Detection of Trace Elements in Urea by HR ICP-OES Application Note · PlasmaQuant 9100 Elite

Introduction

Urea is an organic compound that plays an important role in biological metabolism processes. Besides its physiological properties, synthetically synthesized urea has become a very meaningful compound in the clinical, pharmaceutical, and chemical industries. It is a starting material for the synthesis of a large number of chemicals including hydrazine and melamine that are further used for the production of resins eventually used as building materials. In agriculture, urea is a preferred compound to be used as fertilizer because of its high nitrogen content.

Another application with constantly rising importance is its use as an active ingredient in exhaust gas treatment processes such as SNCR and SCR for environmental protection purposes. In these processes, ammonia or urea is injected to the exhaust gases of power plants (incineration plants, gas turbines, etc.), utility vehicles, and automobiles to reduce the emission of NOX gases to the environment by reaction to harmless products such as water and nitrogen.

Due to its manifold application areas (chemistry, food and agriculture, environment, etc.), the quality of urea and its products is highly regulated. For instance, the quality of urea as NOX reduction agent AUS 32 in diesel engines is regulated by ISO 22241. Here, maximum limits for calcium, iron, copper, zinc, chromium, nickel, aluminum, magnesium, sodium, potassium, and phosphorus (as phosphate) are in the range of 0.2 to 0.5 mg/kg. Nevertheless, the demands for other application areas might be more stringent, and QC laboratories aim towards lower matrix-specific limits of detection for specification analysis

The proposed method for trace element detection is by ICP optical emission spectroscopy. For the product control of urea by ICP-OES, high precision and the lowest detection limits are desirable, yet the detectability of many trace elements is affected by signal suppression and drifting (matrix load) as well as by spectral interferences. The latter often require less sensitive alternative lines to be used. When using the High-Resolution Array ICP-OES, many of these analytical shortcomings can be avoided.

Here, the exceptionally high spectral resolution and sensitivity of the PlasmaQuant 9100 Elite by Analytik Jena offers a new analytical potential! It allows for an interference-free analysis of trace elements in a complicated matrix such as urea. Furthermore, the high plasma robustness of the high-frequency generator and the sample introduction system with its centerpiece, the V-Shuttle torch, allow for the analysis of high matrix samples with high accuracy and precision. Within this study, the PlasmaQuant 9100 Elite was evaluated regarding the matrix specific detection limits for twenty commonly tested trace elements. Furthermore, the analysis of a QC control standard was included for method validation and long-term stability testing.