1、Designation: D5442 93 (Reapproved 2013)Standard Test Method forAnalysis of Petroleum Waxes by Gas Chromatography1This standard is issued under the fixed designation D5442; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、 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 quantitative determinationof the carbon number distribution of petroleum waxes in therang
3、e from n-C17through n-C44by gas chromatography usinginternal standardization. In addition, the content of normal andnon-normal hydrocarbons for each carbon number is alsodetermined. Material with a carbon number above n -C44isdetermined by its difference from 100 mass % and reported asC45+.1.2 This
4、test method is applicable to petroleum derivedwaxes, including blends of waxes. This test method is notapplicable to oxygenated waxes, such as synthetic polyethyl-ene glycols (for example, Carbowax2), or natural products suchas beeswax or carnauba.1.3 This test method is not directly applicable to w
5、axes withoil content greater than 10 % as determined by Test MethodD721.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use
6、. It is theresponsibility of the user of this standard to consult andestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D721 Test Method for Oil Content of Petroleum WaxesD4307 Practice
7、for Preparation of Liquid Blends for Use asAnalytical StandardsD4626 Practice for Calculation of Gas ChromatographicResponse FactorsE260 Practice for Packed Column Gas ChromatographyE355 Practice for Gas Chromatography Terms and Relation-ships3. Terminology3.1 Definitions of Terms Specific to This S
8、tandard:3.1.1 carbon numbera number corresponding to the num-ber of carbon atoms in a hydrocarbon.3.1.2 cool on-column injectiona sample introduction tech-nique in gas chromatography where the sample is injectedinside the front portion of a partition column at a temperatureat or below the boiling po
9、int of the most volatile component inthe sample.3.1.3 low volume connectora metal or glass union de-signed to connect two lengths of capillary tubing. Usuallydesigned so that the tubing ends are joined with a minimum ofeither dead volume or overlap between them.3.1.4 non(normal paraffn)hydrocarbon (
10、NON) all otherhydrocarbon types excluding those hydrocarbons with carbonatoms in a single length. Includes aromatics, naphthenes, andbranched hydrocarbon types.3.1.5 normal paraffna saturated hydrocarbon which hasall carbon atoms bonded in a single length, without branchingor hydrocarbon rings.3.1.6
11、 wall coated open tube (WCOT)a term used tospecify capillary columns in which the stationary phase iscoated on the interior surface of the glass or fused silica tube.Stationary phase may be cross-linked or bonded after coating.4. Summary of Test Method4.1 Weighed quantities of the petroleum wax and
12、an internalstandard are completely dissolved in an appropriate solvent andintroduced into a gas chromatographic column that separatesthe hydrocarbon components by increasing carbon number.The column temperature is linearly increased at a reproduciblerate until the sample is completely eluted from th
13、e column.4.2 The eluted components are detected by a flame ioniza-tion detector and recorded on a strip chart or computer system.The individual carbon numbers are identified by comparing theretention times obtained from a qualitative standard with the1This test method is under the jurisdiction of AS
14、TM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.04.0H on Chromatographic Distribution Methods.Current edition approved May 1, 2013. Published August 2013. Originallyapproved in 1993. Last previous edition approved in 2008 as D5442 93(2008).DOI
15、: 10.1520/D5442-93R13.2Carbowax is a registered trademark of Union Carbide Corp.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page
16、onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1retention times of the wax sample. The percent of eachhydrocarbon number through C44is calculated via internalstandard calculations after applying response factors.4.3
17、 For samples with final boiling points greater than 538Ccomplete elution of all components may not be achieved underthe specified conditions. For this reason, the C45+material isdetermined by summing the concentrations of each individualcarbon number through C44and subtracting this total from 100mas
18、s %.5. Significance and Use5.1 The determination of the carbon number distribution ofpetroleum waxes and the normal and non-normal hydrocarbonsin each can be used for control of production processes as wellas a guide to performance in many end uses.5.2 Data resulting from this test method are partic
