1、Designation: D7059 09Standard Test Method forDetermination of Methanol in Crude Oils byMultidimensional Gas Chromatography1This standard is issued under the fixed designation D7059; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t
2、he 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*1.1 This test method covers the determination of methanolin crude oils by direct injection multidimensional ga
3、s 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 equal to 0.1 % (v/v) water.1.3 This test method has not been tested with crude oilsamples that
4、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 of this test method.1.5 This standard does not purport to address all of thesafety concerns,
5、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:2D4006 Test Method for Water in Crude Oil by D
6、istillationD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD4928 Test Methods for Water in Crude Oils by Coulom-etric Karl Fischer TitrationD6596 Practice for Ampulization and Storage of Gasolineand Re
7、lated Hydrocarbon Materials3. Terminology3.1 Definitions:3.1.1 analytical column, nporous layer open tubular(PLOT) column with a stationary phase selective for oxygen-ates. It is used to resolve methanol from 1-propanol to provideaccurate quantitative results.3.1.2 cool-on-column injector, nan injec
8、tion 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 portconnected to the column.3.1.2.1 DiscussionAfter the injection, the injection port isheated at a fixed
9、 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.3.1.3 electronic pressure control, nelectronic pneumaticcontrol of carrier gas flows. It can be flow or pre
10、ssureprogrammed 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 zero dead-volume union.3.1.5 pre-column, na polydimethylsiloxane WCOT col-umn used to isolate the methano
11、l 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 programmable temperature vaporizer (PTV), natemperature programmable injector similar to a cool-on-column injecto
12、r 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 DiscussionThe liner may be replaced, as neces-sary, to remove non-volatile materials. This injector may
13、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 ofthe injected sample into two unequal portions, the smaller ofwhich goes to the capillary column, and the greater to a v
14、ent.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.04.0L on Gas Chromatography Methods.Current edition approved Oct. 1, 2009. Published November 2009.Originallyapproved in 2004. Last previous e
15、dition approved in 2004 as D7059-041. DOI:10.1520/D7059-09.2For 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.1*
16、A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.7.1 DiscussionWhen the vent is closed, the entiresample enters the capillary column and the inlet is operated asa spl
17、itless injector. When the vent is 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, th
18、eratio of the total flow of carrier 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,
19、is added to the sample,which is then 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 unwa
20、nted hydrocar-bons. The methanol and 1-propanol are transferred to theanalytical PLOT column for oxygenates. While the methanoland 1-propanol are eluting from the analytical PLOT columnfor oxygenates, auxiliary carrier gas is used to elute higherboiling crude oil hydrocarbons from the pre-column, ei
21、ther inthe forward or backflush mode, to yield a stable baseline for thenext 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. Appar
22、atus6.1 ChromatographA multidimensional two-WCOT col-umn 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 column
23、s may be accomplished by either using a valveor pneumatic (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 contro
24、l for the typical pressures required.Such flow controllers 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 require
25、ments of this test method.6.1.1 Configuration ACool-on-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. Fi
26、gs. 2-5 give chromatogramsand a calibration curve.6.1.2 Configuration BHeated split injection with a singleheartcut of methanol, 1-propanol and several C9minus hydro-carbons transferred to the PLOT column for oxygenates usinga six-port valve. The pre-column, located in a separate auxil-iary oven, is
27、 backflushed to a vent using the six-port valve.Table 2 and Fig. 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 t
28、he high boiling hydrocarbons retainedon the pre-column. The chromatographic 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
29、 microlitre injected withautosamplerOven temperature program 40C 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 po
30、lydimethylsiloxane (pre-column)10 m 3 0.53 mm ID 10 m film CP-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
31、 conditions the CP-Lowoxcolumn, which may trap carrier gas contaminants 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
32、flow of 10 mL/minValve temperature 260CValve timing 1. Valve on 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-propanolD7059 092Fig. 7. The pre-column i
33、s located in a separate auxiliary oven.Fig. 8 gives a chromatogram 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-col
34、umn through the injector to avent by pressure switching. Table 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 redu
35、ced atthe inlet and the pre-column is backflushed to remove highboiling 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 detect
36、or is used to monitor the pre-columnelution and aids in setting 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 cal
37、culated with reference to the 1-propanolinternal standard and 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
38、 separate oven,capable of performing the functions described 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
39、 the GC system.For example, Valco Model No. A 4C10WP, 1.6-mm (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 so
40、lution and BOTTOM/crude oil only.FIG. 2 Relative Retention Windows on Polydimethylsiloxane Pre-column in Configuration A Using Monitor FIDD7059 093switching 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
41、valve-switching device must be used to ensurerepeatable switching 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 t
42、imes.6.4 Injection SystemSeveral sample injection systemshave 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 temper
43、atureprogrammable vaporizer, and appropriate autosampler to 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 gener
44、ally is applicablefor concentrations greater than or equal to 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
45、 in 6.1).6.4.1 Automatic microlitre syringe injectors must be 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 AD7059 094Cool-on-column automated
46、injectors may need special syringeneedles, and so forth. Follow 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
47、areas.6.6 Pre-column WCOT, containinga5mfilmthickness ofcross-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. Thec
48、olumn shall perform at the same temperature as required forthe column in 6.7, except if located in a separate auxiliaryoven. The configurations in 6.1 give examples of columns usedsuccessfully.6.7 Analytical Column, a PLOT column for oxygenates, 10m long by 0.53 mm I.D., with a stationary phase coat
49、ed onto afused silica capillary or equivalent. At a minimum, the columnshall have sufficient retention for methanol that it elutes aftern-tridecane (retention index 1300) at 150C, and have suffi-cient efficiency and capacity to resolve methanol from1-propanol to provide accurate quantitative results. Ensure thatacetone does not interfere with the methanol analysis byanalyzing a 1000 ppm mixture of acetone in crude oil contain-ing the 1-propanol internal standard after the system has beenoptimized.7. Reagents and Materials7.1 Carrier Ga
