1、Designation: D 6229 06Standard Test Method forTrace Benzene in Hydrocarbon Solvents by Capillary GasChromatography1This standard is issued under the fixed designation D 6229; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 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 the determination by capillarygas chromatography of trace benzene in hydrocarbon solvent
3、sat levels from 1.0 to 2400 vppm.NOTE 1Lower levels of benzene may be determined by this testmethod. However the gas chromatography (GC) will have to be modifiedfrom those specified in this test method. The precision of the method maynot apply to these lower benzene levels.1.2 For hazard information
4、 and guidance, see the suppliersMaterial Safety Data Sheet.1.3 The values stated in SI units are to be regarded as thestatement. The values in parenthesis are given for informationonly and are not necessarily the exact equivalent of the SI unitvalues.1.4 For purposes of determining conformance of an
5、 ob-served or a calculated value using this test method to relevantspecifications, test result(s) shall be rounded off “to the nearestunit” in the last right-hand digit used in expressing thespecification limit, in accordance with Practice E 29.1.5 This standard does not purport to address all of th
6、esafety 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 ASTM Standards:2D 4367 Test Method for Benz
7、ene in Hydrocarbon Solventsby Gas ChromatographyE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE 300 Practice for Sampling Industrial Chemicals2.2 ASTM Adjuncts:D2PP Determination of Precision and Bias Data33. Summary of Test Method3.1 A given volum
8、e of the sample is introduced into a gaschromatograph equipped with two capillary columns con-nected in series by switching valve. The specimen passes firstthrough a short capillary column with a bounded nonpolarphase where the components are separated by boiling point.After octane has eluted from t
9、he first column, the componentsheavier than octane are back-flushed to vent. The octane andlighter components then pass through a second capillarycolumn with bounded polar phase where the aromatic andnonaromatic components are separated. The eluted compo-nents are detected by a flame ionization dete
10、ctor, and the peakareas are integrated electronically. The concentration of ben-zene is calculated by a data processor using a response factordetermined by external standard technique.4. Significance and Use4.1 This test method is similar to Test Method D 4367 withthe exception that capillary column
11、s are used and intended fortrace level of benzene in hydrocarbon solvents. The need fortrace benzene analysis in hydrocarbon solvents arose becauseof the increase of more stringent regulation of benzene level inthese materials.5. Apparatus5.1 ChromatographAny gas chromatographic instrumentthat has a
12、 backflush system operated by a switching valveautomatically, flame ionization detector, and can be operated atthe conditions given in Table 1.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility
13、ofSubcommittee D01.35 on Solvents, Plasticizers, and Chemical Intermediates.Current edition approved April 1, 2006. Published April 2006. Originallyapproved in 1998. Last previous edition approved in 2001 as D 6229 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact AS
14、TM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from ASTM International Headquarters. Order Adjunct No.ADJD6300.1*A Summary of Changes section appears at the end of this standard.C
15、opyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 DetectorThe flame ionization detector shall havesufficient sensitivity to detect 0.1 vppm of benzene at a peakheight of 3 times the noise level.5.3 Columnsone 2m (6.5ft), 0.53 mm insi
16、de diameterfused silica capillary with 5-m thick bounded methyl siliconecolumn and one 30m (98.5ft), 0.53-mm inside diameterfused silica capillary with 0.5-m thick bounded polyethyleneglycol column.5.4 Switching ValveA 6port switching valve 175C (347F) maximum temperature, housed in a separate, temp
17、erature-controlled oven, that can be activated automatically by the gaschromatograph.5.5 Sample Inlet SystemThe sample inlet system shall becapable of split injection typically at a 1:10 split ratio.NOTE 2An auto injector was used in the generation of the repeatabil-ity value of this test method, an
18、d is recommended. Manual injection witha syringe is acceptable; however, the observed precision may not apply.5.6 Data Acquisition System:5.6.1 RecorderA 0 to 1 mv range recorder or equivalent,with a full-scale response time of 2 s shall be used.5.6.2 IntegratorMeans shall be provided for determinin
19、gthe area of the benzene peak. This can be done by means of anelectronic integrator or a computer based chromatography datasystem. The integrator/computer system shall have standardchromatographic software for determining the retention timesand areas of eluting peaks.5.7 Microsyringe5 L capacity.5.8
20、 Pipetsmeasuring 1 and 2 mL, graduated in 0.01 mL:5, 10, and 20 mL capacity.5.9 Pipetsdelivery 0.5, 1, 2, 5, 10, 25 mL capacity.5.10 Flasksvolumetric, 25, 50, 100, and 500 mL capacity.6. Reagents6.1 Purity of ReagentsAll reagents shall be reagent gradechemicals with a minimum purity of 99 + mol %.6.
