1、Designation: D 7371 07An American National StandardStandard Test Method forDetermination of Biodiesel (Fatty Acid Methyl Esters)Content in Diesel Fuel Oil Using Mid Infrared Spectroscopy(FTIR-ATR-PLS Method)1This standard is issued under the fixed designation D 7371; the number immediately following
2、 the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method cov
3、ers the determination of the contentof 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) willcause a negative bias.NO
4、TE 1Using the proper ATR sample accessory, the range maybeexpanded from 1 to 100 volume %, however precision data is not availableabove 20 volume %.1.2 The values stated in SI units of measurement are to beregarded as the standard. The values given in parentheses arefor information only.1.3 This sta
5、ndard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1
6、ASTM Standards:2D 975 Specification for Diesel Fuel OilsD 976 Test Method for Calculated Cetane Index of Distil-late FuelsD 1298 Test Method for Density, Relative Density (SpecificGravity), or API Gravity of Crude Petroleum and LiquidPetroleum Products by Hydrometer MethodD 4052 Test Method for Dens
7、ity and Relative Density ofLiquids by Digital Density MeterD 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD 4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD 4737 Test Method
8、for Calculated Cetane Index by FourVariable EquationD 5854 Practice for Mixing and Handling of LiquidSamples of Petroleum and Petroleum ProductsD 6299 Practice for Applying Statistical Quality AssuranceTechniques to Evaluate Analytical Measurement SystemPerformanceD 6751 Specification for Biodiesel
9、Fuel Blend Stock(B100) for Middle Distillate FuelsE 168 Practices for General Techniques of Infrared Quanti-tative AnalysisE 1655 Practices for Infrared Multivariate QuantitativeAnalysisE 2056 Practice for Qualifying Spectrometers and Spectro-photometers for Use in Multivariate Analyses, CalibratedU
10、sing Surrogate Mixtures3. Terminology3.1 Definitions:3.1.1 biodiesel, na fuel comprised of mono-alkyl esters oflong chain fatty acids derived from vegetable oils or animalfats, designated B100. D 67513.1.2 biodiesel blend, BXX, na blend of biodiesel fuelwith petroleum-based diesel fuel.3.1.2.1 Discu
11、ssionIn the abbreviation BXX, the XX rep-resents the volume percentage of biodiesel fuel in the blend.D 67513.1.3 diesel fuel, npetroleum-based middle distillate fuel.3.1.4 multivariate calibration, nprocess for creating amodel that relates component concentrations or properties tothe absorbances of
12、 a set of known reference samples at morethan one wavelength or frequency. E 16553.1.4.1 DiscussionThe resultant multivariate calibrationmodel is applied to the analysis of spectra of unknown samplesto provide an estimate of the component concentration orproperty values for the unknown sample.1This
13、test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.04.0F on Absorption Spectroscopic Methods.Current edition approved Oct. 1, 2007. Published October 2007.2For referenced ASTM standards, visit the ASTM w
14、ebsite, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United S
15、tates.3.1.4.2 DiscussionThe multivariate calibration algorithmemployed in this test method is partial least square (PLS) asdefined in Practices E 1655.3.2 Abbreviations:ATR = attenuated total reflectanceBxx = see 3.1.2FAEE = fatty acid ethyl estersFAME = fatty acid methyl estersFTIR = Fourier transf
16、orm infraredmid-IR = mid infraredPLS = partial least squareULSD = ultra low sulfur diesel4. Summary of Test Method4.1 A sample of diesel fuel, biodiesel, or biodiesel blend isintroduced into a liquid attenuated total reflectance (ATR)sample cell. A beam of infrared light is imaged through thesample
17、onto a detector, and the detector response is deter-mined. Wavelengths of the absorption spectrum that correlatehighly with biodiesel or interferences are selected for analysis.A multivariate mathematical analysis converts the detectorresponse for the selected areas of the spectrum from anunknown to
18、 a concentration of biodiesel.4.2 This test method uses Fourier transform mid-IR spec-trometer with an ATR sample cell. The absorption spectrumshall be used to calculate a partial least square (PLS) calibra-tion algorithm.5. Significance and Use5.1 Biodiesel is a fuel commodity primarily used as ava
19、lue-added blending component with diesel fuel.5.2 This test method is applicable for quality control in theproduction and distribution of diesel fuel and biodiesel blendscontaining FAME.6. Interferences6.1 The hydrocarbon composition of diesel fuel has asignificant impact on the calibration model. T
20、herefore, for arobust calibration model, it is important that the diesel fuel inthe biodiesel fuel blend is represented in the calibration set.6.2 Proper choice of the apparatus, design of a calibrationmatrix, utilization of multivariate calibration techniques, andevaluation routines as described in
