Science with Passion
Application No.: VEV0080
Version 1 12/2017
Determination of mono- and polyaromatic hydrocarbons in diesel fuels with HPLC using RI detection
Lilit Avagyan¹, Stephanie Hutfless², Kate Monks¹; applications@knauer.net
1KNAUER Wissenschaftliche Geräte GmbH, Hegauer Weg 38, 14163 Berlin
²Haltermann Carless Deutschland GmbH, Hamburg, Germany
Summary
The content of aromatic hydrocarbons in diesel fuel has an influence on exhaust emission and its combustion characteristics. Here we present the determination of aromatic hydrocarbons under normal phase conditions with an isocratic AZURA® Analytical HPLC system and detection via refractive index detector AZURA RID 2.1L.
Introduction
It is well known that the best performance and maximum lifetime of an engine can be reached, when the amount of aromatic hydrocarbons in diesel and aviation turbine fuels is as low as possible. Since the aromatic hydrocarbon content can affect the cetane number of fuels and cause emissions due to incomplete burning, there are different regulations to protect the environment and public health. Below, we describe a method according to DIN EN 12916 [1] for the the determination of mono- and polyaromatic hydrocarbons, like 1,2-dimeth ylbenzene, fluorene, and phenanthrene in diesel fuel samples.
Results
The chromatographical results show that all three aromatic hydrocarbons in standard solutions were successfully separated under normal phase conditions and current instrumental settings. Fig 1 shows the overlay of chromatograms from three repetitions. The standard deviation value for retention time and peak area is 0.05 % – 0.06 % and 0.09 % – 0.22 %, respectively (Tab 2). The correlation factor for all compounds, obtained due analysis of three concentration levels (standard solutions A, C, and D) is > 0.9999. The corresponding overlay chromatograms are presented in Fig 2. In the chromatogram of the diesel fuel sample all three compounds could be identified (Fig 3). The highest amount of aromatic hydrocarbons was detected for 1,2-dimethylbenzene. The calculated value is 19.26 %. The values for all three hydrocarbons are presented in Tab 3.
Fig.1 Overlay chromatogram of three replicates of standard solution C
Tab.1 Amount of components in m% of standard solutions A, C, and D
Fig.2 Overlay chromatogram of two replicates each for standard solutions A (red), C (blue), and D (green)
Tab. 2 Reproducibility of standard solution C
Fig.3 Chromatogram of a diesel fuel sample
Tab.3 Calculated amount of identified components in diesel fuel
Materials and Methods
For the analysis of mono-, and polyaromatic hydrocarbons we used the following HPLC system setup: isocratic AZURA P6.1L pump with 10 mL pump head, AZURA AS 6.1L autosampler, AZURA RID 2.1L detector and AZURA CT 2.1L thermostat. The separation was performed on normal phase column ZORBAX®, NH2 250 x 4.6 mm. The used mobile phase was n-heptane. For calibration three concentration levels were used. The amounts of 1,2-dimethylbenzene, fluorene and phenanthrene in corresponding solutions A, C and D are presented in Tab 1. The samples from the respective diesel fuel batches were diluted to 10 % with n-Heptan and analyzed.
Conclusion
This application demonstrates, that the AZURA isocratic analytical HPLC system in combination with AZURA RID 2.1L detector suitable for determining of mono- and polyaromatic hydrocarbons in diesel fuel according to DIN EN 12916.
Additional Materials and Methods
Tab. A1 Method parameters
Tab.A2 System configuration
References
DIN EN 12916:2016 Petroleum products – Determination of aromatic hydrocarbon types in middle distillates – High performance liquid chromatography method with refractive index detection, German version
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Application details