1、Designation: D4046 11D4046 14Standard Test Method forAlkyl Nitrate in Diesel Fuels by Spectrophotometry1This standard is issued under the fixed designation D4046; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev
2、ision. 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 a procedure for the determination of 0.03 to 0.30 volume % of alkyl nitrate in diesel fuels.1.2 This
3、test method can be used for the determination of any alkyl nitrate in diesel fuel provided that standards used forcalibration contain the same alkyl nitrate ester as the test specimens to be analyzed.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are
4、included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prio
5、r to use. For specific hazard statements, see Section 7.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent Water3. Summary of Test Method3.1 The determination is based on the simultaneous hydrolysis of the ester in 65 % sulfuric acid solution and nitration ofm-xylenol by the
6、nitric acid liberated. The nitroxylenol is extracted from the reaction mixture and reacted with sodium hydroxideto form the yellow salt. The color is measured spectrophotometrically at 452 nm, and the concentration of alkyl nitrate isdetermined by reference to the slope of the calibration curve.4. S
7、ignificance and Use4.1 In diesel fuel, the presence of alkyl nitrates such as amyl nitrate, hexyl nitrate, or octyl nitrate causes a higher residue valuethan observed in untreated fuel, which can lead to erroneous conclusions as to the coke forming propensity of the fuel. Thepresence of such alkyl n
8、itrate in the fuel can be determined using this test method. This test method can be used to determine theamount of alkyl nitrate that has been added to diesel fuel to improve Cetane Number. The test method is applicable as a basis forjudging compliance with specifications covering any alkyl nitrate
9、.5. Interferences5.1 Other nitrate esters, inorganic nitrate ions, and nitrogen oxides will interfere.6. Apparatus6.1 Absorption Cells, matched, having a 1.000 6 0.002-cm path length.6.2 Separatory Funnel, Squibb-type glass stoppered with TFE-fluorocarbon stopcock, 125-mL capacity.6.3 Shaking Machin
10、e, automatic, capable of multiple samples and 250 oscillations/min.6.4 Spectrophotometer, capable of measuring absorption in the region of 452 6 5 nm.6.5 Volumetric Flask, 10- and 100-mL capacity.1 This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products Products, Liqui
11、d Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.03 on Elemental Analysis.Current edition approved June 1, 2011June 1, 2014. Published July 2011July 2014. Originally approved in 1981. Last previous edition approved in 20052011 asD404691(2005).D4046 11. DOI: 10.1520/D4046-1
12、1.10.1520/D4046-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and
13、is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only th
14、e current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States16.6 Measuring Pipet, 1-mL
15、, 3-mL, 4-mL, and 10-mL.6.7 Buret, 10-mL capacity.7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents conform to the specifications of the committee on Analytical Reagents of the American Chemical Society, w
16、here suchspecifications are available.3 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purityto permit its use without lessening the accuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, references to water shall be understo
17、od to mean reagent water conforming toType II of Specification D1193.7.3 Acetic Acid, reagent grade.7.4 Alkyl Nitrate.7.5 Alkyl Nitrate, Standard SolutionPipet 3.0 mL of the alkyl nitrate to be determined into a 100-mL volumetric flask anddilute to volume with diesel fuel.7.6 Diesel Fuel, additive-f
18、ree (WarningFlammable.).7.7 Isooctane (2,2,4-trimethylpentane). (WarningFlammable.).7.8 Isopropyl Alcohol, reagent grade. (WarningFlammable.).7.9 m-Xylenol SolutionsDilute 4 mL of m-xylenol (2,4-dimethylphenol) to 100 mL in acetic acid.7.10 Sodium Hydroxide SolutionDissolve 50 g of sodium hydroxide
19、(NaOH) pellets in 1000 mL of distilled water.7.11 Sulfuric AcidAdd slowly with stirring, 500 mL of nitrate-free sulfuric acid (H2SO4) (rel dens 1.84) to 269 mL of colddistilled water.8. Calibration and Standardization8.1 Carefully measure 1.0, 3.0, 5.0, 8.0, and 10 mL 10 mL of alkyl nitrate standard
20、 solution ( see 7.5) from a buret into eachof five separate 100-mL volumetric flasks and dilute to the mark with diesel fuel.8.2 Measure 1.0-mLportions of each standard into each of five 10-mLvolumetric flasks.To another 10-mLflask add 1.0 mL mLof blank diesel fuel. Dilute all flasks to volume with
