System simplifies the standard ASTM method by eliminating complicated linear calibration steps for high-concentration compounds
Agilent Technologies has announced a new system for characterising high concentrations of aromatics in gasoline using the Agilent 5973 inert gas chromatography/mass spectrometry (GC/MS) system.
Using an extended linearity ion source kit, the new system simplifies the standard American Society of Testing and Materials (ASTM) D5769 method by eliminating the additional steps that are usually required to obtain linear calibration of high-concentration sample components.
Gasoline refiners adjust the levels of aromatic compounds in order to comply with environmental regulations and to improve product properties and performance.
The ASTM method analyses specific and total aromatic hydrocarbons in gasoline at concentrations from 0.1 to 42 weight percent.
Modern GC/MS systems are designed to provide sensitivity at trace levels with linear response over several orders of magnitude; when analysing compounds at high concentrations, however, the MS electron ionisation (EI) source can be saturated with sample, causing a nonlinear response over a narrow concentration range.
To overcome this problem, researchers have relied on a number of remedies, including custom mass spectrometer tuning, time-programmed interface splitters, very small injections, very large split ratios, nonlinear curve fitting, and a specialised inlet pressure programme.
These approaches significantly increase the time and effort required to perform ASTM D5769, which is already complex to set up and run. The new system consists of an Agilent 5973 inert GC/MS equipped with an optional extended linearity ion source kit.
The kit includes an EI source that is designed specifically for enhanced linearity, allowing scientists to quickly and easily obtain linear calibration curves for percent level components.
Agilent chemists determined that this system quickly and easily passes ASTM D5769 performance requirements for resolution, sensitivity and spectral integrity.
Further information is available by requesting the application note 'Improved Performance for the Analysis of Aromatics in Gasoline by ASTM Method D5769 Using the Agilent 5973 Inert Gas Chromatography/Mass Spectrometry System," Agilent publication 5989-0093EN.
This note is available without charge from any Agilent sales office or its website.
