ASTM D7371-07
(Test Method)Standard Test Method for Determination of Biodiesel (Fatty Acid Methyl Esters) Content in Diesel Fuel Oil Using Mid Infrared Spectroscopy (FTIR-ATR-PLS Method)
Standard Test Method for Determination of Biodiesel (Fatty Acid Methyl Esters) Content in Diesel Fuel Oil Using Mid Infrared Spectroscopy (FTIR-ATR-PLS Method)
SIGNIFICANCE AND USE
Biodiesel is a fuel 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.
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.
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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7371 – 07
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 standard is issued under the fixed designation D7371; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D4307 Practice for Preparation of Liquid Blends for Use as
Analytical Standards
1.1 This test method covers the determination of the content
D4737 Test Method for Calculated Cetane Index by Four
of fatty acid methyl esters (FAME) biodiesel in diesel fuel oils.
Variable Equation
It is applicable to concentrations from 1.00 to 20 volume %
D5854 PracticeforMixingandHandlingofLiquidSamples
(see Note 1). This procedure is applicable only to FAME.
of Petroleum and Petroleum Products
Biodiesel in the form of fatty acid ethyl esters (FAEE) will
D6299 Practice for Applying Statistical Quality Assurance
cause a negative bias.
and Control Charting Techniques to Evaluate Analytical
NOTE 1—Using the proper ATR sample accessory, the range maybe
Measurement System Performance
expandedfrom1to100volume %,howeverprecisiondataisnotavailable
D6751 Specification for Biodiesel Fuel Blend Stock (B100)
above 20 volume %.
for Middle Distillate Fuels
1.2 The values stated in SI units of measurement are to be
E168 Practices for General Techniques of Infrared Quanti-
regarded as the standard. The values given in parentheses are
tative Analysis
for information only.
E1655 Practices for Infrared Multivariate Quantitative
1.3 This standard does not purport to address all of the
Analysis
safety concerns, if any, associated with its use. It is the
E2056 Practice for Qualifying Spectrometers and Spectro-
responsibility of the user of this standard to establish appro-
photometers for Use in Multivariate Analyses, Calibrated
priate safety and health practices and determine the applica-
Using Surrogate Mixtures
bility of regulatory limitations prior to use.
3. Terminology
2. Referenced Documents
3.1 Definitions:
2.1 ASTM Standards:
3.1.1 biodiesel, n—afuelcomprisedofmono-alkylestersof
D975 Specification for Diesel Fuel Oils
long chain fatty acids derived from vegetable oils or animal
D976 Test Method for Calculated Cetane Index of Distillate
fats, designated B100. D6751
Fuels
3.1.2 biodiesel blend, BXX, n—a blend of biodiesel fuel
D1298 Test Method for Density, Relative Density (Specific
with petroleum-based diesel fuel.
Gravity), or API Gravity of Crude Petroleum and Liquid
3.1.2.1 Discussion—In the abbreviation BXX, the XX rep-
Petroleum Products by Hydrometer Method
resents the volume percentage of biodiesel fuel in the blend.
D4052 Test Method for Density, Relative Density, and API
D6751
Gravity of Liquids by Digital Density Meter
3.1.3 diesel fuel, n—petroleum-based middle distillate fuel.
D4057 Practice for Manual Sampling of Petroleum and
3.1.4 multivariate calibration, n—process for creating a
Petroleum Products
model that relates component concentrations or properties to
D4177 Practice for Automatic Sampling of Petroleum and
the absorbances of a set of known reference samples at more
Petroleum Products
than one wavelength or frequency. E1655
3.1.4.1 Discussion—The resultant multivariate calibration
This test method is under the jurisdiction of ASTM Committee D02 on
modelisappliedtotheanalysisofspectraofunknownsamples
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
to provide an estimate of the component concentration or
D02.04.0F on Absorption Spectroscopic Methods.
property values for the unknown sample.
Current edition approved Oct. 1, 2007. Published October 2007. DOI: 10.1520/
D7371-07. 3.1.4.2 Discussion—The multivariate calibration algorithm
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
employed in this test method is partial least square (PLS) as
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
defined in Practices E1655.
Standards volume information, refer to the standard’s Document Summary page on
3.2 Abbreviations:
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7371 – 07
TABLE 1 Attenuated Total Reflectance (ATR) Conical
Cells Specification
ATR = attenuated total reflectance
ATR element material ZnSe
Bxx = see 3.1.2
beam condensing optics conical, non-focusing optics
FAEE = fatty acid ethyl esters
integral to cell body
FAME = fatty acid methyl esters
element configuration circular cross section with
coaxial conical ends
FTIR = Fourier transform infrared
cone half angle 60°
mid-IR = mid infrared
element length 36.83 to 39.37 mm (1.45 to 1.55 in.)
