The dedicated gas chromatograph for aromatic hydrocarbon analysis in gasoline is suitable for determining the content of benzene, toluene, ethylbenzene, xylene, C9 and above heavy aromatic hydrocarbons, and total aromatic hydrocarbons in finished automotive gasoline. The separation of aromatic hydrocarbons in finished gasoline is not affected by non aromatic interference. Non aromatic hydrocarbons with boiling points greater than n-dodecane can interfere with the determination of heavy aromatic hydrocarbons above C9. For C8 aromatic hydrocarbons, both para xylene and meta xylene flow out simultaneously, while ethylbenzene and ortho xylene are detected as single peaks. C9 and above heavy aromatic hydrocarbons are detected as a group of peaks.
The concentration range of aromatic hydrocarbons determined by the analysis system is: benzene, 0.1%~5% (volume fraction); Toluene, 1%~15% (volume fraction); C8 mono aromatic component, 0.5%~10% (volume fraction); C9 and above heavy aromatic hydrocarbons, 5%~30% (volume fraction); Total aromatic hydrocarbons, 10%~80% (volume fraction).
The common alcohol and ether compounds in gasoline do not interfere with the determination of aromatic hydrocarbons.
The instrument system fully complies with ASTM D5580, SH/T 0693-2000 "Determination of Aromatic Hydrocarbon Content in Gasoline (Gas Chromatography Method)"; It is essential to analyze the aromatic hydrocarbon content in finished gasoline. Suitable for various types of finished gasoline, with a wide range of applications. The alcohol ether compounds added to gasoline do not interfere with the determination, and the instrument can also be extended to include the determination of oxygen-containing compounds.
System flowchart:

Analysis chromatogram of aromatic hydrocarbon content in gasoline:

Figure 2 Analysis of Aromatic Hydrocarbons in Gasoline (First Analysis, Using Micro filled Pre column)
1-Benzene; 2-Toluene; 3-2-hexanone; 4- Backblowing peak (C8 and above aromatic hydrocarbons and C9 and above non aromatic hydrocarbons)

Figure 3 Analysis of Aromatic Hydrocarbons in Gasoline (Second Analysis, Using Micro filled Pre column)
1-2-hexanone; 2-Ethylbenzene; 3- p-xylene/m-xylene; 4-o-xylene; Aromatic hydrocarbons above 5-C9

Figure 4 Analysis of Aromatic Hydrocarbons in Gasoline (First Analysis, Using Capillary Pre column)
1-Benzene; 2-4-methyl-2-pentanone; 3- Toluene; 4- Backblowing peak (C8 and above aromatic hydrocarbons and C9 and above non aromatic hydrocarbons)

Figure 5 Analysis of Aromatic Hydrocarbons in Gasoline (Second Analysis, Using Capillary Pre column)
1-4-methyl-2-pentanone; 2-Ethylbenzene; 3- p-xylene/m-xylene; 4-o-xylene; Aromatic hydrocarbons above 5-C9


working principle
As shown in the above figure, the system is a dual column gas chromatography system equipped with a ten way switching valve and a hydrogen flame ionization detector. The complete analysis process requires two injections to achieve. During the first injection, the sample containing the internal standard 2-hexanone was injected into a pre cut column containing a polar stationary phase of 1,2,3-tris (2-cyanoethoxy) propane. Non aromatic hydrocarbons smaller than C9 flow out of the pre cut column and are vented through the vent. This separation process can be monitored by a hydrogen flame detector or a thermal conductivity detector. Immediately place the pre cut column in a backflush state before the benzene flows out, and introduce the retained components into an analysis column containing non-polar stationary phase methyl silicone. Benzene, toluene, and internal standard flow out of the chromatographic column in boiling point order and are detected using a hydrogen flame ionization detector. After the internal standard substance flows out, immediately blow back the analysis column and blow back the remaining components (C8 and above heavy aromatic hydrocarbons and C10 and above non aromatic hydrocarbons) out of the chromatography column into the hydrogen flame ionization detector.
During the second injection analysis, the blowback time of the pre column is adjusted to be less than C12 for non aromatic hydrocarbons, benzene, and toluene before ethylbenzene flows out. The retained internal standard and C8 aromatic components are introduced into the analysis column and flow out in boiling point order for detection using a hydrogen flame ionization detector. When ortho xylene flows out, immediately blow back the analysis column and blow back the C9 or higher aromatic hydrocarbons from the chromatography column into the hydrogen flame ionization detector for detection.
Through the first analysis, the content of benzene and toluene can be obtained. Through the second analysis, the content of ethylbenzene, para/meta xylene, ortho xylene, and C9 or higher heavy aromatic hydrocarbons can be obtained. The total aromatic hydrocarbon content in the sample can be determined by two injections.

