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D5845-21 – Standard Test Method Technical Guide
ASTM D5845-21 is a standard test method for the determination of methanol, ethanol, tert-butanol, methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), and diisopropyl ether (DIPE) in gasoline by infrared spectroscopy. It is applicable to oxygenates in gasoline, singularly or in mixtures, within specified concentration ranges.
📐 Scope and Applicability
This test method covers the determination of the specified oxygenates in gasoline by infrared spectroscopy. The method is suitable for methanol from 1.7 % to 5.5 % by mass, ethanol from 1.5 % to 10 % by mass, tert-butanol from 1.6 % to 12 % by mass, DIPE from 1.2 % to 17 % by mass, MTBE from 2.0 % to 16.4 % by mass, ETBE from 2.0 % to 18.5 % by mass, and TAME from 1.5 % to 18.5 % by mass. The values stated in SI units are standard.
⚙️ Test Procedure and Calibration
The method utilizes infrared spectroscopy combined with multivariate calibration techniques. Practice D8321 is the preferred standard for developing calibration equations, replacing E1655. Sampling must follow Practice D4057, and density measurements can be performed using D1298 or D4052. Calibration blends are prepared per Practice D4307. Note that surrogate methods like D5845 may use multivariate calibration equations but should not claim to follow the procedures fully.
💡 Tip: For accurate results, ensure that calibration standards are prepared following D4307 and that the spectrometer is validated per D8321 for robust multivariate models.
📊 Measured Oxygenate Ranges
The following table lists the concentration ranges for each oxygenate as specified in D5845-21.
| 🟦 Oxygenate | 📏 Mass Percent Range (%) |
|---|---|
| Methanol | 1.7 – 5.5 |
| Ethanol | 1.5 – 10 |
| tert-Butanol | 1.6 – 12 |
| DIPE | 1.2 – 17 |
| MTBE | 2.0 – 16.4 |
| ETBE | 2.0 – 18.5 |
| TAME | 1.5 – 18.5 |
These ranges apply when oxygenates are present singly or in mixtures.
⚠️ Safety: This standard does not address all safety concerns. Users should establish appropriate safety, health, and environmental practices before use.
❓ Frequently Asked Questions
🔍 What oxygenates are covered by D5845?
The standard covers methanol, ethanol, tert-butanol, MTBE, ETBE, TAME, and DIPE in gasoline as determined by infrared spectroscopy.
💡 How does D5845 compare to GC methods?
D5845 is an infrared spectroscopic method, while methods like D4815 and D5599 use gas chromatography. D5845 can provide rapid analysis but requires robust multivariate calibration as per D8321.
⚡ What are the calibration requirements?
Calibration must follow Practice D4307 for blend preparation, and multivariate models should be developed per D8321. Surrogate methods cannot claim full compliance with D8321 procedures.
📌 Can D5845 be used for multiple oxygenates in one sample?
Yes, the method is applicable to oxygenates in gasoline singularly or in mixtures within the specified mass percent ranges.