Determination of Trace Elements in Aqueous Urea Solution Diesel Exhaust Fluid by ICP-OES

Poor ambient air quality in many towns and cities around the world is a major health concern. While different factors contribute to the problem, emissions from road transport are one of the biggest sources of pollutants. To reduce emissions from motor vehicles across India, the government will introduce and enforce new standards on 1 April 2020. The Bharat Stage VI (BS-VI) standards, which supersede the existing BS-IV norms, are in line with the Euro VI standards that have already been adopted in many European countries.

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. Unlike fuel, AUS 32 is not introduced into the engine but is injected into the flow of exhaust gases, where a chemical reaction converts NOx into harmless nitrogen and water.

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. 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. The maximum allowable concentrations for elemental impurities in AUS 32 per ISO-22241-1 quality requirements are given in Table 1. The ISO 22241-2 test method for the determination of trace element content of AUS 32 uses ICP-OES.

For efficient elemental analysis, the Agilent 5800 ICP-OES uses enabling technologies such as IntelliQuant to provide detailed information on samples, and get the right results the first time. IntelliQuant captures data from the entire wavelength range as each sample is measured, then uses the data to calculate the approximate concentration of up to 70 elements in the sample. The extra information provided by IntelliQuant ensures that high-quality results are produced first time, without the need to remeasure samples or standards.

The 5800 ICP-OES uses a series of sensors together with the smart early maintenance feedback (EMF) feature to identify problems before they happen, maximizing instrument uptime and maintaining analytical performance. EMF can also be used to prompt maintenance after a specific parameter has been met, such as the number of samples measured or the time that the plasma has been turned on.

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