1、Designation: D6756 10Standard Test Method forDetermination of the Red Dye Concentration and Estimationof the ASTM Color of Diesel Fuel and Heating Oil Using aPortable Visible Spectrophotometer1This standard is issued under the fixed designation D6756; the number immediately following the designation
2、 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 () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determin
3、ation of the red dyeconcentration of diesel fuel and heating oil and the estimationof the ASTM color of undyed and red-dyed diesel fuel andheating oil. The test method is appropriate for use with dieselfuel and heating oil of Grades 1 and 2 described in Specifica-tions D396, D975, D2880 and D3699. R
4、ed dye concentrationsare determined at levels equivalent to 0.1 to 20 mg/Lof SolventRed 26 in samples with ASTM colors ranging from 0.5 to 5.The ASTM color of the base fuel of red-dyed samples withconcentration levels equivalent to 0.1 to 20 mg/L of SolventRed 26 is estimated for the ASTM color rang
5、e from 0.5 to 5.The ASTM color of undyed samples is estimated over theASTM color range of 0.5 to 5.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if a
6、ny, 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 ASTM Standards:2D396 Specification for Fuel OilsD975 Specificatio
7、n for Diesel Fuel OilsD1500 Test Method forASTM Color of Petroleum Products(ASTM Color Scale)D2880 Specification for Gas Turbine Fuel OilsD3699 Specification for KerosineD4052 Test Method for Density, Relative Density, and APIGravity of Liquids by Digital Density MeterD4057 Practice for Manual Sampl
8、ing of Petroleum andPetroleum ProductsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD6045 Test Method for Color of Petroleum Products by theAutomatic Tristimulus MethodD6708 Practice for StatisticalAssessment and Improvementof Expected Agreement Between Two Test Methods tha
9、tPurport to Measure the Same Property of a MaterialE203 Test Method for Water Using Volumetric Karl FischerTitrationE1655 Practices for Infrared Multivariate QuantitativeAnalysisE2056 Practice for Qualifying Spectrometers and Spectro-photometers for Use in Multivariate Analyses, CalibratedUsing Surr
10、ogate Mixtures3. Terminology3.1 Definitions:3.1.1 ASTM color, nthe name of an empirical scale ofexpressing the color of a petroleum liquid darker than Sayboltcolor based on a scale of 0.5 (lightest) to 8 Dil (darkest) anddetermined by Test Method D1500.3.1.2 surrogate calibration, na multivariate ca
11、librationthat is developed using a calibration set which consists ofmixtures with pre-specified and reproducible compositions thatcontain substantially fewer chemical components than thesamples which will ultimately be analyzed. E20563.1.3 surrogate method, na standard test method that isbased on a
12、surrogate calibration. E20563.2 Definitions of Terms Specific to This Standard:3.2.1 red dye, nsubstance that, when added to fuel,absorbs green light and imparts a red color to the product. Forthis test method, red dyes are:3.2.1.1 product dyes, nalkyl derivatives of azobenzene-4-azo-2-naphthol (met
13、hyl derivatives of Color Index No. 26105)which are more soluble in diesel fuel.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.05 on Properties of Fuels, Petroleum Coke and Carbon Material.Curre
14、nt edition approved Oct. 1, 2010. Published November 2010. Originallyapproved in 2002. Last previous edition approved in 2009 as D675609a. DOI:10.1520/D6756-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of
15、 ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.1.2 solvent red
16、26, nan azobenzene-4-azo-2-naphtholdye of a specific chemical structure that is used to gage theamount of red dye present in a given sample.4. Summary of Test Method4.1 A sample is introduced into the liquid specimen cell.The cell is placed into the light path of the apparatus. A beamof visible ligh
17、t is imaged through the sample onto a detector,and the detector response is determined. Wavelengths of thespectrum, which correlate highly with the red dye concentra-tion and the ASTM color, are selected for analysis usingselective bandpass filters. A multivariate mathematical modelconverts the abso
18、rption values from the filters to the red dyeconcentration and the estimated ASTM color.5. Significance and Use5.1 In the United States, high sulfur content (defined by theUnited States Environmental Protection Agency (USEPA)middle distillate products and diesel fuel used for off-roadpurposes, other
19、 than aviation turbine fuel, are required bygovernment agencies to contain red dye. The dye concentrationrequired to be present in high sulfur and off-road dieselproducts is regulated by the United States EnvironmentalProtection Agency and the United States Internal RevenueService, respectively.5.2
