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D5986-23 – Standard Test Method Technical Guide
The ASTM D5986-23 standard specifies a gas chromatography/Fourier transform infrared spectroscopy (GC/FTIR) method for determining oxygenates, benzene, toluene, C8–C12 aromatics, and total aromatics in finished motor gasoline. This method is crucial for regulatory compliance and fuel quality assessment.
📐 Scope and Concentration Ranges
This test method quantitatively determines various oxygenates including methyl-t-butylether (MTBE), ethanol (EtOH), and benzene, among others. The concentration ranges covered are: 0.1 % to 20 % by volume for ethers and alcohols; 0.1 % to 2 % for benzene; 1 % to 15 % for toluene; and 10 % to 40 % for total aromatics (C6–C12). The method is applicable only to finished gasoline and not to refinery process streams.
| 🟦 Compound Category | 📏 Concentration Range (% v/v) |
|---|---|
| Ethers (MTBE, DIPE, ETBE, TAME) | 0.1 – 20 |
| Alcohols (MeOH, EtOH, 2-PrOH, etc.) | 0.1 – 20 |
| Benzene | 0.1 – 2 |
| Toluene | 1 – 15 |
| Total Aromatics (C6–C12) | 10 – 40 |
⚙️ Methodology and Key Components
The method employs a gas chromatograph with a Fourier transform infrared spectrometer for detection. A cool on-column injector is used to avoid boiling point discrimination and reduce adsorption. Calibration requires the use of individual aromatic components, and density can be measured per standards D1298 or D4052. The procedure follows standard gas chromatography practices as defined in Practice E355.
📊 Terminology and Safety
Specific terms include “aromatics” for compounds with benzene or naphthalene rings, and “calibrated aromatic component” for individual calibrations. The standard emphasizes safety, relying on general practices from D4175 and E355. Users must establish appropriate safety and environmental practices before application.
⚠️ This method has not been validated by ASTM for refinery process streams such as reformates or FCC naphthas. Users should verify suitability for such applications.
💡 Ensure liquid blends for standards are prepared according to Practice D4307 for accurate calibration.
❓ Frequently Asked Questions
🔍 What is the primary purpose of ASTM D5986-23?
To determine oxygenates, benzene, toluene, C8–C12 aromatics, and total aromatics in finished gasoline via GC/FTIR.
💡 What are the key instrumental requirements?
A gas chromatograph coupled with an FTIR spectrometer, equipped with a cool on-column injector.
⚡ What are the concentration limits for benzene?
Benzene is measured from 0.1 % to 2 % by volume.
📌 Can this method be used for all gasoline blends?
It is designed for finished motor gasoline only and may not be suitable for refinery intermediates without validation.