ASTM D6733
ASTM D6733: Analysis of Hydrocarbon Components in Spark Ignition Engine Fuels by High Resolution Gas Chromatography
The ASTM D6733 Standard is a precise methodology for the analysis of individual hydrocarbon components in spark-ignition engine fuels, using a 50-metre capillary high-resolution gas chromatography. Initially adopted in 2001 and most recently revised in 2016, this standard offers a detailed framework for identifying hydrocarbons with boiling points up to 225°C in gasoline and other light liquid hydrocarbon mixtures common in petroleum refining, such as blending stocks. Specifically, it targets components within a concentration range of 0.10% to 15% by mass, although its applicability may extend beyond these limits with proper verification by users.
A significant aspect of ASTM D6733 is its utility in analyzing fuels blended with oxygenated compounds, which necessitates separate determination of the oxygenate content through specific ASTM methods. The method addresses the challenge of co-eluting compounds like benzene and toluene with others, necessitating their independent quantification using alternative ASTM standards to ensure accuracy. It's important to note that while the method aims for comprehensive coverage of hydrocarbon species, the potential for co-elution means some compounds may not be distinctly quantified, potentially affecting the accuracy of bulk hydrocarbon group-type composition (PONA) analyses.
This standard encompasses detailed procedures from the preparation and injection of samples into the gas chromatograph to the interpretation of chromatographic data. The equipment specified includes a gas chromatograph equipped with a flame ionization detector and a 50 m x 0.2 mm capillary column coated with a dimethylpolysiloxane stationary phase. The method outlines two sets of operating conditions for the chromatograph, emphasizing the importance of helium as the carrier gas and detailing the injector and detector temperatures among other critical parameters.
Quality control is a pivotal aspect, with detailed provisions for system performance evaluation, including criteria for column efficiency, resolution, and polarity, as well as the linearity of split injection. Reagents and materials are specified with purity requirements to ensure reliability and accuracy of the analysis.
The methodological rigor extends to sampling, with guidelines ensuring representative sample collection and preservation. Data acquisition systems are outlined with specific capabilities for peak identification and quantification, emphasizing the role of software in automating these processes.
For laboratories and analysts working with spark-ignition engine fuels, ASTM D6733 provides a comprehensive protocol for detailed speciation of hydrocarbon components. This can play a critical role in quality control, product specification, and regulatory compliance, offering insights into the composition of fuels and their blending components. The standard also highlights safety considerations and emphasizes the need for adherence to health and regulatory practices.