21、 this standard can minimizeinterferences.6.3 Water Vapor InterferenceThe calibration and analysisbands in A1.2 lie in regions where significant signals due towater vapor can appear in the infrared spectrum. This shall beaccounted for to permit calibration at the low end concentra-tions.NOTE 2Ideally
22、, the spectrometer should be purged with dry air ornitrogen to remove water vapor. The purge should be allowed to stabilizeover several hours before analytical work is pursued, due to the rapidchanges in the air moisture content within the spectrometer during earlystages of the purge. In cases where
23、 water vapor prevention or eliminationis not possible using a purge, the operator should measure a referencebackground spectrum for correction of the ratioed spectrum for eachsample spectrum measured. This operation is generally automated intodays spectrometer systems and the operator should consult
24、 the manu-facturer of the spectrometer for specific instructions for implementingautomated background correction routines. The spectrometer should besealed and desiccated to minimize the affect of water vapor variations, andany accessory should be sealed to the spectrometer.6.4 Fatty Acid Ethyl Este
25、rs (FAEE) InterferenceThe pres-ence of FAEE in the composition of the biodiesel will result inan overall lower concentration measurement of biodieselcontent. Outlier statistical results may be a useful tool fordetermining high concentration FAEE content (see ASTMResearch Report RR: D02-16243).6.5 Un
26、dissolved WaterSamples containing undissolvedwater will result in erroneous results. Filter cloudy or watersaturated samples through a dry filter paper until clear prior totheir introduction into the instrument sample cell.7. Apparatus7.1 Mid-IR Spectrometric Analyzer:7.1.1 Fourier Transform Mid-IR
27、SpectrometerThe type ofapparatus suitable for use in this test method employs an IRsource, a liquid attenuated total internal reflection cell, ascanning interferometer, a detector, an A-D converter, a micro-processor, and a method to introduce the sample. The followingperformance specifications shal
28、l be met:Scan Range 4000 to 650 cm-1Resolution 4 cm-17.1.2 The noise level shall be established by acquiring asingle beam spectrum using air or nitrogen. The single beamspectrum obtained can be the average of multiple of FTIRscans but the total collection time shall not exceed 60 seconds.If interfer
29、ence from water vapor or carbon dioxide is aproblem, the instrument shall be purged with dry air ornitrogen. The noise of the spectrum at 100 % transmission shallbe less than 0.3 % in the region from 1765 to 1725 cm-1.7.2 Absorption Cell, multi-bounce (multi-reflections) at-tenuated total reflectanc
30、e cell. It shall meet one of the follow-ing requirements:7.2.1 Conical Attenuated Total Reflectance (ATR) Cell,having similar specifications defined in Table 1. This cell issuitable for the low, medium, and high concentration ranges.3Supporting data have been filed at ASTM International Headquarters
31、 and maybe obtained by requesting Research Report RR: D02-1624.TABLE 1 Attenuated Total Reflectance (ATR) ConicalCells SpecificationATR element material ZnSebeam condensing optics conical, non-focusing opticsintegral to cell bodyelement configuration circular cross section withcoaxial conical endsco
32、ne half angle 60element length 36.83 to 39.37 mm (1.45 to 1.55 in.)element diameter 3.175 mm (0.125 in.)angle of incidence at sample interface 53.8maximum range of incidence angles 6 1.5standard absorbance(1428 cm-1band of acetone)0.38 6 0.02 AUmaterial of construction 316 stainless steelseals Chemr
33、ez or Kalrez o-ringsAATrademarks of Chemrez, Inc. and Dupont Performance Elastomers L.L.C.D73710727.2.2 Horizontal Attenuated Total Reflectance (ATR) Cell,with ZnSe element ATR mounted on a horizontal plate. Theabsorbance at 1745 cm-1shall not exceed 1.2 absorbance unitsfor the highest concentration
34、 calibration standard used in thecalibration range. Therefore, for higher concentration measure-ments, careful consideration of element length and face angleshall be made to maximize sensitivity without exceeding 1.2absorbance units at 1745 cm-1.8. Reagents and Materials8.1 Purity of ReagentsSpectro
35、scopic grade (preferred) orreagent grade chemicals shall be used in tests. Unless other-wise indicated, it is intended that all reagents shall conform tothe specifications of the committee on analytical reagents of theAmerican Chemical Society, where such specifications areavailable.4Other grades ma
36、y be used, provided it is firstascertained that the reagent is of sufficiently high purity topermit its use without lessening the accuracy of the determi-nation.8.1.1 B100 (Neat Biodiesel)Used for calibration, qualifi-cation, and quality control standards shall be compliant withSpecification D 6751.