21、1.1 Benzene.6.1.2 n-Hexane, benzene-free.6.1.3 n-Octane, benzene-free.6.1.4 n-Nonane, benzene-free.7. Sampling7.1 Take samples of solvents to be analyzed by this testmethod using the procedures described in Practice E 300.8. Preparation and Conditioning of Capillary Columns8.1 Both columns prescribe
22、d by this procedure shall beobtained ready to use from reputable chromatographic suppli-ers.8.2 Columns shall be conditioned following column sup-plier recommended procedures before use.9. Preparation of Gas Chromatograph9.1 Connect columns A and B to the 6port switching valveby referring to Fig. 1.
23、9.1.1 Adjust the operating conditions to those listed in Table1, but do not turn on the detector. Check the system for leaks.9.2 Adjust the column flow rate as follows:9.2.1 Set the switching valve in the forward flow mode (Fig.2 (a) and adjust the flow controller to give the required columnflow rat
24、e.9.2.2 Set the switching valve in the backflush mode (Fig. 2(b) and check that the column flow is as required.9.2.3 Turn on the detector. Change the switching from theforward flow to the backflush mode several times and observethe baseline. There shall be no baseline shift resulting from thepressur
25、e surge when the switching valves are changed. (Apersistent drift indicates leaks somewhere in the system).9.3 Determine the backflush activation time. The backflushactivation time varies for each column system and shall bedetermined experimentally as follows:9.3.1 Prepare a solution of 0.1 v % noct
26、ane and 0.1 v %nnonane in benzene-free nhexane. With the system in theforward flow mode, introduce 1L of the noctane/nnonane innhexane mixture. Allow the chromatogram to run until thennonane has eluted from the second column and the chro-matographic trace has returned to baseline. Measure the time i
27、nminutes from the injection until the signal goes back tobaseline after the noctane peak. At this point all of thenoctane but essentially none of the nnonane shall haveeluted. One half of the measured time approximates the time tobackflush (see 9.3.3).NOTE 3Some minor adjustment of the backflush act
28、ivation time maybe necessary for some samples.9.3.2 Repeat the run, including the injection of thenoctane/nnonane in a nhexane mixture, but switching thesystem to the backflush mode at the determined backflushactivation time. This should result in a chromatogram showingonly nhexane and noctane, with
29、 little or no nnonaneevident.9.3.3 If necessary, make additional runs, adjusting thebackflush activation time until a chromatogram of all thenoctane (evidenced by a repeatable and constant area count)and little or none of the nnonane is obtained. The establishedbackflush activation time for a partic
30、ular type of sample shallbe used in all subsequent calibration and analysis.TABLE 1 Instrument Conditions Found Satisfactory forMeasuring Trace Concentrations of Benzene in HydrocarbonSolventsGC Parameter ValuesDetector Flame ionization detector (FID)Columns:Length, m (A) 2; (B) 30Inside diameter, m
31、m (A) 0.53; (B) 0.53Liquid phase, bonded (A) methyl silicone; (B) polyethylene glycolLiquid phase thickness (A) 5 m; (B) 0.5 mSwitching value temperature 150C (302F)Temperature programme:Initial temperature 40C (104F)Initial time hold 8 minRamp rate 20C (68F)/minFinal temperature 200C (392F)Final ti
32、me hold 5 minSample size 1 LSplit ratio 1:10Column flow (He carrier gas) 5.0 mL/minBackflush to vent activation time 3.0 minD6229062FIG. 1 Columns Connections to Switching ValveFIG. 2 Flow Switching SystemD622906310. Calibration and Standardization10.1 5000 vppm Stock SolutionPrepare a 5000-vppmbenz
33、ene in nhexane stock solution by accurately delivering0.50 mL of 99+ % purity benzene into a 100mL volumetricflask by means of a delivery pipet. Dilute to the mark withnhexane. This stock solution can be used to prepare variouslevels of benzene in nhexane by accurately diluting therequired volume of
34、 this solution with nhexane in a volumetricflask.10.2 Calibration Standard SolutionPrepare a 10.0 vppmbenzene in nhexane calibration standard solution by accu-rately delivering 1.0 mL of the 5000 vppm stock solution intoa 500mL volumetric flask. Dilute to the mark with nhexane.This calibration stand
35、ard can be used in calibrate the procedureby external standard technique.10.3 CalibrationIf the system has not been used for atleast 12 h, condition the system by running the GC methodonce without injecting any sample. After conditioning, intro-duce 1 L of the 10 vppm benzene in nhexane calibrations