21、isopropyl alcohol.8.3 Pipet 1.0 mL of each standard solution (see 8.2) into each of five separate 125-mL separatory funnels. To another funneladd 1.0 mL 1.0 mL of the blank solution. This covers concentrations from 0.03 to 0.30 volume % alkyl nitrate.8.4 Add 1.0 mL of m-xylenol solution (see 7.9) to
22、 each separatory funnel and swirl to mix thoroughly.8.5 Add 40 mL of H2SO4 (see 7.11). The m-xylenol must be added before the sulfuric acid. Otherwise low or negative resultswill be obtained.8.6 Secure the stopper with springs or rubber bands and shake the separatory funnel and its content for 30 mi
23、n on the automaticshaking machine set at fast speed.NOTE 1The amount of contact the sample has with the H2SO4 determines the extent of hydrolysis. Therefore, the speed and time of shaking shouldbe the same for both the samples and the calibration standards.8.7 To each separatory funnel add 25 mL of
24、isooctane.8.8 Shake the separatory funnel for 1 min by hand.Allow the layers to separate and discard the acid (bottom) layer.Add 25 mLof distilled water and again shake for 1 min to wash out residual acid. Discard the water (bottom) layer.8.9 Pipet 10.0 mL of NaOH solution into the separatory funnel
25、, shake for 1 min and allow the phases to separate for at least10 min or when phases separate cleanly (see Note 2). Drain a few drops of the lower phase to rinse the stem and discard. Fill a1-cm absorption cell and read the absorbance at 452 6 5 nm with respect to water.NOTE 2If no color forms, chec
26、k the pH. When the solution is not alkaline, add an additional 10.0 mL of NaOH solution and correct calculations forthe increased solution volume.8.10 Subtract the absorbance of the blank from that of each standard to obtain corrected absorbance values. Calculate the slopeof the curve as follows:Slo
27、pe,C 5A/B (1)3 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed bythe American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United S
28、tates Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.D4046 142where:A = sum of the volume percent alkyl nitrate standards, andB = sum of corrected absorbances.9. Procedure9.1 Pipet 1.0 mL of test specimen into a 10-mL volumetric flask and dilute to volu
29、me with isopropyl alcohol.9.2 Pipet 1.0 mL of the sample test specimen prepared in 9.1 into a 125-mL separatory funnel. To another funnel add 1.0 mLof blank isopropyl alcohol.NOTE 3A more accurate blank would be obtained if the same base stock as the samples diluted with isopropyl alcohol, were used
30、.9.3 Follow steps outlined in 8.4 8.9.NOTE 4If an absorbance is too high, dilute an aliquot of the solution five-fold with blank solution and correct calculations accordingly.9.4 Subtract the absorbance of the blank from the absorbance of the samples and calculate the result using the slope of theca
31、libration curve.Alkyl nitrate,volume%5CD (2)where:C = slope of the calibration curve andD = absorbance of the sample.10. Reporting10.1 Report the results to the nearest 0.01 v%, and indicate that they were obtained using Test Method D4046.11. Precision and Bias411.1 The precision of this test method
32、 as obtained by statistical examination of interlaboratory test results is as follows:11.1.1 RepeatabilityThe difference between successive test results, obtained by the same operator with the same apparatusunder constant operating conditions on identical test material, would in the long run, in the
33、 normal and correct operation of thistest method, exceed the following values only in one case in twenty:0.017 vol %4 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1139.D4046 14311.1.2 ReproducibilityThe difference between
34、 two single and independent results, obtained by different operators working indifferent laboratories on identical test material, would in the long run, in the normal and correct operation of this test method,exceed the following values only in one case in twenty:0.036 vol %11.2 BiasThe bias of this
35、 test method cannot be determined since an appropriate standard reference material containing aknown level of alkyl nitrate in diesel fuel is not available.12. Keywords12.1 alkyl nitrate; diesel fuel; nitroxylanol; spectrophotometrySUMMARY OF CHANGESSubcommittee D02.03 has identified the location of
36、 selected changes to this standard since the last issue(D404691(2005)D4046 11) that may impact the use of this standard. (Approved June 1, 2014.)(1) Added new Section Revised subsection 104.1 on reporting the results.to add more information to Significance and Use.ASTM International takes no positio
37、n respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.
38、This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn.Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM In
39、ternational Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address show
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