ASTM D7371 test method for biodiesel content in diesel fuel oil
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)
1. Scope
1.1 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 % (see Note 1). This procedure is applicable only to FAME. Biodiesel in the form of fatty acid ethyl esters (FAEE) will cause a negative bias.

NOTE 1 - Using the proper ATR sample accessory, the range maybe expanded from 1 to 100 volume %, however precision data is not available above 20 volume %.

1.2 The values stated in SI units of measurement are to be regarded as the standard. The values given in parentheses are for information only.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

2. Referenced Documents
2.1 ASTM Standards:
D975 Specification for Diesel Fuel Oils
D976 Test Method for Calculated Cetane Index of Distillate Fuels
D1298 Test Method for Density, Relative Density (Specific Gravity), or API Gravity of Crude Petroleum and Liquid Petroleum Products by Hydrometer Method
D4052 Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density Meter
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D4307 Practice for Preparation of Liquid Blends for Use as Analytical Standards
D4737 Test Method for Calculated Cetane Index by Four Variable Equation
D5854 Practice for Mixing and Handling of Liquid Samples of Petroleum and Petroleum Products
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
D6751 Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels
D7467 Specification for Diesel Fuel Oil, Biodiesel Blend (B6 to B20)
E168 Practices for General Techniques of Infrared Quantitative Analysis
E1655 Practices for Infrared Multivariate Quantitative Analysis
E2056 Practice for Qualifying Spectrometers and Spectro-photometers for Use in Multivariate Analyses, Calibrated Using Surrogate Mixtures

3. Terminology
3.1 Definitions:
3.1.1 biodiesel, n - a fuel comprised of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats, designated B100.

3.1.2 biodiesel blend, BXX, n - a blend of biodiesel fuel with petroleum-based diesel fuel.

3.1.2.1 Discussion - In the abbreviation BXX, the XX represents the volume percentage of biodiesel fuel in the blend.

3.1.3 diesel fuel, n - petroleum-based middle distillate fuel.

3.1.4 multivariate calibration, n - process for creating a model that relates component concentrations or properties to the absorbances of a set of known reference samples at more than one wavelength or frequency.

3.1.4.1 Discussion - The resultant multivariate calibration model is applied to the analysis of spectra of unknown samples to provide an estimate of the component concentration or property values for the unknown sample.

3.1.4.2 Discussion - The multivariate calibration algorithm employed in this test method is partial least square (PLS) as defined in Practices E1655.

3.2 Abbreviations:
ATR = attenuated total reflectance
Bxx = see 3.1.2
FAEE = fatty acid ethyl esters
FAME = fatty acid methyl esters
FTIR = Fourier transform infrared
mid-IR = mid infrared
PLS = partial least square
ULSD = ultra low sulfur diesel