DHA - Detailed Hydrocarbon Analysis

Importance of the Topic

Detailed hydrocarbon analysis (DHA) is a cornerstone technique in petroleum quality control and research. By resolving individual components in gasoline, naphtha, and middle distillates, DHA enables precise determination of composition, physical properties and performance-related parameters, supporting regulatory compliance, formulation optimization and fuel performance evaluation.

Objectives and Study Overview

This application note describes the implementation of ASTM, DIN, EN and IP standard methods for DHA using the G.A.S. Detailed Hydrocarbon Analyser coupled to a Thermo Trace 1300 GC. The goals are to achieve high-resolution separation of C1 to C16 components, automate identification and quantification, and calculate key group and physical property data for petroleum streams.

Methodology and Instrumentation

Samples are injected undiluted via a split-splitless inlet with a high split ratio to prevent column overload. A long, high-resolution capillary column provides maximal separation, while flame ionization detection (FID) ensures universal hydrocarbon response. Two common column configurations include Restek Rtx-1 (50 m×0.21 mm) for D5134 and Restek Rtx-DHA (100 m×0.25 mm) for D6729, with optional oxygenate-tuning columns available. Oven programming starts from 35 °C or lower using cryogenic cooling for light ends and olefin-rich samples. Analysis typically requires 140 min with helium carrier gas or 85 min using hydrogen. A backflush module can be added for front-end crude oil analysis of C1–C9 fractions.

Used Instrumentation

• Thermo Trace 1300 GC with low thermal mass oven for stable retention times
• iConnect SSL injector with optional backflush module
• FID detector
• Restek Rtx-1 and Rtx-DHA capillary columns (and tuning column)
• Triplus RSH or AS/AI-1310 autosampler

Main Results and Discussion

The integrated software calibrates using a C7–C40 alkane standard and computes retention time indices for peak identification against a database of over 500 components. Automated algorithms correct for peak distortion and predict true retention times for overloaded peaks. Results are reported in weight and volume percentages to 0.001% precision. Hydrocarbon group data (O-PIONA) and calculated physical properties—specific gravity, true boiling point distribution, motor octane number (MON), research octane number (RON) and vapor pressure—are automatically generated.

Benefits and Practical Applications

• Comprehensive compliance with ASTM D5134, D6729, D6730, D6733, IP PM DL and prEN 15199-4
• Fully automated workflow from injection to report export (PDF, CSV, XLS, RTF)
• High uptime via user-replaceable injector and detector modules
• Enhanced data reliability through database editor and quality algorithms
• Versatility for fuels, naphthas, middle distillates and crude fractions

Future Trends and Potential Applications

Advances in column technology, such as ultra-narrow bore and novel stationary phases, promise faster analysis times and improved resolution. Integration with high-resolution mass spectrometry could extend identification capabilities to non-hydrocarbon additives and contaminants. Automated database sharing and cloud-based analytics may further streamline method updates and interlaboratory comparisons.

Conclusion

The G.A.S. Detailed Hydrocarbon Analyser paired with the Thermo Trace 1300 GC delivers robust, fully automated DHA compliant with all major international standards. Its high-resolution separation, comprehensive software package and modular hardware design ensure precise component quantification, group classification and physical property determination for a wide range of petroleum samples.