19、ularlyuseful in evaluating petroleum waxes for use in rubber formu-lations.6. Apparatus6.1 ChromatographAny gas chromatographic instrumentthat can accommodate a WCOT column, equipped with a flameionization detector (FID), and that can be operated at theconditions given in Table 1 may be employed. Th
20、e chromato-graph should be equipped with a cool on-column inlet (orequivalent) for introducing appropriate quantities of samplewithout fractionation. In addition, the gas chromatograph mustbe capable of generating a chromatogram where the retentiontimes of an individual peak have retention time repe
21、atabilitywithin 0.1 min. Refer to Practices E260 and E355 for generalinformation on gas chromatography.6.2 Sample Introduction SystemAny system capable ofintroducing a representative sample onto the front portion of aWCOT column may be employed. Cool on-column injection ispreferred, however other in
22、jection techniques can be usedprovided the system meets the specification for linearity ofresponse in 9.6. For cool on-column injection, syringes with0.15 to 0.25-mm outside diameter needles have been usedsuccessfully for columns 0.25-mm inside diameter or largerand standard 0.47-mm outside diameter
23、 syringe needles havebeen used for columns 0.53-mm inside diameter or greater.6.2.1 Care must be taken that the sample size chosen doesnot allow some peaks to exceed the linear range of the detectoror overload the capacity of the column.6.3 Column(s)Any column used must meet the chromato-graphic res
24、olution specification in 9.5. WCOT columns with 25to 30-m lengths and a stationary phase coating of methylsiloxane or 5 % phenyl methyl siloxane have been successfullyused. Cross-linked or bonded stationary phases are preferred.6.4 RecorderArecording potentiometer or equivalent witha full-scale defl
25、ection of 5 mV or less for measuring thedetector signal versus time. Full scale response time should be2 s or less. Sensitivity and stability should be sufficient togenerate greater than 2-mm recorder deflection for a hydrocar-bon injection of 0.05 mass % under the analysis conditionsemployed.6.5 In
26、tegrator or ComputerMeans must be provided forintegrating the detector signal and summing the peak areasbetween specific time intervals. Peak areas can be measured bycomputer or electronic integration. The computer, integrator, orgas chromatograph must have the capability of subtracting thearea corr
27、esponding to the baseline (blank) from the samplearea, and have the ability to draw the baselines used for peakarea integration.7. Reagents and Materials7.1 Carrier GasCarrier gas appropriate for the flameionization detector. Hydrogen and helium have been usedsuccessfully. The minimum purity of the
28、carrier gas usedshould be 99.95 mol %. (Warning Hydrogen and helium arecompressed gases under high pressure. Hydrogen is an ex-tremely flammable gas.)7.2 n-hexadecaneHydrocarbon to be added to samples asan internal standard. Minimum purity of 98 % is required.7.3 Standards for Calibration and Identi
29、fication Standardsamples of normal paraffins covering the carbon number range(through C44) of the sample are needed for establishing theretention times of the individual paraffins and for calibrationfor quantitative measurements. Hydrocarbons used for stan-dards must be greater than 95 % purity.7.4
30、SolventA liquid (99 % pure) suitable for preparing aquantitative mixture of hydrocarbons and for dissolving petro-leum wax. Cyclohexane has been used successfully.(WarningSolvents are flammable and harmful if inhaled.)7.5 Linearity StandardPrepare a weighed mixture ofn-paraffins covering the range b
31、etween n-C16to n-C44anddissolve the mixture in cyclohexane. Use approximately equalamounts of each of the paraffins and a balance capable ofdetermining mass to within 1 % of the mass of each compoundadded. It is not necessary to include every n-paraffin in thismixture so long as the sample contains
32、n-C16, n-C44, and atleast one of every fourth n-paraffin. It will be necessary toprepare the standard sample in cyclohexane, so that the normalparaffins are completely dissolved in the solvent. Solutions of0.01 mass % n-paraffin have been used successfully. Thissample must be capped tightly, to prev
33、ent solvent loss whichwill change the concentration of paraffins in the standard blend.TABLE 1 Typical Operating ConditionsColumn length (m): 25 30 15Column insidediameter (mm):0.32 0.53 0.25Stationary phase: DB-1 RTX-1 DB-5methyl silicone methyl silicone 5 % phenyl methylsiliconeFilm thickness (m):
34、 0.25 0.25 0.25Carrier gas: Helium Helium HeliumCarrier flow (mL/min): 1.56 5.0 2.3Linear velocity (cm/s): 33 35 60Column initialtemperature (C):80 80 80Program rate (C/min): 10 8 5Final temperature (C):380 340 350Injection technique: cool on-column cool on-column cool on-columnDetector temperature(
