1、Designation: D 7059 04e1An American National StandardStandard Test Method forDetermination of Methanol in Crude Oils byMultidimensional Gas Chromatography1This standard is issued under the fixed designation D 7059; the number immediately following the designation indicates the year oforiginal adopti
2、on or, 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.e1NOTECorrected Figs. 9 and 10 editorially in October 2004.1. Scope1.1 This test meth
3、od covers the determination of methanolin crude oils by direct injection multidimensional gas chroma-tography in the concentration range of 15 to 900 ppm (m/m).The pooled limit of quantification (PLOQ) is 15 ppm (m/m).1.2 This test method is applicable only to crude oils con-taining less than or equ
4、al to 0.1 % (v/v) water.1.3 This test method has not been tested with crude oilsamples that are solid or waxy, or both, at ambient tempera-tures.1.4 The values stated in SI units are to be regarded asstandard. Alternate units, in common usage, are also providedto increase clarity and aid the users o
5、f this test method.1.5 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 regulatory limitations prior to
6、use.2. Referenced Documents2.1 ASTM Standards:2D 4006 Test Method for Water in Crude Oil by DistillationD 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD 4928 Test Method for Water in Crude Oils by C
7、oulom-etric Karl Fischer TitrationD 6596 Practice for Ampulization and Storage of Gasolineand Related Hydrocarbon Materials3. Terminology3.1 Definitions:3.1.1 analytical column, na CP-Lowox3wall coated opentubular (WCOT) column containing an oxygenates-selectivegas chromatographic liquid phase, used
8、 to further separatemethanol and 1-propanol for quantification.3.1.2 cool-on-column injector, nan injection port thatallows controlled injection of the sample at a temperature closeto or lower than the boiling point of the solvent into the gaschromatographic column or a liner within the injection po
9、rtconnected to the column.3.1.2.1 DiscussionAfter the injection, the injection port isheated at a fixed rate to a temperature sufficiently high enoughto allow the transfer of sample components of interest from theinjection port to the part of the column located in the gaschromatograph (GC) oven.3.1.
10、3 electronic pressure control, nelectronic pneumaticcontrol of carrier gas flows. It can be flow or pressureprogrammed to speed up elution of components.3.1.4 low-volume connector, na special union for con-necting two lengths of tubing 1.6-mm inside diameter andsmaller; sometimes referred to as a ze
11、ro dead-volume union.3.1.5 pre-column, na polydimethylsiloxane WCOT col-umn used to isolate the methanol and 1-propanol and severallight hydrocarbons from the higher boiling portion of the crudeoil sample for transfer to the analytical column for furtherseparation and quantification.3.1.6 programmab
12、le temperature vaporizer (PTV), natemperature programmable injector similar to a cool-on-column injector except that the sample is injected cool into aglass liner or insert instead of the WCOT (3.1.5) column andthen the temperature is programmed in a manner similar to theon-column injector.3.1.6.1 D
13、iscussionThe liner may be replaced, as neces-sary, to remove non-volatile materials. This injector may beoperated in low split mode or direct (no splitting) mode.3.1.7 split/splitless injector, na heated capillary inlet orsample introduction system that allows controlled splitting of1This test metho
14、d is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.04 on Hydrocarbon Analysis.Current edition approved July 1, 2004. Published July 2004.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcont
15、act ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The sole source of supply of the apparatus known to the committee at this timeis Varian-Chrompack, Netherlands. If you are aware of alte
16、rnative suppliers, pleaseprovide this information to ASTM International Headquarters. Your comments willreceive careful consideration at a meeting of the responsible technical committee1,which you may attend.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 194
17、28-2959, United States.the injected sample into two unequal portions, the smaller ofwhich goes to the capillary column, and the greater to a vent.3.1.7.1 DiscussionWhen the vent is closed, the entiresample enters the capillary column and the inlet is operated asa splitless injector. When the vent is
18、 open, the inlet is operatedin the split mode and only a portion of the sample reaches thecapillary column. The ratio of the split between the capillarycolumn and the vent is calculated as described in 3.1.7.2.3.1.7.2 split ratio, nin capillary gas chromatography, theratio of the total flow of carri