36、tandard by the recommended injection technique and allowthe run to be completed. Determine the response factor for thebenzene peak by means of the integrator/data system. Theresponse factor can also be calculated manually by using thefollowing equation:Rr5 Cb/ Ab(1)where:Rf= the response factor for
37、benzene in vppm per unit area,Cb= the concentration of benzene in the calibration stan-dard in vppm, andAb= the area of the benzene peak in the calibrationstandard.10.4 Adjust the detector sensitivity in such a way that 3times the noise level is equivalent to a benzene concentrationof at least 0.1 v
38、ppm.NOTE 4The repeatability reported for this test method was deter-mined from data generated by a single point, external standard calibrationwith a 10 vppm benzene in nhexane standard solution. If so desired,multipoint calibration can be done by preparing various levels of benzenein nhexane and the
39、 data can be used to generate a calibration curve.NOTE 5Linearity of the benzene response has been confirmed from 1vppm to 2400 vppm.11. Procedure11.1 If the system has not been used for at least 12 h,condition the system by running the GC method once withoutinjecting any sample. After conditioning,
40、 introduce 1 L of the0.1 v % noctane and 0.1 v % nnonane in nhexane mixture(9.3.1) or any sample that requires analysis of trace levelbenzene. Identify the retention time for benzene in the chro-matogram, and determine the area of the benzene peak using anelectronic integrator/data system. A typical
41、 chromatogram of asample containing non-aromatics, benzene, and toluene isshown in Fig. 3.12. Calculation12.1 Using the software of the data system and the responsefactor obtained in 10.3 calculate the benzene concentration (invppm) in the sample corresponding to the peak area determinedin 11.1. Man
42、ual calculation can be done by using the followingequation:Cx5 Rf3 Ax(2)where:Cx= the benzene concentration in the sample in vppm,Rf= the response factor determined in 10.3, andAx= the area of the benzene peak in the sample.12.2 If the results are desired on a weight basis, convertvppm to wppm as fo
43、llows:Benzene, wppm 5Cx/ D! 3 0.8844 (3)where:Cx= the benzene concentration in the sample in vppm,D = the relative density of the sample at 15.6/15.6C(60/60F), and0.8844 = the relative density of benzene at 15.6/15.6C(60/60F).13. Report13.1 Report the concentration of benzene in the sample tothe nea
44、rest 0.1 vppm. or 0.1 wppm.14. Precision and Bias14.1 PrecisionThe following criteria should be used tojudge the acceptability (95 % confidence level) of the resultsobtained by this test method. The criteria were derived from aninterlaboratory study4involving six samples having benzenelevels from 1
45、to 500 vppm, run in duplicate in threelaboratories. The data were statistically evaluated by the D2PPsoftware3used by D02 Committee.14.1.1 RepeatabilityThe repeatability of this test methodis dependent on the benzene level, and is given by the equation:Repeatability r! 5 0.0076X113.30!1.32vppm (4)wh
46、ere X is the benzene level.14.1.2 ReproducibilityThe reproducibility of this testmethod is dependent on the benzene level, and is given by theequation:Reproducibility R! 5 0.032X113.30!1.32vppm (5)where X is the benzene level.14.2 Table 2 gives examples of calculated repeatability andreproducibility
47、 for various levels of benzene, using Eq 4 andEq 5.4Supporting Data are available from ASTM International Headquarters. RequestRR:D011122.TABLE 2 Calculated Precision for Various Benzene LevelBenzene (vppm) Repeatability (r) Reproducibility (R)5 0.4 1.510 0.5 2.120 0.8 3.350 1.8 7.7100 3.9 16.6200 9
48、.0 38.2500 28.6 121.8D6229064FIG.3TypicalChromatogramD622906514.3 BiasBias cannot be determined for this test methodbecause there is no available material having an acceptedreference value.15. Keywords15.1 benzene content; capillary GC; gas chromatography;hydrocarbon solventsSUMMARY OF CHANGESCommit
49、tee D01.35 has identified the location of selected changes to this standard since the last issue(D 6229 01) that may impact the use of this standard. (Approved April 1, 2006.)(1) Added reference to Practice E29in the scope section. (2) Added Practice E29to list of Referenced Standards.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determinat