Instrument system configuration
1. Gas chromatograph (including split/non split injection ports, dual FID detection and monitoring, with automatic blowback and reset ten way switching valve)
2. Chromatographic column:
Pre cut column: 560mm long, 1.6mm outer diameter and 0.38mm inner diameter, micro filled column or 20m long, 0.35mm inner diameter capillary column.
Analysis column: a 30m long, 0.35mm or 0.53mm inner diameter cross-linked elastic quartz capillary column coated with 5.0Um or 2.6Um film thickness.
3. Chromatography workstation
4. Chromatographic gas source (high-purity nitrogen, high-purity hydrogen, pure dry air)
5. Standard samples
Mixing and cutting standard samples of iso octane solutions of benzene, ethylbenzene, o-xylene, and 2-hexanone (or 4-methyl-2-pentanone)
Qualitative standard sample of the sample
Calibration standard sample
Internal standard 2-hexanone standard sample
2,2,4-trimethylpentane (isooctane) solution of n-dodecane (for calibration)

2、 Special gas chromatograph for analysis of oxygen-containing compounds in gasoline
Scope of application:
The dedicated gas chromatograph for analyzing oxygen-containing compounds in gasoline is suitable for determining the content of alcohols and ethers in gasoline. The components measured are: methyl tert butyl ether (MTBE), ethyl tert butyl ether (ETBE), tert amyl methyl ether (TAME), diisopropyl ether (DIPE), methanol, ethanol, isopropanol, n-propanol, isobutanol, tert butanol, sec butanol, n-butanol, and tert pentanol (tert pentanol). The determination range of various ethers ranges from 0.1% to 20%; The determination range of various alcohols is from 0.1% to 12.0%.
This method is not applicable to alcohol based fuels such as M-85, E-85, MTBE products, ethanol products, and modified alcohols.
The instrument analysis system fully complies with ASTM D4815 or SH/T0663.




System flowchart:

working principle
Refer to Figure 5-4, introduce the sample with an appropriate internal standard [such as 1,2-dimethoxyethane (DME)] into the GC7860 gas chromatography analysis system equipped with two columns and a ten way switching valve. The sample first flows into the pre cut column, where it is gently rinsed and emptied. When methylcyclopentane flows out, switch the valve to the blowback position to allow the oxide to enter the analysis column. After benzene and tert amyl methyl ether (TAME) flow out of the analysis column, the ten way valve is switched back to the starting position to blow back the heavy hydrocarbon components in the analysis column to the detector. Record detector response values proportional to component concentration; Measure peak area; And by referring to the internal standard, the concentration of each component can be calculated.