20、Some fuels that are readily exchanged in the markethave a color specification. The color of the base fuel is maskedby the presence of the red dye. This test method provides ameans of estimating the base color of Number 1 and Number2 diesel fuel and heating oil in the presence of red dye.5.3 The test
21、 method provides a means to indicate conform-ance to contractual and legal requirements.6. Interferences6.1 The presence of colorants other than the hydrocarbonstypical of Number 1 and 2 diesel fuel and heating oils, or thepresence of red dye other than the specified types, can interferewith the acc
22、urate determination of the red dye concentrationreported as Solvent Red 26 equivalent or the base fuel ASTMcolor.7. Apparatus7.1 Filter Spectrophotometer, is equipped with specimenchamber, visible wavelength source, four 10 6 2 nm (fullwidth at half transmission maximum) bandpass wavelengthdiscrimin
23、ating filters having center wavelengths at 450 6 2nm, 520 6 2 nm, 650 6 2 nm, and 700 6 2 nm. The bandpassfilters are used in conjunction with the visible wavelengthsource to produce light in the blue, green, red, and far-redregions of the electromagnetic spectrum. A detector convertsthe transmitted
24、 light to an electronic signal that is processed byan A-D converter and a microprocessor.3,47.2 Specimen Cell, constructed of polymethacrylate or clearoptical glass having a path length of approximately 1 cm. Ifmore than one cell is used for calibration, qualification andsample measurement, the path
25、 length of the cells must bematched to 60.001 cm.8. Sampling8.1 Samples shall be taken in accordance with PracticeD4057 or D4177.8.2 Precautions must be taken to shield the samples fromlight prior to analysis.9. Calibration and Standardization of the Apparatus9.1 The instrument is calibrated accordi
26、ng to the proceduredescribed in Annex A2.NOTE 1The DT100C3instruments are calibrated at the factory by thevendor.9.2 The instrument is qualified according to the proceduredescribed in Annex A3.NOTE 2The DT100C instruments are qualified at the factory by thevendor.9.2.1 If the qualification procedure
27、 is performed by thevendor, then the user shall perform a quality control checkaccording to the procedure described in Section 10.10. Quality Control Check10.1 To confirm the performance of the instrument, periodi-cally measure the red dye concentration and theASTM color ofthree control samples usin
28、g the procedure outlined in Section11. The quality control check standards should be analyzed atleast once a week or before the sample analysis if theinstrument is used less frequently than weekly or if theinstrument is moved to a different laboratory or field location.NOTE 3Quality control samples
29、are available from DT100C3.10.1.1 A standard of known dye concentration and ASTMcolor is made according to the information in A1.4. The set ofquality control samples shall have a low, medium, and high reddye concentration (0 to 14 6 2 mg/L) and a low, medium, andhigh ASTM color (0 to 5 ASTM color un
30、its).10.1.2 The standards are stable for at least one year whenstored in the dark in tightly sealed bottles.10.2 If the red dye concentration determined for one of thequality control samples differs from the known value by morethan 1.0 mg/L or if the estimated ASTM color for one of thequality contro
31、l samples differs from the known value by morethan 0.5 units, then the measurement system is out-of-controland cannot be used to determine the red dye concentration or3DT100C instruments used to develop this precision statement are availablefrom PetroSpec, Inc., 530 Main St., Acton, MA 01720.4The so
32、le source of supply of the apparatus known to the committee at this timeis PetroSpec, Inc. If you are aware of alternative suppliers, please provide thisinformation to ASTM International Headquarters. Your comments will receivecareful consideration at a meeting of the responsible technical committee
33、,1whichyou may attend.D6756 102used to estimate the ASTM color until the cause of theout-of-control behavior is corrected.10.3 If correction of out-of-control behavior requires repairto the instrument or recalibration of the instrument, thequalification of instrument performance described inAnnexA3s
34、hall be performed before the system is used to measure reddye concentration or used to estimate ASTM color.11. Procedure11.1 Prepare the filter spectrophotometer for operation inaccordance with the manufacturers instructions.11.2 Equilibrate the sample to between 20 and 25C.11.3 Without filtering th
