1、Designation: D 3348 07An American National StandardStandard Test Method forRapid Field Test for Trace Lead in Unleaded Gasoline(Colorimetric Method)1This standard is issued under the fixed designation D 3348; the number immediately following the designation indicates the year oforiginal adoption or,
2、 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. Scope*1.1 This test method covers and is intended for use in thefield by nontechnical pe
3、ople for the quantitative measurementof lead in unleaded gasoline in the range from 0.01 to 0.10 gPb/U.S. gal (2.64 to 26.4 mg Pb/L). This method applies to allcommercial gasolines and responds to all types of lead alkylsas well as to other organic and inorganic forms of lead.NOTE 1This test method
4、is based on the use of the Mobil Lead TestKit (Fig. 1).NOTE 2This test method is a screening test and is not to be used as areplacement for withdrawn Test Method D3116, withdrawn Test MethodD 3229, or Test Method D 3237.1.2 The values stated in SI units are to be regarded as thestandard. The values
5、given in parentheses are for informationonly.1.3 This standard 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 regula
6、tory limitations prior to use. For specificwarning statements, see Section 7.2. Referenced Documents2.1 ASTM Standards:2D3116 Test Method for Trace Amounts of Lead in Gaso-line3D 3229 Method of Test for Low Levels of Lead in Gasolineby X-Ray Spectrometry3D 3237 Test Method for Lead in Gasoline by At
7、omicAbsorption SpectroscopyD 6299 Practice for Applying Statistical Quality AssuranceTechniques to Evaluate Analytical Measurement SystemPerformanceD 6792 Practice for Quality System in Petroleum Productsand Lubricants Testing Laboratories3. Summary of Test Method3.1 The gasoline is treated with iod
8、ine and tetraethyl am-monium chloride in chloroform and subjected to ultravioletlight. The lead alkyls form water-soluble lead alkyl iodides,which are removed from the gasoline by shaking it with anaqueous ammonium nitrate solution. The aqueous extract isfiltered into a solution of 4-(2-pyridylazo)-
9、resorcinol disodiumsalt (PAR) and ammonium hydroxide. The lead is determinedby measuring its PAR complex colorimetrically at 490 nmusing a previously prepared calibration curve.4. Significance and Use4.1 This test is used to determine trace quantities of lead inunleaded gasoline. Unwarranted amounts
10、 of lead may causedeposits in automotive pollution control equipment and poi-soning of catalytic mufflers.5. Interferences5.1 PAR also reacts with many other metals forming highlycolored complexes. However, none of these are normally foundpresent in a soluble form in gasoline. The following metalswe
11、re found to form colors with PAR and if present mayinterfere to give high results: Fe II, Fe III, Co II, Ni II, Cu II,Zn II, Cd II, Mn II, Sn II, V IV, Pb II, U VI, Ti IV, and the rareearths.6. Apparatus6.1 Ultraviolet Lamp, long wavelength, 3660 , placed in astandard 4-W fluorescent fixture.NOTE 3A
12、 3-min electric timer4,5is connected to the fixture in theprototype kit.6.2 Measuring Block, aluminum, drilled to hold an 18 by150-mm test tube, with a mark at a level equal to 5.0 mL ofliquid in the test tube.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and
13、 Lubricants and is the direct responsibility of SubcommitteeD02.03 on Elemental Analysis.Current edition approved Dec. 1, 2007. Published January 2008. Originallyapproved in 1974. Last previous edition approved in 2003 as D 334898(2003)e1.2For referenced ASTM standards, visit the ASTM website, www.a
14、stm.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.3Withdrawn.4The sole source of supply of the 3min timer known to the committee at thistime is H. M. Rhodes, Avon, CT 06001
15、, Catalog No. 90021.5If you are aware of alternative suppliers, please provide this information toASTM International Headquarters. Your comments will receive careful consider-ation at a meeting of the responsible technical committee,1which you may attend.1*A Summary of Changes section appears at the
16、 end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.3 Colorimeter, Portable, capable of operating at 490 mm.Any equivalent instrument capable of measurement near 514nm (the optimum Pb-PAR complex wavelength) may be
17、 used.6.4 Test Tubes,5,6borosilicate, 18 by 150 mm.6.5 Pipets, glass, dropping, capable of delivering 2.0 mLwith a 2-mL bulb. (WarningGasoline or any of the reagentsmust not come in contact with rubber. If this happens, discardthe bulb and pipet and start again.)6.6 Funnel, plastic, 2 in. in inside
18、diameter.6.7 Filter Paper, ashless, hardened, smooth, very fast, 11.0cm in diameter.NOTE 4Certain filter papers that would allow the organic layer(gasoline/chloroform) to filter through are not acceptable.6.8 Graduated Cylinder, plastic, 10-mL.6.9 Glass Vials,5,7with caps, disposable, 1-oz capacity.