19、er gas to the sample inlet versusthe flow of the carrier gas to the capillary column, expressedby:split ratio 5 S 1 C!/C (1)where:S = flow rate at the splitter vent, andC = flow rate at the column outlet.4. Summary of Test Method4.1 An internal standard, 1-propanol, is added to the sample,which is t
20、hen introduced into a gas chromatograph equippedwith two columns and a flow switching system between thetwo columns. The sample first passes through the polydimeth-ylsiloxane WCOT column that performs a pre-separation of themethanol and 1-propanol and eliminates unwanted hydrocar-bons. The methanol
21、and 1-propanol are transferred to theanalytical CP-Lowox column. While the methanol and1-propanol are eluting from the CP-Lowox analytical column,auxiliary carrier gas is used to elute higher boiling crude oilhydrocarbons from the pre-column, either in the forward orbackflush mode, to yield a stable
22、 baseline for the next analysis.5. Significance and Use5.1 Methanol is used in production of crude oil to preventformation of gas hydrates. The presence of residual methanolin crude oils can lead to costly problems in refinery operations.6. Apparatus6.1 ChromatographA multidimensional two-WCOT col-u
23、mn gas chromatographic system, capable of adequately re-solving methanol and the 1-propanol internal standard and ofeliminating hydrocarbon and other interferences, is requiredfor this analysis. Flow switching between the two specifiedWCOT columns may be accomplished by either using a valveor pneuma
24、tic (pressure) switching to redirect flows. Theunwanted higher boiling hydrocarbons may be removed fromthe pre-column either by forward flush or backward flush. Thesystem requires that carrier gas flow controllers must becapable of precise control for the typical pressures required.Such flow control
25、lers are available on gas chromatographs.The precision of this test method was obtained using severalinstrument configurations described in 6.1.1-6.1.5. Other mul-tidimensional configurations may be used, provided that theymeet all of the requirements of this test method.6.1.1 Configuration ACool-on
26、-column injection (no back-flush of pre-column) with two separate selective heartcuts forthe methanol and 1-propanol internal standard. The chromato-graphic instrument can be operated at the approximate condi-tions given in Table 1 and Fig. 1. Figs. 2-5 give chromatogramsand a calibration curve.6.1.
27、2 Configuration BHeated split injection with a singleheartcut of methanol, 1-propanol and several C9minus hydro-carbons transferred to the CP-Lowox WCOT column using asix-port valve. The pre-column, located in a separate auxiliaryoven, is backflushed to a vent using the six-port valve. Table 2and Fi
28、g. 6 give details of the configuration.6.1.3 Configuration CHeated split injection with a singleheartcut for the methanol, 1-propanol and C9minus hydrocar-bons, followed by backflush of the pre-column through theinjection port to remove the high boiling hydrocarbons retainedon the pre-column. The ch
29、romatographic instrument can beoperated at the approximate conditions given in Table 3 andTABLE 1 Operating Conditions for Configuration AInjector On-column. Temperature program: 50C (0.1 min) 30C/min to300C until end of oven program; 1.0 microlitre injected withautosamplerOven temperature program 4
30、0C at 2C/min to 70C (0 min); 4C/min to 190C; 30C/min to250C (13.0 min)Detectors Two flame ionization detectors (FID) at 325C. Hydrogen at 30 mL/min; air at 300 mL/min; helium make-up gas at 30 mL/minColumns 60 m 3 0.53 mm ID 5.0 m film polydimethylsiloxane (pre-column)10 m 3 0.53 mm ID 10 m film CP-
31、LowoxThe two columns are coupled through a four-port Valco valve asshown in Fig. 1When analyses are not being performed, the GC oven temperatureshould be kept at 250C, and the pre-column carrier headpressure kept at 60 psi. This procedure conditions the CP-Lowoxcolumn, which may trap carrier gas con
32、taminants at the normal40C starting temperature, and also elutes residual heavy materialfrom the pre-column.Carrier gas Pre-column: 10 psi (20 min) 99 psi/min to 60 psi (until end of oventemperature program)CP-Lowox column flow: constant flow of 10 mL/minValve temperature 260CValve timing 1. Valve o
33、n at 2.80 min and off at 4.00 min to transfer the methanolfrom the polydimethylsiloxane column to the CP-Lowox column2. Valve on at 6.80 min and off at 8.00 min to transfer the internalstandard, 1-propanolD705904e12Fig. 7. The pre-column is located in a separate auxiliary oven.Fig. 8 gives a chromat
34、ogram obtained with this system.6.1.4 Configuration DDirect PTV (no splitting) injectionwith a single heartcut for the methanol and the 1-propanolinternal standard and several low boiling hydrocarbons, fol-lowed by backflush of the pre-column through the injector to avent by pressure switching. Tabl