35、C):380 400 375Sample size (L): 1.0 1.0 1.0D5442 93 (2013)2NOTE 1Refer to Practice D4307 for details of how to preparehydrocarbon mixtures.7.6 Internal Standard SolutionPrepare a dilute solution ofinternal standard in cyclohexane in two steps as follows:7.6.1 Prepare a stock solution containing 0.5 m
36、ass % n-C16in cyclohexane by accurately weighing approximately 0.4 gn-C16into a 100 mL volumetric flask. Add 100 mL ofcyclohexane and reweigh. Record the mass of n-C16to within0.001 g and the mass of solution (cyclohexane and n-C16)towithin 0.l g.7.6.2 Prepare a dilute solution of n-C16internal stan
37、dard bydiluting one part of stock solution with 99 parts of cyclo-hexane. Calculate the concentration of internal standard in thedilute solution using Eq 1.CISTD5WISTDWS3100%100(1)where:CISTD= mass % n-C16internal standard in dilute solution,WISTD= weight of n-C16from 7.6.1,Ws= weight of cyclohexane
38、 plus n-C16from 7.6.1,100 % = factor to convert weight fraction to mass %, and100 = dilution factor.8. Sampling8.1 To ensure homogeneity, completely mix the entire waxsample by heating it to 10C above the temperature at whichthe wax is completely molten and then mix well by stirring.Using a clean ey
39、edropper, transfer a few drops to the surface ofa clean sheet of aluminum foil, allow to solidify and break intopieces. The wax can either be used directly as described inSection 11 or placed in a sealed sample vial until ready for use.8.1.1 Aluminum foil usually contains a thin film of oil fromproc
40、essing. This oil must be removed by rinsing the foil withsolvent such as hexane or mineral spirits, prior to use.9. Preparation of Apparatus9.1 Column ConditioningCapillary columns with bonded(or cross-linked) stationary phases do not normally need to beconditioned; however, it is good chromatograph
41、ic practice tobriefly condition a new column as described below.9.1.1 Install the column in the chromatographic oven andconnect one column end to the sample inlet system. Turn on thesource of carrier gas and set the flow controller (or pressureregulator) to the flow rate to be used in the analysis.
42、Increasethe column temperature to the maximum value to be used in theanalysis and maintain this temperature for 30 min. Cool thecolumn temperature to room temperature and connect theremaining column end to the detector. Care must be taken thatthe column terminates as close as possible to the tip of
43、the FIDjet. The temperature of the column between the column ovenand the detector jet must be maintained above the maximumcolumn temperature.9.2 Operating ConditionsSet the chromatographic operat-ing conditions (see Table 1) and allow the system to achieve alltemperature setpoints. The recorder, com
44、puter or integratingdevice should be connected so that a plot of the detector signalversus time can be obtained. Make certain that the FID isignited before proceeding.9.3 Baseline BlankAfter conditions have been set to meetperformance requirements, program the column temperatureupward to the maximum
45、 temperature to be used. Once thecolumn oven temperature has reached the maximumtemperature, cool the column to the selected starting tempera-ture. Without injecting a sample, start the column temperatureprogram, the recording device and the integrator. Make twobaseline blank runs to determine if th
46、e baseline blank isrepeatable. If the detector signal is not stable or if the baselineblanks are not repeatable, then the column should either beconditioned further or replaced.9.3.1 Baseline BleedObserve the detector response fromthe blank run on the recorder. Some increase in detectorresponse will
47、 be observed at the upper column temperaturesdue to stationary phase bleed. Column bleed is acceptable solong as the duplicate baseline blank analyses are repeatable.The baseline should be a smooth curve, free of any chromato-graphic peaks.9.4 Solvent BlankMake a 1-L injection of the cyclo-hexane so
48、lvent and program the column oven. The solvent is ofsuitable purity if there are no detected peaks within theretention time range over which the wax samples elute.9.5 Column ResolutionCheck the efficiency of the GCcolumn by analyzing, under conditions specified in 10.2,a1-L injection of 0.05 mass %
49、solution of n-C20and n-C24incyclohexane. The column resolution must not be less than 30 ascalculated using Eq 2.R 52d1.699W11W2!(2)where:d = distance (mm) between the peak maxima of n-C20andn-C24,W1 = peak width (mm) at half height of n-C20, andW2 = peak width (mm) at half height of n-C24.9.6 Linearity of ResponseFor quantitative accuracy, detec-tor response must be proportional to the mass of hydrocarboninjected, and the response of the non-normal paraffins isassumed to be equivalent to the response of the n-paraffin withthe same carbon numbe