19、7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society, wheresuch specifications are available.8Other grades
20、may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.7.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean distilled water or water ofequal purity.7.3 Am
21、monium Hydroxide (sp gr 0.90)Concentrated am-monium hydroxide (NH4OH).7.4 Ammonium Nitrate Solution (Reagent B)Dissolve15.0 6 0.1 g of ammonium nitrate (NH4NO3) in 750 mL ofwater in a 1-L volumetric flask. Dilute to the mark with water.7.5 Chloroform (CHCl3)(WarningMay be fatal ifswallowed. Harmful
22、if inhaled. May produce toxic vapors ifburned. Chronic or repeated exposure can cause liver or kidney6The sole source of supply of the disposable culture tubes known to thecommittee at this time is Sargent Welch Co., 35 Stern Ave., Springfield, NJ 07081,Catalog No. S-79523K.7The sole source of suppl
23、y of the glass vials known to the committee at this timeis J. W. Wilson Glass Co., 501 S. Park Ave., Linden, NJ 07036, Catalog No. 60957.8Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the
24、 American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.FIG. 1 Mobil Lead Test KitD3348072damage. Harmful if inhaled or swallowed. Carci
25、nogen (animalpositive). Skin and eye irritant. May produce toxic vapors ifburned. See A1.1.)7.6 Disodium Salt of 4-(2-pyridylazo)-Resorcinol Dihydrate(PAR2H2O) (Reagent C) Dissolve 25.0 6 0.1 mg of PAR in750 mL of water in a 1-L volumetric flask. Add 10.0 6 0.1 mLof concentrated NH4OH. Dilute to the
26、 mark with water. Storethis in brown bottles out of direct sunlight or in the dark.(WarningLow results are obtained if the monosodium orunsalted PAR is used in this test. Field experience has shownthat the PAR reagent can deteriorate within two to six months.The PAR reagent should be tested by addin
27、g the reagent to atest tube and determining the percent transmittance. If thepercent transmittance is less than 80 %, the reagent should bediscarded.)7.7 Gasoline, Lead-FreeGasoline containing less than0.05 g Pb/gal (13.0 mg Pb/L). (WarningExtremely flam-mable. Harmful if inhaled. Vapors may cause f
28、lash fire. SeeA1.2.)7.8 Iodine.7.9 Iodine/TEAC/CHCl3Solution (Reagent A)Dissolve1.000 g 6 1 mg of iodine in 75 mL of chloroform (CHCl3)ina 100-mL volumetric flask. Add 1.000 g 6 1 mg of tetraethy-lammonium chloride (TEAC) and mix until dissolved. Diluteto the mark with CHCl3.NOTE 5Solutions describe
29、d in 7.4, 7.6, and 7.9 have been found to bestable for at least 2 months.7.10 Lead StandardsThis method was developed usinglead standards prepared by addition of known amounts ofvarious lead alkyls to blended unleaded gasoline to cover therange of this method.7.11 Tetraethylammonium Chloride Monohyd
30、rate (TEAC).7.12 Quality Control (QC) Sample(s), preferably areportions of one or more gasoline materials or product standardsof known lead content that were not used in the generation ofthe instrument calibration curve. These (QC) samples are to beused to check the validity of the testing process a
31、s described inSection 10. An ample supply of QC sample material shall beavailable for the intended period of use, and must be homoge-neous and stable under the anticipated storage conditions.8. Calibration8.1 Prepare a calibration curve as follows, using at least fourgasoline standards of known lead
32、 content that cover the rangefrom 0.01 to 0.10 g Pb/gal (2.64 to 26.4 mg Pb/L).8.1.1 Rinse the 2-mL graduated pipet three times with thegasoline sample.Add 2.0 mL of the sample to a 1-oz glass vial.Add 2.0 mL of iodine/TEAC/CHCl3solution (ReagentA) fromanother pipet, to the vial containing the gasol
33、ine. Tightly capthe vial.8.1.2 Place the vial on the ultraviolet light and set the timerto give the sample a 3-min exposure.8.1.2.1 (WarningUltraviolet light can be harmful to theeyes.Aprotective shield has been provided in the prototype kit.DO NOT remove it or otherwise defeat its purpose. DO NOTst
34、are at the light.)8.1.3 After exposure, remove and uncap the vial. Measure10.0 mL of ammonium nitrate solution (Reagent B) into the10-mL graduated cylinder. Add this to the vial containing thesample. Recap and shake the vial vigorously for 1 min. (Thetimer in the kit may be used.)8.1.4 Place a clean
35、 18-mm test tube in the aluminummeasuring block. Add 5.0 mL of PAR solution (Reagent C) tothe test tube using the mark on the block such that the upperlevel of liquid in the tube is equal to the mark on the block.Place the plastic funnel in the test tube. Fold a piece of filterpaper and place in the