PLS = partial least square
element diameter 3.175 mm (0.125 in.)
ULSD = ultra low sulfur diesel
angle of incidence at sample interface 53.8°
maximum range of incidence angles 6 1.5°
standard absorbance 0.38 6 0.02 AU
4. Summary of Test Method -1
(1428 cm band of acetone)
material of construction 316 stainless steel
4.1 A sample of diesel fuel, biodiesel, or biodiesel blend is
A
seals Chemrez or Kalrez o-rings
introduced into a liquid attenuated total reflectance (ATR)
A
Trademarks of Chemrez, Inc. and Dupont Performance Elastomers L.L.C.
sample cell. A beam of infrared light is imaged through the
sample onto a detector, and the detector response is deter-
6.4 Fatty Acid Ethyl Esters (FAEE) Interference—The pres-
mined. Wavelengths of the absorption spectrum that correlate
ence of FAEE in the composition of the biodiesel will result in
highly with biodiesel or interferences are selected for analysis.
an overall lower concentration measurement of biodiesel
A multivariate mathematical analysis converts the detector
content. Outlier statistical results may be a useful tool for
response for the selected areas of the spectrum from an
determining high concentration FAEE content (for additional
unknown to a concentration of biodiesel.
FAEE information, see research report referenced in Section
4.2 This test method uses Fourier transform mid-IR spec-
15).
trometer with an ATR sample cell. The absorption spectrum
6.5 Undissolved Water—Samples containing undissolved
shall be used to calculate a partial least square (PLS) calibra-
water will result in erroneous results. Filter cloudy or water
tion algorithm.
saturated samples through a dry filter paper until clear prior to
their introduction into the instrument sample cell.
5. Significance and Use
5.1 Biodiesel is a fuel commodity primarily used as a 7. Apparatus
value-added blending component with diesel fuel.
7.1 Mid-IR Spectrometric Analyzer:
5.2 This test method is applicable for quality control in the
7.1.1 Fourier Transform Mid-IR Spectrometer—Thetypeof
production and distribution of diesel fuel and biodiesel blends
apparatus suitable for use in this test method employs an IR
containing FAME.
source, a liquid attenuated total internal reflection cell, a
scanning interferometer, a detector, anA-D converter, a micro-
6. Interferences
processor,andamethodtointroducethesample.Thefollowing
performance specifications shall be met:
6.1 The hydrocarbon composition of diesel fuel has a
-1
Scan Range 4000 to 650 cm
significant impact on the calibration model. Therefore, for a
-1
Resolution 4 cm
robust calibration model, it is important that the diesel fuel in
the biodiesel fuel blend is represented in the calibration set. 7.1.2 The noise level shall be established by acquiring a
6.2 Proper choice of the apparatus, design of a calibration single beam spectrum using air or nitrogen. The single beam
matrix, utilization of multivariate calibration techniques, and spectrum obtained can be the average of multiple of FTIR
evaluation routines as described in this standard can minimize scans but the total collection time shall not exceed 60 seconds.
interferences. If interference from water vapor or carbon dioxide is a
6.3 Water Vapor Interference—The calibration and analysis problem, the instrument shall be purged with dry air or
nitrogen.Thenoiseofthespectrumat100 %transmissionshall
bands in A1.2 lie in regions where significant signals due to
-1
water vapor can appear in the infrared spectrum. This shall be be less than 0.3 % in the region from 1765 to 1725 cm .
7.2 Absorption Cell, multi-bounce (multi-reflections) at-
accounted for to permit calibration at the low end concentra-
tions. tenuated total reflectance cell. It shall meet one of the follow-
ing requirements:
NOTE 2—Ideally, the spectrometer should be purged with dry air or
7.2.1 Conical Attenuated Total Reflectance (ATR) Cell,
nitrogen to remove water vapor. The purge should be allowed to stabilize
having similar specifications defined in Table 1. This cell is
over several hours before analytical work is pursued, due to the rapid
suitable for the low, medium, and high concentration ranges.
changes in the air moisture content within the spectrometer during early
stages of the purge. In cases where water vapor prevention or elimination 7.2.2 Horizontal Attenuated Total Reflectance (ATR) Cell,
is not possible using a purge, the operator should measure a reference
with ZnSe element ATR mounted on a horizontal plate. The
-1
background spectrum for correction of the ratioed spectrum for each
absorbance at 1745 cm shall not exceed 1.2 absorbance units
sample spectrum measured. This operation is generally automated in
for the highest concentration calibration standard used in the
today’s spectrometer systems and the operator should consult the manu-
calibrationrange.Therefore,forhigherconcentrationmeasure-
facturer of the spectrometer for specific instructions for implementing
ments, careful consideration of element length and face angle
automated background correction routines. The spectrometer should be
shall be made to maximize sensitivity without exceeding 1.2
sealedanddesiccatedtominimizetheaffectofwatervaporvariations,and
-1
any accessory should be sealed to the spectrometer. absorbance units at 1745 cm .