35、e 4 and Figs. 9 and 10 giveflow configurations and operating conditions.6.1.5 Configuration ESplit injection using pressureswitching between the pre-column and the analytical column.After transfer to the analytical column, pressure is reduced atthe inlet and the pre-column is backflushed to remove h
36、ighboiling crude components. Table 5 and Fig. 11 give the flowconfigurations and operating conditions.6.2 DetectorAt least one, main flame ionization detector(FID) is required. In a two FID detector configuration, theoptional second detector is used to monitor the pre-columnelution and aids in setti
37、ng heartcut or transfer times for themethanol and 1-propanol. The main detectors response, pro-portional to the concentrations of the methanol and 1-propanol,is recorded; the peak areas are measured; and the concentrationof methanol is calculated with reference to the 1-propanolinternal standard and
38、 a calibration curve.6.3 Valve or Pneumatic (pressure) Switching, for systemsusing valve switching (for example, Configurations A, B in6.1), a high temperature and low volume valve, located withinthe gas chromatographic column oven or in a separate oven,capable of performing the functions described
39、in 6.1. The valveconnections shall not contribute significantly to chromato-graphic deterioration. Refer to Fig. 2, Fig. 3, and Fig. 8 forcompound peak performance, manufacturers guidelines andexamples given in 6.1 as a guide in assembling the GC system.For example, Valco Model No. A 4C10WP, 1.6-mm
40、(116-in.)fittings was used in Configuration A (6.1). Other equivalentvalves may be used. Alternatively, pneumatic or pressureFIG. 1 Valve Diagram for Configuration ANOTETwo separate injections: TOP/ methanol/1-propanol internal standard solution and BOTTOM/crude oil only.FIG. 2 Relative Retention Wi
41、ndows on Polydimethylsiloxane Pre-column in Configuration A Using Monitor FIDD705904e13switching may be used instead of a valve (for example,Configurations C, D, and E in 6.1).6.3.1 When using valve switching for heart-cutting, anautomatic valve-switching device must be used to ensurerepeatable swit
42、ching times. Such a device must be synchro-nized with injection and data collection times. For the pressureswitching (Configurations C, D, and E) approach, automaticprecise and stable pressure control must be used to yield stableretention times.6.4 Injection SystemSeveral sample injection systemshav
43、e been used successfully with the configurations in 6.1.Generally, splitless or direct injection types allow detection oflower levels (1 ppm or less) of methanol. The splitless or directinjection systems include: (A) a cool-on-column temperatureprogrammable vaporizer, and appropriate autosampler to
44、allowsuch injections (Configuration A in 6.1); and (B) PTV (Con-figuration D in 6.1). Alternatively, heated, splitting type injec-tors may be used with low split ratios (Configurations B, C, andEin6.1). The splitting type of injection generally is applicablefor concentrations greater than or equal t
45、o 2 ppm methanol.With splitting type injectors, the replaceable glass deactivatedliner (single-taper style with deactivated glass wool at thebottom to retain unvaporized components) was used success-fully (for example, as in Configuration C in 6.1).6.4.1 Automatic microlitre syringe injectors must b
46、e usedfor introducing representative samples into the GC inlet.FIG. 3 Chromatogram of Methanol and 1-propanol Internal Standard with Configuration AFIG. 4 Chromatogram of 5 ppm Methanol with Configuration AD705904e14Cool-on-column automated injectors may need special syringeneedles, and so forth. Fo
47、llow the manufacturers instructions.6.5 Data Presentation or Calculation:6.5.1 RecorderA data system is used for recording andevaluating the chromatograms.6.5.2 Integrator or ComputerA computer or electronicintegrator is used to obtain peak areas.6.6 Pre-column WCOT, containinga5mfilmthickness ofcro
48、ss-linked polymethyldisiloxane, or equivalent, to meet all ofthe requirements in this test method. This column performs apre-separation of the methanol and 1-propanol internal stan-dard from hydrocarbons in the same boiling point range. Thecolumn shall perform at the same temperature as required for
49、the column in 6.6.2, except if located in a separate auxiliaryoven. The configurations in 6.1 give examples of columns usedsuccessfully.6.7 Analytical Column, WCOT CP-Lowox column, 10-mlong by 0.53-mm inside diameter fused silica WCOT columnwith a 10 m film thickness. This column was used in thecooperative study to provide the precision data referred to inSection 14. An equivalent column with a retention index formethanol 1400 at 150C isothermally and which meets allother method specifications may be used. Ensure that acetonedoes not inte
