Gas chromatograph DHA

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Overview
The purpose of detailed hydrocarbon analysis (DHA) is to determine the bulk hydrocarbon group-type composition (PONA: Paraffins, Olefins, Naphthenes and Aromatics) of gasoline and other spark-ignition engine fuels containing oxygenates (methanol, ethanol, MTBE, ETBE, TAME) according to ASTM-D6730. PONA identification is performed by matching retention indices with n-alkane standards. Chromatograms contain a large number of peaks; accurate and reproducible retention indices are essential to avoid erroneous PONA ratios. The Nexis GC-2030 with Advanced Flow Controller enables precise flow control and reproducible retention indices. Shimadzu offers DHA services and methods conforming to ASTM-D5134, ASTM-D6729, ASTM-D6730 and ASTM-D6733.

Analytical Conditions
Equipment: PONA System (Nexis GC-2030AF)
Column: Rtx-PONA, 100 m x 0.25 mm x 0.5 μm
Pre-column: Pre-PONA, 2 m x 0.25 mm x 1 μm
Column temperature program: 5 °C (hold 10 min) → 5 °C/min → 48 °C (hold 49 min) → 1.2 °C/min → 200 °C (5 min)
Carrier gas: He; split 1:150 (initial 5 min) then 1:20 for remainder
Sample size: 0.2 μL
Injector temperature: 250 °C
Detector temperature: 250 °C
Cryogenic option: CRG-2030 with liquid CO2

Example of a DHA analysis chromatogram (summary data)
Group Type | Total Mass% | Total Vol.% | Total Mol%
Paraffins | 15.868 | 17.1143 | 15.9838
Iso-Paraffins | 19.495 | 20.8586 | 19.1926
Olefins | 17.3556 | 18.5952 | 19.8748
Naphthenes | 20.6483 | 20.0522 | 21.3048
Aromatics | 23.5425 | 20.3256 | 21.8861
Total C14+ | 3.0907 | 3.054 | 1.7579
Total Unknowns | 0 | 0 | 0
Total Oxygenates | 0 | 0 | 0
Sample Total | 100 | 100 | 100
Multi-substituted Aromatics: 13.7740 (mass %), 11.8683 (vol. %)
Average Molecular Weight: 112.8396
Reid Vapor Pressure @ 100°F: 1.9378
Calculated Octane Number: 77.0250

Boiling Point Summary (by mass and vol.)
Property | IBP | T10 | T50 | T90 | FBP
BP by mass (°F) | 82.11 | 153.14 | 227.16 | 402.10 | 488.66
BP by vol. (°F) | 82.11 | 146.25 | 274.10 | 401.72 | 488.66
Percent Carbon: 86.7143 | Percent Hydrogen: 13.2857 | Bromine Number (Calc): 22.8036

Example of summary by group type & carbon number (mass %)
Carbon | Paraffins | I-Paraffins | Olefins | Naphthenes | Aromatics | Unknowns | Total
C1 | 0 | 0 | 0 | 0 | 0 | 0 | 0
C2 | 0 | 0 | 0 | 0 | 0 | 0 | 0
C3 | 0 | 0 | 0 | 0 | 0 | 0 | 0
C4 | 0 | 0 | 0 | 0 | 0 | 0 | 0
C5 | 2.61412 | 0.39222 | 2.12534 | 1.02294 | 0 | 0 | 6.15463
C6 | 1.75622 | 1.74186 | 3.4275 | 1.83233 | 1.5174 | 0 | 10.27531
C7 | 1.78205 | 3.41605 | 4.85244 | 3.76943 | 1.02589 | 0 | 14.84587
C8 | 1.68547 | 4.74174 | 2.49244 | 6.10152 | 3.72353 | 0 | 18.74469
C9 | 1.74756 | 5.41724 | 3.0002 | 5.20934 | 5.63764 | 0 | 21.01198
C10 | 1.60532 | 3.77676 | 1.45765 | 1.93379 | 6.87431 | 0 | 15.64782
C11 | 1.56754 | 0.0091 | 0 | 0.01491 | 1.45758 | 0 | 3.04912
C12 | 1.56411 | 0 | 0 | 0.76403 | 3.3061 | 0 | 5.63424
C13 | 1.54563 | 0 | 0 | 0 | 0 | 0 | 1.54563
Total C14+ 3.09070, Oxygenates 0.00000, Total Unknowns 0.00000, Grand Total 100.00000

Available software / downloads
Software for PONA/DHA analysis: PONAsolution for LabSolutions (brochure and documentation available).

Technical characteristics / specifications

• Application: Detailed Hydrocarbon Analysis (DHA) / PONA composition according to ASTM standards (ASTM-D5134, D6729, D6730, D6733)
• Recommended system: PONA System (Nexis GC-2030AF)
• Column: Rtx-PONA, 100 m x 0.25 mm x 0.5 μm
• Pre-column: Pre-PONA, 2 m x 0.25 mm x 1 μm
• Column temperature program: 5 °C (hold 10 min) → 5 °C/min → 48 °C (hold 49 min) → 1.2 °C/min → 200 °C (5 min)
• Carrier gas: Helium; split ratios: 1:150 (initial 5 min) then 1:20
• Sample volume: 0.2 μL
• Injector temperature: 250 °C
• Detector temperature: 250 °C
• Cryogenic option: CRG-2030 with liquid CO2
• Output: Group-type summary (mass%, vol%, mol%), carbon-number distribution, boiling point and derived properties (Average MW, RVP, Calculated Octane)
• Software: PONAsolution for LabSolutions (dedicated PONA/DHA analysis software)