Analysis and Air Quality Section, Air Quality Research Division, Atmospheric Science and Technology Directorate, Science and Technology Branch, Environment Canada, Ottawa, Ontario, Canada K1A 0H3.
J Chromatogr A. 2012 Mar 16;1229:208-15. doi: 10.1016/j.chroma.2012.01.046. Epub 2012 Jan 24.
The use of urea based selective catalytic reduction (SCR) technology for the reduction of NOx from the exhaust of diesel-powered vehicles has the potential to emit at least six thermal decomposition by-products, ammonia, and unreacted urea from the tailpipe. These compounds may include: biuret, dicyandiamine, cyanuric acid, ammelide, ammeline and melamine. In the present study, a simple, sensitive and reliable hydrophilic interaction liquid chromatography (HILIC)-electrospray ionization (ESI)/mass spectrometry (MS) method without complex sample pre-treatment was developed for identification and determination of urea decomposition by-products in diesel exhaust. Gradient separation was performed on a SeQuant ZIC-HILIC column with a highly polar zwitterionic stationary phase, and using a mobile phase consisting of acetonitrile (eluent A) and 15 mM ammonium formate (pH 6; eluent B). Detection and quantification were performed using a quadrupole ESI/MS operated simultaneously in negative and positive mode. With 10 μL injection volume, LODs for all target analytes were in the range of 0.2-3 μg/L. The method showed a good inter-day precision of retention time (RSD<0.5%) and peak area (RSD<3%). Satisfactory extraction recoveries from spiked blanks ranged between 96 and 98%. Analyses of samples collected during transient chassis dynamometer tests of a bus engine equipped with a diesel particulate filter (DPF) and urea based SCR technology showed the presence of five target analytes with cyanuric acid and ammelide the most abundant compounds in the exhaust.
基于尿素的选择性催化还原 (SCR) 技术用于减少柴油动力车辆尾气中的氮氧化物，有可能从排气管中排放出至少六种热分解副产物、氨和未反应的尿素。这些化合物可能包括：缩二脲、双氰胺、三聚氰胺酸、三聚氰胺酰胺、三聚氰胺和三聚氰胺。在本研究中，开发了一种简单、灵敏和可靠的亲水相互作用液相色谱 (HILIC)-电喷雾电离 (ESI)/质谱 (MS) 方法，无需复杂的样品前处理，用于鉴定和测定柴油尾气中的尿素分解产物。在具有强极性两性离子固定相的 SeQuant ZIC-HILIC 柱上进行梯度分离，使用由乙腈（洗脱剂 A）和 15 mM 甲酸铵（pH 6；洗脱剂 B）组成的流动相。采用正负离子同时检测的四极杆 ESI/MS 进行检测和定量。采用 10 μL 进样量，所有目标分析物的检出限均在 0.2-3 μg/L 范围内。该方法显示出良好的日内精密度，保留时间（RSD<0.5%）和峰面积（RSD<3%）。从加标空白中提取的回收率令人满意，介于 96%至 98%之间。对装有柴油颗粒过滤器 (DPF) 和基于尿素的 SCR 技术的客车发动机在瞬态底盘测功机测试期间收集的样品进行分析，结果表明在尾气中存在五种目标分析物，其中三聚氰胺酸和三聚氰胺酰胺含量最丰富。