36、 funnel.8.1.5 When the two layers of liquid in the vial haveseparated (8.1.3), pour the entire contents of the vial inside thefilter paper. The aqueous layer will filter into the test tube; thegasoline/CHCl3layer will remain in the filter paper. Tap thefunnel to add any remaining drops of aqueous so
37、lution to thetest tube. Remove the funnel and discard its contents. Swirl thetest tube gently using a wrist action to obtain a uniform color.NOTE 6The lead-PAR complex formed in 8.1.5 must be measuredwithin 10 min after starting 8.1.5.NOTE 7A few drops of the organic layer may come through the filte
38、rpaper. This will not alter the results and can therefore be tolerated.However, if more than 10 drops do come through, refilter the aqueouslayer through a fresh filter paper into a clean empty test tube.NOTE 8Swirling may cause air bubbles to be trapped in the liquid.Wait for these to settle before
39、continuing. Wipe the test tube off with aclean towel to remove any fingerprints that may be present on the surfaceof the tube.8.2 Zero and standardize the colorimeter as follows:8.2.1 Set the colorimeter at 490 nm. Set zero absorbance(100 % transmittance) with water in an 18-mm test tube. Readand re
40、cord the absorbance (or percent transmittance) obtainedfor the standards.8.2.2 Plot the absorbance values versus concentration onrectangular coordinate paper. (If percent transmittance valuesare used, plot them versus concentration using semilog paper,with the percent transmittance values on the log
41、 scale.) Draw abest fit line by eye. (See Fig. 2 and Fig. 3 for examples.) Whenplotting absorbance versus concentration note that the curvedoes not pass through the origin.9. Procedure9.1 Prepare the sample in accordance with the directionsgiven in 8.1.1-8.1.5.NOTE 9Short form instructions are outli
42、ned in Appendix X1.9.2 Place the test tube containing the water in the colorim-eter and set the absorbance to zero, or to 100 % transmittance.9.3 Place the sample in the colorimeter and read theabsorbance or percent transmittance.NOTE 10Time LimitThe PAR-lead solution obtained for the samplein 9.1 m
43、ust be read within 10 min after the step described in 8.1.5.9.4 From the calibration curve, find the lead content of thesample. Determine the lead content to the nearest 0.001 g/gal(0.26 mg/L) value. Report the lead content to 0.01 g/gal (2.64mg/L).NOTE 11The lead content may be obtained from the ca
44、libration curveto three significant figures (0.001 g/gal); however, the value must berounded to two significant figures (0.01 g/gal) for reporting purposes.When the third digit is 5 the value should be rounded to the nearest evennumber. For example, 0.035 g/gal would be reported as 0.04 g/gal, while
45、D3348073FIG. 2 Graph of Transmittance Values Versus ConcentrationFIG. 3 Graph of Absorbance Values Versus ConcentrationD33480740.045 g/gal would also be reported as 0.04 g/gal.10. Quality Control10.1 Confirm the performance of the apparatus or theprocedure, or both, each day it is in use by analyzin
46、g a QCsample (7.12) that is representative of samples typicallyanalyzed. Increase the analysis frequency of the QC sample ifa large number of samples are analyzed. Analysis of theresult(s) from the QC sample(s) can be carried out usingcontrol charts,9or other statistically equivalent techniques, toa
47、scertain the control status of the total testing process. Any outof control data should trigger investigation for root cause. TheQC sample precision shall be checked against the ASTMmethod precision to ensure data quality. Further guidance onquality control can be found in Practices D 6299 and D 679
48、2.11. Precision11.1 The precision of this test method as determined bystatistical examination of interlaboratory test results is asfollows:11.1.1 RepeatabilityThe difference between two test re-sults, obtained by the same operator with the same apparatusunder constant operating conditions on identic
49、al test material,would in the long run, in the normal and correct operation ofthe test method, exceed the following values only in one casein twenty:0.01 g/gal (2.64 mg/L)11.1.2 ReproducibilityThe difference between two singleand independent results obtained by different operators work-ing in different laboratories on identical test material would, inthe long run, in the normal and correct operation of the testmethod, exceed the following values only in one case intwenty:0.02 g/gal (5.28 mg/L)12. Keywords12.1 field test; trace lead; unleaded gasolineAN
