1、Designation: D 5442 93 (Reapproved 2008)An American National StandardStandard Test Method forAnalysis of Petroleum Waxes by Gas Chromatography1This standard is issued under the fixed designation D 5442; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e 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 quantitative determinationof the carbon number distributio
3、n of petroleum waxes in therange 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 %
4、 and reported asC45+.1.2 This 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 i
5、s not directly applicable to waxes withoil content greater than 10 % as determined by Test MethodD 721.1.4 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,
6、if any, associated with its use. 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:3D 721 Test Method for Oil Content o
7、f Petroleum WaxesD 4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD 4626 Practice for Calculation of Gas ChromatographicResponse FactorsE 260 Practice for Packed Column Gas ChromatographyE 355 Practice for Gas Chromatography Terms and Rela-tionships3. Terminology3.1 Def
8、initions of Terms Specific to This Standard: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 introductiontechnique in gas chromatography where the sample is injectedinside the front portion of a partition column at a tem
9、peratureat or below the boiling point 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.
10、4 non(normal paraffn)hydrocarbon (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 br
11、anchingor hydrocarbon rings.3.1.6 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 qua
12、ntities of the petroleum wax and 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 sa
13、mple is completely eluted from the 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 the1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum
14、 Products and Lubricants and is the direct responsibility of SubcommitteeD02.04.0H on Chromatographic Distribution Methods.Current edition approved Dec. 1, 2008. Published February 2009. Originallyapproved in 1993. Last previous edition approved in 2003 as D 544293(2003)1.2Carbowax is a registered t
15、rademark 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 onthe ASTM website.1Copyright ASTM International,
16、 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.retention times obtained from a qualitative standard with theretention times of the wax sample. The percent of eachhydrocarbon number through C44is calculated via internalstandard calculations after applying respons
17、e factors.4.3 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 tota
18、l from 100mass %.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 meth
19、od are particularlyuseful 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
20、 employed. The 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 retent
21、ion time repeatabilitywithin 0.1 min. Refer to Practices E 260 and E 355 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, h
22、owever other injection 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 o
23、utside diameter 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 chrom
24、ato-graphic resolution 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 RecorderA recording potentiometer or equivalentwith a
25、 full-scale deflection 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 condition
26、semployed.6.5 Integrator 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 subtract
27、ing thearea corresponding 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 minimu
28、m purity of the carrier gas usedshould be 99.95 mol %. (WarningHydrogen 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 Calibra
29、tion and IdentificationStandardsamples 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
30、 % purity.7.4 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 coveri
31、ng the range between 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 sa
32、mple contains 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 ti
33、ghtly, to prevent solvent loss whichwill change the concentration of paraffins in the standard blend.NOTE 1Refer to Practice D 4307 for details of how to preparehydrocarbon mixtures.TABLE 1 Typical Operating ConditionsColumn length (m): 25 30 15Column insidediameter (mm):0.32 0.53 0.25Stationary pha
34、se: DB-1 RTX-1 DB-5methyl silicone methyl silicone 5 % phenyl methylsiliconeFilm thickness (m): 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):38
35、0 340 350Injection technique: cool on-column cool on-column cool on-columnDetector temperature(C):380 400 375Sample size (L): 1.0 1.0 1.0D 5442 93 (2008)27.6 Internal Standard SolutionPrepare a dilute solution ofinternal standard in cyclohexane in two steps as follows:7.6.1 Prepare a stock solution
36、containing 0.5 mass % 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-
37、C16internal standard bydiluting one part of stock solution with 99 parts of cyclohex-ane. Calculate the concentration of internal standard in thedilute solution using Eq 1.CISTD5WISTDWS3100 %100(1)where:CISTD= mass % n-C16internal standard in dilute solu-tion,WISTD= weight of n-C16from 7.6.1,Ws= wei
38、ght of cyclohexane 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 stirrin
39、g.Using a clean eyedropper, 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 fi
40、lm of oil fromprocessing. 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
41、good chromatographic 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
42、 in the analysis. 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 possi
43、ble to the tip of 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 oper-ating conditions (see Table 1) and allow the system to achieveall temperature setpoints.
44、 The recorder, computer 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 temperatureupw
45、ard to the maximum temperature to be used. Once thecolumn oven temperature has reached the maximum tempera-ture, cool the column to the selected starting temperature.Without injecting a sample, start the column temperatureprogram, the recording device and the integrator. Make twobaseline blank runs
46、to determine if the 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 det
47、ectorresponse will 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 t
48、he cyclohex-ane solvent 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 injecti
49、on of 0.05 mass % solution of n-C20and n-C24incyclohexane. The column resolution must not be less than 30 ascalculated using Eq 2.R 52d1.699W1 1 W2!(2)where:d = distance (mm) between the peak maxima of n-C20and n-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, de-tector response must be proportional to the mass of hydrocar-bon injected, and the response of the non-normal paraffins isassumed to be equivalent to the response of the n-paraffin wi
