Detection Target
Determination of Fatty Acid Methyl Esters Content in Middle Distillate Fuels
Overview
This solution conforms to the ASTM D7371 Standard Test Method for Determination of Biodiesel (Fatty Acid Methyl Esters) Content in Diesel Fuel Oil Using Mid Infrared Spectroscopy (FTIR-ATR-PLS Method). This test method covers the determination of the content of fatty acid methyl esters (FAME) biodiesel in diesel fuel oils. It is applicable to concentrations from 1.00 to 20 volume %. It is applicable only to FAME. Biodiesel is a blendstock commodity primarily used as a value-added blending component with diesel fuel. This test method is applicable for quality control in the production and distribution of diesel fuel and biodiesel blends containing FAME.
Principle
Dilute the test sample with cyclohexane to an appropriate concentration and record the mid-infrared absorption spectrum of the prepared sample. Measure the maximum peak absorbance of the characteristic ester absorption band at approximately 1745 ± 5 cm-1. Calculate the FAME content using a calibration formula derived from standard solutions with known FAME concentrations.
Operating Conditions
Apparatus and Accessories
1) HKL-7371 FTIR Spectrometer for FAMEs In Middle Distillates
2) Accessory: Fixed Liquid Cell (KBr or CaF2 material, path length 0.5mm)
Test Parameters
1) Resolution: 4 cm-1
2) Scan times: 32
3) Detector: Pyroelectric Infrared Detector
Reagent and Martials
1) Cyclohexane (purity > 99.5%)
2) Certified FAME standard for calibration
Sample Measurement
1. Preparation of Calibration Solutions
Weigh the calibration FAMEs using an analytical balance and place them into appropriate volumetric flasks. Prepare a series of (no fewer than 5) FAME calibration solutions by adding cyclohexane.
2. Infrared Spectrum Measurement
Inject the calibration solutions into the liquid cell in order from low to high concentration and measure their corresponding infrared spectra. Record the absorbance values at approximately 1745 cm-1.
3. Establishment of Quantitative Model
Establish a linear relationship between the absorbance values at approximately 1745 cm-1 and the corresponding concentrations of the calibration solutions to obtain the quantitative analysis model.
4. Sample Measurement
Measure the infrared absorption spectra of the samples using the same method described in step 2. Record the absorbance values at the characteristic peak position and substitute them into the quantitative model to determine the FAME concentration in the samples.
Conclusion
For fatty acid methyl esters (FAMEs) samples in diesel fuel with volume fractions ranging from approximately 1.7% to 22.7%, the use of infrared spectroscopy for content determination is feasible, and the obtained quantitative data are reliable.