# ASTM D7058-04 (Reapproved 2014)

Designation: D7058 − 04 (Reapproved 2014)Standard Test Method forDetermination of the Red Dye Concentration and Estimationof Saybolt Color of Aviation Turbine Fuels and KerosineUsing a Portable Visible Spectrophotometer1This standard is issued under the fixed designation D7058; the number immediately following 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 (´) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the red dyeconcentration of aviation turbine fuel and kerosine and theestimation of the Saybolt color of undyed and red dyed(0.180 mg/L).The bias for the base fuels was within the standard error of TestMethod D156.13.5 The precision statements in 13.1 were derived from the1997 interlaboratory test program. Participants analyzed sevensets of undyed base fuels and 13 sets of dyed base fuel/colorcombinations in duplicate in the Saybolt color range of –16 to+30 and dye concentration from 0 to 0.374 mg/L, sevenlaboratories participated with the automatic apparatus and fivelaboratories participated with the manual Test Method D156apparatus.514. Keywords14.1 aviation turbine fuel; kerosine; red dye concentration;Saybolt color; visible spectrometryANNEXES(Mandatory Information)A1. PROCEDURE FOR PREPARATION OF RED DYE/SAYBOLT COLOR STANDARDS, QUALIFICATION SAMPLES,AND QUALITY CONTROL SAMPLESA1.1 ScopeA1.1.1 This annex is a description of the preparation of dyeconcentration and color standard samples used for calibrationand qualification. It also describes the preparation of possiblestandard samples that can be used for periodic checks.A1.2 ApparatusA1.2.1 Spectrophotometer, equipped to measure the absor-bance of solutions in the spectral region from 380 to 780 nmwith an effective spectral slit width of 10 6 2nmor56 1 nm.Wavelength measurements shall be repeatable and known to be5Supporting data, results of the 1997 Interlaboratory Cooperative Test Program,have been filed at ASTM International Headquarters and may be obtained byrequesting Research Report RR:D02-1521.TABLE A1.1 Dye Solution Absorption RangeDye Solution Wavelength (nm) AbsorptionYellow 5GS-EX 395 0.881 to 0.935Orange EX 465 0.519 to 0.541Blue SB 600 0.412 to 0.438645 0.465 to 0.494D7058 − 04 (2014)3accurate to 0.1 nm. The photometric linearity is to be 60.5 %of full scale and a photometric reproducibility of 60.2 %.A1.2.2 Sample Cells, constructed of optical glass or quartzhaving a path length of 1 6 0.001 cm for use with thespectrophotometer described in A1.2.1.A1.2.3 Filter Spectrophotometer, see 7.1.A1.2.4 Sample Cell, see 7.2. For use with the spectropho-tometer described in A1.2.3.A1.2.5 Balance, with a readability of 0.1 mg, or better.A1.2.6 Pipettes, 0.5 mL, 1 mL, and 2 mL capacity, Class A.A1.2.7 Volumetric Flasks, 100 mL, 200 mL, and 250 mLcapacity, Class A.A1.2.8 Beaker, 50 mL capacity.A1.3 ReagentsA1.3.1 Purity of Reagents—Reagent grade chemicals shallbe used in all tests. Unless other wise indicated, it is intendedthat all reagents conform to the specifications of the Committeeon Analytical Reagents of the American Chemical Societywhere such specifications are available.6Other grades may beused, provided it is first asserted that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.A1.3.2 Dyes:A1.3.2.1 3-Methyl-1-(phenyl azo)-pyrazol-5-ol (Yellow5GS-EX), with CAS Registry No. 4314-14-1.A1.3.2.2 1-(phenyl azo)-2-naphthalenol (Orange EX), withCAS Registry No. 842-07-9.A1.3.2.3 1,4 bis (butylamino)-9,10-anthracenedione (BlueSB), with CAS Registry No. 17354-14-2.A1.3.2.4 1-[[2,5-dimethyl-4[(2-methylphenyl)azo]phenyl]azo]-2-naphthol (Solvent Red 26), with CAS Registry no.4477-79-6.A1.3.3 1,1-bis(3,4-dimethylphenyl)ethane, (90 % min pu-rity).A1.3.4 Dodecane, anhydrous (99 % min purity).A1.3.5 Xylenes, A.C.S. reagent grade.A1.4 Preparation Procedure for the Saybolt StandardSamplesA1.4.1 Measure 0.2500 6 0.0005 g of Yellow 5GS-EX intoa 50 mL beaker and dissolve the dye in 20 mL of 1,1-bis(3,4-dimethylphenyl)ethane. Quantitatively transfer the Yellow5GS- EX solution to a 250-mL volumetric flask, dilute to themark with 1,1-bis(3,4-dimethylphenyl)ethane and mix well.This solution is called the Yellow 5GS-EX dye solution.A1.4.2 Repeat the above procedure for the Orange EX andBlue SB dyes. These solutions are called Orange EX dyesolution and Blue SB dye solution, respectively.A1.4.3 Pipet 2 mL of the Yellow 5GS-EX solution into a200 mL volumetric flask, dilute to the mark with dodecane andmix well. Using separate flasks repeat this procedure with theOrange EX dye solution and the Blue SB dye solution.A1.4.4 At the wavelengths indicated in TableA1.1, measurethe absorbance of these solutions using the spectrophotometerand cells described in A1.2.1 and A1.2.2, respectively. Usedodecane as the reference material. If the measured absor-bances are not within the indicated ranges, adjust the solutioneither by adding more of the solid dye if the measuredabsorbances are less than the indicated absorbance range or byadding more 1,1-bis(3,4-dimethylphenyl)ethane if the mea-sured absorbances exceed the indicated absorbance range.A1.4.5 If the dye solutions meet the criteria of Table A1.1,then weigh 30.000 6 0.010 g of the Yellow 5GS-EX dyesolution, 10.000 6 0.005 g of Orange EX dye solution and1.000 6 0.001 g of Blue SB dye solution into a 100 mL amberglass bottle. Weigh 45.000 6 0.001 g of dodecane into thesame bottle and mix well. This solution is called the Sayboltcolor mixed dye solution.6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.TABLE A1.2 Indicated Dye Mixture Masses (g) for Synthesis ofCalibration StandardsSamplesSayboltNumberAmount of theSaybolt ColorMixed DyeSolution (g)Amount of the SolventRed 26 Solution1 30 0.200 ± 0.001 0.0002 25 0.472 ± 0.002 0.0003 19 1.087 ± 0.002 0.0004 15 1.724 ± 0.003 0.0005 12 2.083 ± 0.004 0.0006 0 4.545 ± 0.005 0.0007 -15 8.772 ± 0.010 0.0008 30 0.200 ± 0.001 0.0509 25 0.472 ± 0.002 0.05010 19 1.087 ± 0.002 0.05011 15 1.724 ± 0.003 0.05012 12 2.083 ± 0.004 0.05013 0 4.545 ± 0.005 0.05014 -15 8.772 ± 0.010 0.05015 30 0.200 ± 0.001 0.10016 25 0.472 ± 0.002 0.10017 19 1.087 ± 0.002 0.10018 15 1.724 ± 0.003 0.10019 12 2.083 ± 0.004 0.10020 0 4.545 ± 0.005 0.10021 -15 8.772 ± 0.010 0.10022 30 0.200 ± 0.001 0.20023 25 0.472 ± 0.002 0.20024 19 1.087 ± 0.002 0.20025 15 1.724 ± 0.003 0.20026 12 2.083 ± 0.004 0.20027 0 4.545 ± 0.005 0.20028 -15 8.772 ± 0.010 0.20029 30 0.200 ± 0.001 0.50030 25 0.472 ± 0.002 0.50031 19 1.087 ± 0.002 0.50032 15 1.724 ± 0.003 0.50033 12 2.083 ± 0.004 0.50034 0 4.545 ± 0.005 0.50035 -15 8.772 ± 0.010 0.500D7058 − 04 (2014)4A1.4.6 Prepare the Solvent Red 26 solution by weighing0.0750 6 0.0005 g of Solvent Red 26 into a 250 mLvolumetricflask, diluting to the mark with xylenes and mixing well.Calculate the concentration of the solution as follows:Ci5 ~W/0.250! (A1.1)where:Ci= concentration Solvent Red 26 solution in mg/L, andW = weight mass of the solid Solvent Red 26 in mg.A1.4.7 To generate the color standard samples, weigh theamount of the Saybolt color mixed dye solution and theSolvent Red 26 solution specified in Table A1.2 into a 250 mLvolumetric flask, dilute to the mark with dodecane, and mixwell. Calculate the