D7371 – 07
8. Reagents and Materials 9.1.2 Protect samples from excessive temperatures prior to
testing.
8.1 Purity of Reagents—Spectroscopic grade (preferred) or
9.1.3 Donottestsamplesstoredinleakycontainers.Discard
reagent grade chemicals shall be used in tests. Unless other-
and obtain a new sample if leaks are detected.
wise indicated, it is intended that all reagents shall conform to
9.2 Sample Handling During Analysis:
thespecificationsofthecommitteeonanalyticalreagentsofthe
9.2.1 When analyzing samples using the FTIR, the sample
American Chemical Society, where such specifications are
temperature needs to be within the range of 15 to 27°C.
available. Other grades may be used, provided it is first
Equilibrate all samples to the temperature of the laboratory (15
ascertained that the reagent is of sufficiently high purity to
to 27°C) prior to analysis by this test method.
permit its use without lessening the accuracy of the determi-
9.2.2 After analysis, if the sample is to be retained, reseal
nation.
the container before storing.
8.1.1 B100 (Neat Biodiesel)—Used for calibration, qualifi-
cation, and quality control standards shall be compliant with
10. Calibration and Qualification of the Apparatus
Specification D6751. The B100 shall be fatty acid methyl
esters. Soy methyl ester (SME) was used in calibration 10.1 Before use, the instrument needs to be calibrated
standards for developing the precision of this test method. according to the procedure described in Annex A1. This
Esters derived from other feedstocks, for example animal fats,
calibration can be performed by the instrument manufacturer
canola oil, jatropha oil, palm oil, rapeseed oil, and yellow prior to delivery of the instrument to the end user. If, after
grease may be used. Standards made with yellow grease
maintenance, the instrument calibration is repeated, the quali-
methyl esters should not represent more than 50 % of the fication procedure is also repeated.
number of the calibration standards. A BQ-9000 certified
10.2 Before use, the instrument is qualified according to the
producer for the biodiesel is recommended to ensure quality of procedure described inAnnexA1. The qualification need only
product. See Annex A2 for further discussion. be carried out when the instrument is initially put into
8.1.2 Middle Distillate Fuel—Used for calibration, qualifi- operation, recalibrated, or repaired.
cation, and quality control standards shall be compliant with
Specification D975, free of biodiesel or biodiesel oil precursor, 11. Quality Control Checks
or both. As far as possible, middle distillate fuel shall be
11.1 Confirm the in-statistical-control status of the test
representative of petroleum base stocks anticipated for blends
method each day it is used by measuring the biodiesel
to be analyzed (crude source, 1D, 2D, blends, winter/summer
concentration of at least one quality control sample that is
cuts, low aromatic content, high aromatic content, and the
similar in composition and matrix to samples routinely ana-
like). See Annex A2 for calibration set.
lyzed. For details on quality control sample selection, prepa-
8.1.3 Diesel Cetane Check Fuel—Low (DCCF-Low). (See
ration, testing, and control charting, refer to Practice D6299.
A2.2 for alternative material.)
11.2 A system that is found to be out of statistical control
8.1.4 Diesel Cetane Check Fuel—High (DCCF-High).
cannot be used until the root cause(s) of out-of-control is
8.1.5 Diesel Cetane Check Fuel—Ultra High (DCCF-Ultra
identified and corrected.
High).
11.3 If correction of out-of-control behavior requires repair
8.1.6 Acetone [67-64-1]—Reagent grade.
to the instrument or recalibration of the instrument, the
8.1.7 Toluene [108-88-3]—Reagent grade.
qualificationofinstrumentperformancedescribedinA1.3shall
8.1.8 Methanol [67-56-1]—Reagent grade.
be performed before the system is used to measure the
8.1.9 Triple Solvent—Amixtureofequalpartsbyvolumeof
biodiesel content of samples.
toluene, acetone, and methanol.
12. Procedure
9. Sampling and Sample Handling
12.1 Equilibratethesamplestobetween15and27°Cbefore
9.1 General Requirements:
analysis.
9.1.1 Fuel samples to be analyzed by this test method shall
12.2 Clean the sample cell of any residual fuel according to
be sampled using procedures outlined in Practice D4057 or
the manufacturer’s instructions. Remove the fuel by flushing
Practice D4177, where appropriate. Do not use “sampling by
the cell with sufficient solvent or the subsequent sample to
water displa
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.