Analysis chromatogram of alcohol and ether whole component standard samples
1 methanol 2 ethanol 3 isopropanol 4 tert butanol 5 n-propanol 6 methyl tert butyl ether 7 sec butanol 8 diisopropyl ether
9 isobutanol 10 tert amyl alcohol 11 ethylene glycol dimethyl ether 12 n-butanol 13 tert amyl methyl ether 14 heavy hydrocarbons

Instrument system configuration
1. Gas chromatograph (including split/non split injection ports, dual FID detection and monitoring, with automatic blowback and reset ten way switching valve)
2. Chromatographic column:
Pre column micro filled column: 0.56m long, 1/16in (lin=2.54cm) outer diameter.
Analysis column: 30m long, 0.53mm inner diameter, 5.0um liquid desert thickness.
3. Chromatography workstation
4. Chromatographic gas source (high-purity nitrogen, high-purity hydrogen, pure dry air)
5. Standard samples
Qualitative standard samples of alcohols and ethers
Alcohol and ether calibration standards
Internal standard 1,2-dimethoxyethane (DME)
System analysis cutting standard sample

3、 Special gas chromatograph for analysis of benzene and toluene in refined automotive and aviation gasoline

Scope of application:
The specialized gas chromatograph for analyzing benzene and toluene in refined automotive and aviation gasoline is suitable for determining the content of benzene and toluene in automotive and aviation gasoline. The range of benzene content determination is 0.1%~5% (volume fraction), and the toluene content is 2%~20% (volume fraction).
The ether compounds such as methyl tert butyl ether added to finished gasoline do not interfere with the determination of benzene and toluene. When using 1,2,3-tris (2-cyanoethoxy) propane (TCEP) packed column as the analytical column, it is not suitable for gasoline containing ethanol, and methanol may also cause interference. When using a modified polyethylene glycol (FFAP) capillary analysis column, the interference of methanol and ethanol is not significant.
This instrument fully complies with the ASTM D3606 method standard, with a simple system, easy operation, low investment cost, and easy maintenance; However, it is not suitable for determining the total aromatic hydrocarbon content in gasoline, nor is it suitable for determining the benzene content in ethanol gasoline.


Standard sample chart:

working principle
The dedicated gas chromatography analysis system for benzene and toluene in refined automotive and aviation gasoline consists of a six way valve, a pre column, and an analysis column. Pre column is a chromatographic column filled with a non-polar stationary phase (methyl silicone), which utilizes its characteristic of separating sample components in boiling point order to achieve pre separation of benzene and toluene from heavy hydrocarbons; The analytical column is a chromatographic column filled with a strongly polar stationary phase of 1,2,3-tris (2-cyanoethoxy) propane (TCEP) or modified polyethylene glycol (FFAP), mainly used for separating aromatic hydrocarbons and non aromatic compounds smaller than octane. The method uses thermal conductivity detector or hydrogen flame ionization detector for measurement and internal standard method for quantification. During analysis, butanone (MEK) is first added to the sample as an internal standard, and then introduced into the pre column. After the octane in the sample flows out of the pre column and enters the analysis column, the six way valve is placed in the blowback state. On the analysis column, the octane and light components are completely separated and detected by the detector. The peak area is measured, and the concentration of each component is calculated based on the internal standard.

Instrument system configuration
1. Gas chromatograph (FID detection, automatic blowback switching of ten way valve or six way valve)
2. Chromatographic column:
Pre cut column: Column length 1.0m, outer diameter 3.2mm, inner diameter 2.2mm, 10% methyl silicone (mass fraction)/60-80 mesh white silane carrier
Analysis column: column length 4.6m, outer diameter 3.0mm, inner diameter 2.0mm, TCEP， 15% or 20% (mass fraction)/Chromosorb P 80-100 mesh [or elastic quartz capillary FFAP 50m × 0.25mm]
3 Chromatography Workstation
4. Chromatographic gas source (high-purity nitrogen, high-purity hydrogen, pure dry air)
5. Standard samples
System cutting standard sample
Qualitative standard samples of benzene and toluene
Calibration standards for benzene and toluene
Internal standard substance butanone (MEK)


Example of analysis of benzene and toluene in gasoline:

Analysis standard spectrum of benzene and toluene in gasoline

Sample spectra for analysis of benzene and toluene in gasoline