35、e sample (see 13.6), fill a clean, dryspecimen cell. The external optical surfaces shall be clean. Ifnot, wipe clean and dry with a piece of lint-free paper (forexample, lens paper).11.4 Insert the specimen cell into the cell chamber of theinstrument.11.5 Record the Solvent Red 26 equivalent concent
36、rationand the estimated ASTM color.12. Report12.1 Report the red dye concentration to the nearest 0.1mg/L as Solvent Red 26 equivalent dye.NOTE 4The number of milligrams per litre of Solvent Red 26equivalents measured by the DT100C instrument is labeled as ppm on thedisplay. The ppm unit reported by
37、 the DT100C instrument is equivalent tomg/L.12.2 Report the estimated ASTM color value as: estimatedASTM color using ASTM D6756. Report the result to thenearest 0.1 color value.12.2.1 The reported estimated ASTM color value can beconverted to a value that mimics the reporting convention ofthe Test M
38、ethod D1500. For estimatedASTM color values thatare x.0 or x.5, the estimated value is reported unchanged. Forestimated color values between x.1 and x.4, round up the valueto the nearest x.5 and place an L before the result. Forestimated color values between x.6 and x.9, round up the valueto the nea
39、rest whole number and place an L before the result.If the estimated color value is greater than 8.0, report theestimated result as 8.13. Precision and Bias513.1 Interlaboratory tests of the procedure were carried outusing sixteen samples covering the red dye concentration rangeequivalent to 0 to 16
40、mg/L of Solvent Red 26 equivalents andcovering the range of ASTM color from 0.5 to 3.0. Sevenlaboratories participated in the interlaboratory tests. The pre-cision of this procedure as determined by the statisticalexamination of the interlaboratory test results is as follows:513.1.1 RepeatabilityThe
41、 difference between successivetest results obtained with the same apparatus under constantoperating conditions on identical samples would in the longrun, in normal and correct operation of the test method, exceedthe following value in only one case in twenty:r 5 0.22 mg/Lfor Solvent Red 26 equivalen
42、t dye concentrations between0.1 and 20.0 mg/L, andr 5 0.085 ASTM color unitsfor samples in the ASTM color range of 0 to 5.13.1.2 ReproducibilityThe difference between two singleand independent results obtained from different instruments onidentical samples, would in the long run, in normal and corre
43、ctoperation of the test method, exceed the following value inonly one case in twenty:R 5 0.86 mg/Lfor Solvent Red 26 equivalent dye concentrations between0.1 and 20.0 mg/L, andR 5 0.20 ASTM color unitsfor samples in the ASTM color range of 0 to 5.13.2 BiasSince there is no accepted reference materia
44、lsuitable for determining the bias for the procedure in this testmethod, bias has not been determined.13.3 Relative Bias (Dye Concentration)Some relativebias,5among certain samples, was observed when the SolventRed 26 concentration results were compared to the expectedSolvent Red 26 concentrations.
45、The bias between the theoreti-cal and measured Solvent Red 26 concentration is observedwith the test samples that were made using Solvent Red 164,the chemical used to commercially dye diesel fuel. Theobserved bias does appear to be of a systematic nature and isnot known to be related to the accuracy
46、 of this test method,since the Solvent Red 26 equivalency of the Solvent Red 164used in sample preparation has not been determined, onlyestimated.13.4 Relative Bias (ASTM Color)Relative bias,5for onesample, was observed when the color results were compared tothe Test Method D1500 results; however, t
47、his bias is near thereproducibility of the test methods and is inconclusive. Theoverall relative bias to Test Method D1500 is not significant.NOTE 5The average bias of the estimatedASTM color relative to TestMethod D1500 was 0.17. The largest average biases, 0.4 to 0.5, wereobserved for four samples
48、 that had an ASTM color of 0.5 and red dyeconcentrations that ranged from 10 to 20 mg/L.13.5 Relative Bias (Unfiltered vs. Filtered Samples)Asingle laboratory analyzed a total of 99 separate split samples(unfiltered vs. filtered) to determine the impact that filteringsamples can have on reported red
49、 dye concentration results.5Based on a Practice D6708 analysis of the results, where theY-method was unfiltered samples and the X-method wasfiltered samples, a bias correction formula of Y = X 0.107was determined. In short, filtering the samples led to astatistically significant bias being determined. As such, toensure testing consistency between laboratories, samples arenot to be filtered as indicated in 11.3. Inclusion of the TestMethod D1500 analysis formula is for information only andnot intended to be used by laboratories as an official offset toapply to
