AUS 32 - Part 2: Test methods" defines the analytical and sampling procedures needed to verify the chemical quality of AUS 32 (aqueous urea solution) as required by ISO 22241-1. The standard specifies how to take representative samples, how to measure key chemical characteristics, and how to interpret results including precision and dispute procedures. It includes normative test methods (Annexes B–I) and informative guidance (Annex J) for identity checks, plus precision data (Annex K).
Key technical topics and requirements
- Scope and purpose: Test methods required to determine AUS 32 quality and chemical characteristics (complements ISO 22241-1). Applicable urea concentration range noted for some methods (e.g., 30–35 % mass fraction for total nitrogen method).
- Sampling (Annex A):
- Use 1 000 ml wide-neck bottles made of HDPE, HDPP, PVDF or PFA.
- Flush sampling line, discard first fill, then immediately refill and seal.
- Transport/store at low temperatures (preferably 0 °C to 15 °C) and analyze within three weeks to account for ammonia changes.
- Minimum recommended sample: 1 litre; detailed labelling requirements provided.
- Analytical test methods (Annexes B–I):
- Annex B - Urea content by total nitrogen (combustion/thermal-conductivity detection).
- Annex C - Refractive index and refractive-index-based urea determination.
- Annex D - Alkalinity determination.
- Annex E - Biuret content determination.
- Annex F - Aldehyde content determination.
- Annex G - Insoluble matter by gravimetric method.
- Annex H - Phosphate content by photometric method.
- Annex I - Trace elements (Al, Ca, Cr, Cu, Fe, K, Mg, Na, Ni, P, Zn) by ICP‑OES.
- Annex J (informative) - Identity confirmation using FTIR spectrometry.
- Precision and dispute: Each method includes precision statements per ISO 4259; disputes resolved using ISO 4259 procedures.
- Safety note: Users must manage hazards associated with reagents and test equipment.
Practical applications and users
- Who uses it: AUS 32 manufacturers, chemical and fuel laboratories, automotive OEMs, fleet operators, quality auditors, regulatory bodies, and suppliers in the SCR (Selective Catalytic Reduction) supply chain.
- Why it’s used:
- Ensure AUS 32 conforms to ISO 22241-1 quality limits (protects NOx reduction systems).
- Provide reproducible sampling and test methods for contract verification and dispute resolution.
- Support quality control, incoming inspection, certification, and compliance testing.
Related standards
- ISO 22241-1 - Quality requirements for AUS 32
- ISO 3696 - Water for analytical laboratory use
- ISO 12185 - Density determination (oscillating U-tube)
- ISO 4259 - Precision and dispute resolution for test methods
Keywords: ISO 22241-2:2019, AUS 32 test methods, urea solution, NOx reduction agent, AUS32 sampling, ICP‑OES, FTIR, refractive index, biuret, phosphate, aldehyde, ISO 22241 series.