37、 The B100 shall be fatty acid methylesters. Soy methyl ester (SME) was used in calibrationstandards for developing the precision of this test method.Esters derived from other feedstocks, for example animal fats,canola oil, jatropha oil, palm oil, rapeseed oil, and yellowgrease may be used. Standards
38、 made with yellow greasemethyl esters should not represent more than 50 % of thenumber of the calibration standards. A BQ-9000 certifiedproducer for the biodiesel is recommended to ensure quality ofproduct. See Annex A2 for further discussion.8.1.2 Middle Distillate FuelUsed for calibration, qualifi
39、-cation, and quality control standards shall be compliant withSpecification D 975, free of biodiesel or biodiesel oil precursor,or both. As far as possible, middle distillate fuel shall berepresentative of petroleum base stocks anticipated for blendsto be analyzed (crude source, 1D, 2D, blends, wint
40、er/summercuts, low aromatic content, high aromatic content, and thelike). See Annex A2 for calibration set.8.1.3 Diesel Cetane Check FuelLow (DCCF-Low).5(SeeA2.2 for alternative material.)8.1.4 Diesel Cetane Check FuelHigh (DCCF-High).8.1.5 Diesel Cetane Check FuelUltra High (DCCF-UltraHigh).8.1.6 A
41、cetone 67-64-1Reagent grade.8.1.7 Toluene 108-88-3Reagent grade.8.1.8 Methanol 67-56-1Reagent grade.8.1.9 Triple SolventAmixture of equal parts by volume oftoluene, acetone, and methanol.9. Sampling and Sample Handling9.1 General Requirements:9.1.1 Fuel samples to be analyzed by this test method sha
42、llbe sampled using procedures outlined in Practice D 4057 orPractice D 4177, where appropriate. Do not use “sampling bywater displacement.” FAME is more water-soluble than thehydrocarbon base in a biodiesel blend.9.1.2 Protect samples from excessive temperatures prior totesting.9.1.3 Do not test sam
43、ples stored in leaky containers. Discardand obtain a new sample if leaks are detected.9.2 Sample Handling During Analysis:9.2.1 When analyzing samples using the FTIR, the sampletemperature needs to be within the range of 15 to 27C.Equilibrate all samples to the temperature of the laboratory (15to 27
44、C) prior to analysis by this test method.9.2.2 After analysis, if the sample is to be retained, resealthe container before storing.10. Calibration and Qualification of the Apparatus10.1 Before use, the instrument needs to be calibratedaccording to the procedure described in Annex A1. Thiscalibration
45、 can be performed by the instrument manufacturerprior to delivery of the instrument to the end user. If, aftermaintenance, the instrument calibration is repeated, the quali-fication procedure is also repeated.10.2 Before use, the instrument is qualified according to theprocedure described in Annex A
46、1. The qualification need onlybe carried out when the instrument is initially put intooperation, recalibrated, or repaired.11. Quality Control Checks11.1 Confirm the in-statistical-control status of the testmethod each day it is used by measuring the biodieselconcentration of at least one quality co
47、ntrol sample that issimilar in composition and matrix to samples routinely ana-lyzed. For details on quality control sample selection, prepa-ration, testing, and control charting, refer to Practice D 6299.11.2 A system that is found to be out of statistical controlcannot be used until the root cause
48、(s) of out-of-control isidentified and corrected.11.3 If correction of out-of-control behavior requires repairto the instrument or recalibration of the instrument, thequalification of instrument performance described inA1.3 shallbe performed before the system is used to measure thebiodiesel content
49、of samples.12. Procedure12.1 Equilibrate the samples to between 15 and 27C beforeanalysis.12.2 Clean the sample cell of any residual fuel according tothe manufacturers instructions. Remove the fuel by flushingthe cell with sufficient solvent or the subsequent sample toensure complete washing. For difficult to remove substanceslike B100, precede flushing with triple solvent. Evaporate theresidual solvent with either dry air or nitrogen.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestio
