1、Designation: D5442 93 (Reapproved 2013)D5442 17Standard 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
2、 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. Scope Scope*1.1 This test method covers the quantitative determination of the carbon number distribution of petroleum
3、waxes in the rangefrom n-C17 through n-C44 by gas chromatography using internal standardization. In addition, the content of normal and non-normalhydrocarbons for each carbon number is also determined. Material with a carbon number above n -C44 is determined by itsdifference from 100 100 % by mass %
4、 and reported as C45+.1.2 This test method is applicable to petroleum derived waxes, including blends of waxes. This test method is not applicableto oxygenated waxes, such as synthetic polyethylene glycols (for example, Carbowax2), or natural products such as beeswax orcarnauba.1.3 This test method
5、is not directly applicable to waxes with oil content greater than 10 % as determined by Test Method D721.1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.5 This standard does not purport to address all of the safety conce
6、rns, if any, associated with its use. It is the responsibilityof the user of this standard to consult and establish appropriate safety and health practices and determine the applicability ofregulatory limitations prior to use.1.6 This international standard was developed in accordance with internati
7、onally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3D721 Test M
8、ethod for Oil Content of Petroleum WaxesD4307 Practice for Preparation of Liquid Blends for Use as Analytical StandardsD4626 Practice for Calculation of Gas Chromatographic Response FactorsE260 Practice for Packed Column Gas ChromatographyE355 Practice for Gas Chromatography Terms and Relationships3
9、. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 carbon numbera number corresponding to the number of carbon atoms in a hydrocarbon.3.1.2 cool on-column injectiona sample introduction technique in gas chromatography where the sample is injected inside thefront portion of a parti
10、tion column at a temperature at or below the boiling point of the most volatile component in the sample.3.1.3 low volume connectora metal or glass union designed to connect two lengths of capillary tubing. Usually designed sothat the tubing ends are joined with a minimum of either dead volume or ove
11、rlap between them.3.1.4 non(normal paraffn)hydrocarbon (NON) all other hydrocarbon types excluding those hydrocarbons with carbon atomsin a single length. Includes aromatics, naphthenes, and branched hydrocarbon types.1 This test method is under the jurisdiction ofASTM Committee D02 on Petroleum Pro
12、ducts, Liquid Fuels, and Lubricants and is the direct responsibility of SubcommitteeD02.04.0H on Chromatographic Distribution Methods.Current edition approved May 1, 2013June 1, 2017. Published August 2013July 2017. Originally approved in 1993. Last previous edition approved in 20082013 asD5442 93(2
13、008).(2013). DOI: 10.1520/D5442-93R13.10.1520/D5442-17.2 Carbowax is a registered trademark of Union Carbide Corp.3 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
14、 standards Document Summary page on the ASTM website.This document is not an ASTM standard and 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 acc
15、urately, ASTM recommends that users consult prior editions as appropriate. In all cases only the 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 Harbo
16、r Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.5 normal paraffna saturated hydrocarbon which has all carbon atoms bonded in a single length, without branching orhydrocarbon rings.3.1.6 wall coated open tube (WCOT)a term used to specify capillary columns in which the statio
17、nary phase is coated on theinterior 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 an internal standard are completely dissolved in an appropriate solvent andintroduced i
18、nto a gas chromatographic column that separates the hydrocarbon components by increasing carbon number. Thecolumn temperature is linearly increased at a reproducible rate until the sample is completely eluted from the column.4.2 The eluted components are detected by a flame ionization detector and r
19、ecorded on a strip chart or computer system. Theindividual carbon numbers are identified by comparing the retention times obtained from a qualitative standard with the retentiontimes of the wax sample. The percent of each hydrocarbon number through C44 is calculated via internal standard calculation
20、s afterapplying response factors.4.3 For samples with final boiling points greater than 538C538 C complete elution of all components may not be achievedunder the specified conditions. For this reason, the C45+ material is determined by summing the concentrations of each individualcarbon number throu
21、gh C44 and subtracting this total from 100 mass %.100 % by mass.5. Significance and Use5.1 The determination of the carbon number distribution of petroleum waxes and the normal and non-normal hydrocarbons ineach can be used for control of production processes as well as a guide to performance in man
22、y end uses.5.2 Data resulting from this test method are particularly useful in evaluating petroleum waxes for use in rubber formulations.6. Apparatus6.1 ChromatographAny gas chromatographic instrument that can accommodate a WCOT column, equipped with a flameionization detector (FID), and that can be
23、 operated at the conditions given in Table 1 may be employed. The chromatograph shouldbe equipped with a cool on-column inlet (or equivalent) for introducing appropriate quantities of sample without fractionation. Inaddition, the gas chromatograph must be capable of generating a chromatogram where t
24、he retention times of an individual peakhave retention time repeatability within 0.1 min. 0.1 min. Refer to Practices E260 and E355 for general information on gaschromatography.6.2 Sample Introduction SystemAny system capable of introducing a representative sample onto the front portion of a WCOTcol
25、umn may be employed. Cool on-column injection is preferred, however other injection techniques can be used provided thesystem meets the specification for linearity of response in 9.6. For cool on-column injection, syringes with 0.150.15 mm to0.25-mm0.25 mm outside diameter needles have been used suc
26、cessfully for columns 0.25-mm0.25 mm inside diameter or largerand standard 0.47-mm0.47 mm outside diameter syringe needles have been used for columns 0.53-mm0.53 mm inside diameteror greater.6.2.1 Care must be taken that the sample size chosen does not allow some peaks to exceed the linear range of
27、the detector oroverload the capacity of the column.6.3 Column(s)Any column used must meet the chromatographic resolution specification in 9.5. WCOT columns with 2525 mto 30-m30 m lengths and a stationary phase coating of methyl siloxane or 5 % phenyl methyl siloxane have been successfully used.Cross
28、-linked or bonded stationary phases are preferred.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): 0.25 0.25 0.25Carrier gas: Helium He
29、lium 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(C):380 400 375Sample size (L): 1.0 1.
30、0 1.0D5442 1726.4 RecorderA recording potentiometer or equivalent with a full-scale deflection of 5 mV 5 mV or less for measuring thedetector signal versus time. Full scale response time should be 2 s 2 s or less. Sensitivity and stability should be sufficient togenerate greater than 2-mm2 mm record
31、er deflection for a hydrocarbon injection of 0.05 0.05 % by mass % under the analysisconditions employed.6.5 Integrator or ComputerMeans must be provided for integrating the detector signal and summing the peak areas betweenspecific time intervals. Peak areas can be measured by computer or electroni
32、c integration. The computer, integrator, or gaschromatograph must have the capability of subtracting the area corresponding to the baseline (blank) from the sample area, andhave the ability to draw the baselines used for peak area integration.7. Reagents and Materials7.1 Carrier GasCarrier gas appro
33、priate for the flame ionization detector. Hydrogen and helium have been used successfully.The minimum purity of the carrier gas used should be 99.95 mol %. (Warning Hydrogen and helium are compressed gasesunder high pressure. Hydrogen is an extremely flammable gas.)7.2 n-hexadecaneHydrocarbon to be
34、added to samples as an internal standard. Minimum purity of 98 % is required.7.3 Standards for Calibration and Identification Standard samples of normal paraffins covering the carbon number range(through C44) of the sample are needed for establishing the retention times of the individual paraffins a
35、nd for calibration forquantitative measurements. Hydrocarbons used for standards must be greater than 95 % purity.7.4 SolventA liquid (99 % pure) suitable for preparing a quantitative mixture of hydrocarbons and for dissolving petroleumwax. Cyclohexane has been used successfully. (WarningSolvents ar
36、e flammable and harmful if inhaled.)7.5 Linearity StandardPrepare a weighed mixture of n-paraffins covering the range between n-C16 to n-C44 and dissolve themixture in cyclohexane. Use approximately equal amounts of each of the paraffins and a balance capable of determining mass towithin 1 % of the
37、mass of each compound added. It is not necessary to include every n-paraffin in this mixture so long as the samplecontains n-C16, n-C44, and at least one of every fourth n-paraffin. It will be necessary to prepare the standard sample incyclohexane, so that the normal paraffins are completely dissolv
38、ed in the solvent. Solutions of 0.01 0.01 % by mass % n-paraffinhave been used successfully. This sample must be capped tightly, to prevent solvent loss which will change the concentration ofparaffins in the standard blend.NOTE 1Refer to Practice D4307 for details of how to prepare hydrocarbon mixtu
39、res.7.6 Internal Standard SolutionPrepare a dilute solution of internal standard in cyclohexane in two steps as follows:7.6.1 Prepare a stock solution containing 0.5 0.5 % by mass % n-C16 in cyclohexane by accurately weighing approximately 0.4g 0.4 g n-C16 into a 100 mL 100 mL volumetric flask.Add 1
40、00 mL 100 mL of cyclohexane and reweigh. Record the mass of n-C16to within 0.001 g 0.001 g and the mass of solution (cyclohexane and n-C16) to within 0.l g.0.l g.7.6.2 Prepare a dilute solution of n-C16 internal standard by diluting one part of stock solution with 99 parts of cyclohexane.Calculate t
41、he concentration of internal standard in the dilute solution using Eq 1.CISTD5WISTDWS3100%100 (1)where:where:CISTD = mass % n-C16 internal standard in dilute solution,CISTD = percent by mass n-C16 internal standard in dilute solution,WISTD = weight of n-C16 from 7.6.1,Ws = weight of cyclohexane plus
42、 n-C16 from 7.6.1,100 % = factor to convert weight fraction to mass %, and100 % = factor to convert weight fraction to percent by mass, and100 = dilution factor.8. Sampling8.1 To ensure homogeneity, completely mix the entire wax sample by heating it to 10C10 C above the temperature at whichthe wax i
43、s completely molten and then mix well by stirring. Using a clean eyedropper, transfer a few drops to the surface of a cleansheet of aluminum foil, allow to solidify and break into pieces. The wax can either be used directly as described in Section 11 orplaced in a sealed sample vial until ready for
44、use.8.1.1 Aluminum foil usually contains a thin film of oil from processing. 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
45、 not normally need to beconditioned; however, it is good chromatographic practice to briefly condition a new column as described below.D5442 1739.1.1 Install the column in the chromatographic oven and connect one column end to the sample inlet system.Turn on the sourceof carrier gas and set the flow
46、 controller (or pressure regulator) to the flow rate to be used in the analysis. Increase the columntemperature to the maximum value to be used in the analysis and maintain this temperature for 30 min. 30 min. Cool the columntemperature to room temperature and connect the remaining column end to the
47、 detector. Care must be taken that the columnterminates as close as possible to the tip of the FID jet. The temperature of the column between the column oven and the detectorjet must be maintained above the maximum column temperature.9.2 Operating ConditionsSet the chromatographic operating conditio
48、ns (see Table 1) and allow the system to achieve alltemperature setpoints. The recorder, computer or integrating device should be connected so that a plot of the detector signal versustime can be obtained. Make certain that the FID is ignited before proceeding.9.3 Baseline BlankAfter conditions have
49、 been set to meet performance requirements, program the column temperatureupward to the maximum temperature to be used. Once the column oven temperature has reached the maximum temperature, coolthe column to the selected starting temperature. Without injecting a sample, start the column temperature program, the recordingdevice and the integrator. Make two baseline blank runs to determine if the baseline blank is repeatable. If the detector signal isnot stable or if the baseline blanks are not repeatable, then the column should either be conditi
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