concentration of the Solvent Red 26 in thecolor standard samples as follows:C 5 Ci·W/~d·250! (A1.2)where:C = concentration Solvent Red 26 in the color standardsample, mg/L,Ci= concentration of Solvent Red 26 solution from A1.4.6,W = weight mass of the Solvent Red 26 solution fromA1.4.6,g,andd = density at 15.6°C of the xylenes mixture using TestMethod D4052.A1.4.8 The Saybolt color values assigned to the calibrationsamples listed in Table A1.2 can be confirmed using the devicedescribed in either Test Method D156 or D6045,orthetristimulus method described in Annex X2.2 of Test MethodD6045. Use the samples (1–6) detailed in Table A1.2 that donot contain Solvent Red 26 for the Saybolt color determination.A2. PROCEDURE FOR CALIBRATION OF THE APPARATUSA2.1 ScopeA2.1.1 This annex describes the procedure for calculatingthe model for determining the Solvent Red 26 equivalents andthe model for estimating Saybolt color.A2.2 TerminologyA2.2.1 multivariate calibration—a process for creating acalibration model in which multivariate mathematics is appliedto correlate the absorbances measured for a set of calibrationsamples to reference component concentrations or propertyvalues for the set of samples.A2.2.1.1 Discussion—The multivariate calibration model isapplied to the analysis of spectra of unknown samples toprovide an estimate of the component concentration or prop-erty value for the unknown sample.A2.2.1.2 Discussion—The multivariate calibration algo-rithm used in this test method to calculate the model isMultilinear Regression (MLR).A2.2.2 calibration transfer—a process for transferring thecalibration model from one master instrument to one or moresubject instruments using multivariate regression techniques.A2.3 Calibration of the ApparatusA2.3.1 Calibration Matrix—Prepare calibration standardsin accordance with the information in A1.4.A2.3.2 Calibration—Using the filter spectrophotometer de-scribed in 7.1, acquire the absorption values for each of thecalibration solutions listed in Table A1.2.A2.3.2.1 Use MLR to develop a calibration model based onthe correlation of the set of calibration sample absorbances atthe three wavelengths listed in 7.1 to the known Solvent Red26 dye concentration by fitting to the following set of simul-taneous equations:Ci5 a1·x1,i1…1an·xn,i1e (A2.1)where:Ci= the calculated red dye concentration, mg/L, of the ithcalibration sample from A1.4.7 and Table A1.2,an= the regression coefficient for the absorbance at the nthoptical filter,xn,i= the absorbance at the nth optical filter for the ithcalibration sample, ande = the intercept.NOTE A2.1—Consult Practices E1655 and the references therein for anexplanation of MLR calculation.A2.3.2.2 Use MLR to develop a calibration model based onthe correlation of the set of calibration sample absorbances atthe three wavelengths listed in 7.1 to the known Saybolt colorby fitting to the following set of simultaneous equations:Saybolti5 b1·x1,i1…1bn·xn,i1e (A2.2)where:Saybolti= the Saybolt color of the ith calibration samplefrom Table A1.2,bn= the regression coefficient for the absorbance at thenth optical filter,xn,i= the sample absorbance at the nth optical filter forthe ith calibration sample, ande = the intercept.NOTE A2.2—Consult Practices E1655 and the references therein for anexplanation of MLR calculation.A2.4 Calibration TransferA2.4.1 Follow the procedure described in A1.4.1 andA1.4.3 to synthesize a series of six transfer solutions by using0.300, 0.200, 0.100, 0.050, and 0.025 g ofYellow 5GS-EX dye.A2.4.2 Repeat the procedure from A2.4.1 using Blue SB,and Red 5B-SP dyes.A2.4.3 Acquire the absorbance values for each solutiongenerated in A2.4.1 and A2.4.2 using the master instrumentand the subject instrument.D7058 − 04 (2014)5A2.4.4 Use MLR to calculate a model for each filter thattransforms the subject instrument absorbance into the masterinstrument absorbance.A2.4.5 The red dye concentration model and the Sayboltcolor estimation model calculated for the master instrument areused with the transformed subject instrument absorbancevalues to perform the analyses using the subject instrument.A3. PROCEDURE FOR THE QUALIFICATION OF THE APPARATUSINTRODUCTIONOnce a calibration has been established, the calibrated instrument shall be qualified to ensure thatthe instrument accurately and precisely measures red dye concentration and estimates the Sayboltcolor.A3.1 ScopeA3.1.1 This annex describes the qualification procedure forthe apparatus.A3.2 Qualification of Instrument PerformanceA3.2.1 Prepare at least 12 qualification samples accordingto the procedures described in A1.4. These qualificationsamples shall be similar to, but not the same as, the mixturesestablished for the calibration samples. Prepare the qualifica-tion samples such that the red dye concentration and theSaybolt color spans at least 95 % of the calibration range.NOTE A3.1—The qualification procedure was developed before thePractice E2056 was written and this procedure does not completelyconform to the requirements of Practice E2056.A3.2.2 Use the procedure described in Section 12 to deter-mine the Solvent Red 26 equivalent dye concentration and theestimated Saybolt color for each of the qualification samples.A3.2.3 For each of the surrogate qualification samples,calculate the difference, di, between the measured red dyeconcentration, ŷ, and the red dye concentration calculated fromthe preparation of the sample, y. Calculate the average, d¯,ofthedifference values, di.A3.2.4 The Standard Error of Qualification, SEQsurrogate,iscalculated as:SEQsurrogate5!(i51q~yˆi2 yi!2q(A3.1)A3.2.4.1 The variable q is the number of qualificationsamples used for the red dye concentration measurement.A3.2.5 Calculate the Student’s t value using Eq A3.2.t 5 UdH=q 2 1SEQsurrogateU (A3.2)A3.2.6 Repeat the calculations described in A3.2.3, A3.2.4,and A3.2.5 using the estimated Saybolt color results.A3.2.7 Compare both t values to the critical t value for n–1degrees of freedom. If either of the t values is greater than thecritical t value, then there is a 95 % probability that the resultsare biased, and the instrument is not qualified to perform thetest. Have maintenance performed on the instrument and repeatthe calibration and qualification procedures as required.A3.2.8 Compare the standard error of qualification to thepooled error of qualification calculated for the instruments usedin the test method’s round robin.A3.2.8.1 For the red dye concentration, calculate an F valueby dividing (SEQsurrogate)2by 0.005. Compare the result to thecritical F value for q degrees of freedom in the numerator and67 degrees of freedom in the denominator. If the calculated Fvalue is greater than the critical F value (Table A3.2), theinstrument is not qualified to estimate the red dye concentra-tion. Have maintenance performed on the instrument andrepeat the calibration and qualification procedures, as required.If the calculated F value for the red dye is less than the criticalF value, the instrument is qualified to determine the red dyeconcentration.A3.2.8.2 For the Saybolt color, calculate an F value bydividing (SEQsurrogate)2by 0.88. Compare the result to thecritical F value for q degrees of freedom in the n