1、Designation: D8028 17Standard Test Method forMeasurement of Dissolved Gases Methane, Ethane,Ethylene, and Propane by Static Headspace Sampling andFlame Ionization Detection (GC/FID)1This standard is issued under the fixed designation D8028; the number immediately following the designation indicates
2、the year oforiginal adoption or, in the 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 determination of the
3、 dis-solved gases methane, ethane, ethylene, and propane indrinking, waste, and ground waters, including domestic wellswhether naturally occurring or resulting from commercialactivities, or both. This test method has an analytical rangefrom 10 g/L to 11 000 g/L for methane, and 10 g/L to 5000g/L for
4、 ethane, ethylene, and propane. If a sample has adissolved gas concentration above the calibration range, thesample would require dilution. Other analytical ranges may beused as long as the instrument calibration encompasses thedesired range and demonstrates adequate linearity.1.2 This test method i
5、s applicable to samples collected at anominal ambient pressure. Samples collected under highpressures, that is, above ambient pressure, may not be accu-rately analyzed using this method.1.3 This test method is applicable to a variety of dissolvedgases; however, for the present standard, only methane
6、, ethane,ethylene, and propane were validated. In order to validate fora gas not listed in this method, the analyst would need toestablish the saturation concentration of the new gas, andestablish a valid curve, method detection limits, and demon-stration of capability following the procedures outli
7、ned in thismethod.1.4 It is the analysts responsibility to ensure the validity ofthis test method for dissolved gases other than methane, ethane,ethylene, and propane and other sample matrices.1.5 UnitsThe values stated in SI units are to be regardedas the standard. No other units of measurement are
8、 included inthis standard.1.6 A single laboratory study was done in order to establishprecision and bias for the surrogate (see Section 16).1.7 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 t
9、o establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.8 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Prin
10、ciples for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD8006 Guide for Sampl
11、ing and Analysis of Residential andCommercial Water Supply Wells in Areas of Explorationand Production (Ewhether naturally occurring or resulting from commercialactivities, dissolved gases can be hazardous both to theenvironment and humans. Due to increased scrutiny of dis-solved gases, developing a
12、 valid method for the testing ofdissolved gases in water has become more imperative. Staticheadspace sampling is generally applicable for sampling thesecompounds. However, as these compounds are extremelyvolatile, a closed sampling system is recommended. This testmethod can be used for quantitativel
13、y determining dissolvedgases in ground, waste, and drinking waters.5.2 This test method is suitable for analysis of domesticdrinking water samples from residential and commercial watersupply wells prior to oil and gas exploration activities to forma baseline for monitoring potential impacts during e
14、xploration;development, including hydraulic fracturing; operation; clo-sure; and reclamation of nearby oil and gas production andinjection wells.6. Interferences6.1 Impurities in the air, the field sample vials, vial septa,the preservatives, or improper sealing during transport cancause contaminatio
15、n. Field reagent blanks, recommended, andmethod blanks, required, shall be used to verify propersampling and handling procedures.6.2 Contamination or carryover can occur whenever ahighly concentrated sample is run. A blank shall be run after ahighly concentrated sample to ensure system cleanliness.6
16、.2.1 A carryover study should be done in order to deter-mine the nominal level of analytes that will be prone to carryover into subsequent samples. From this study, the laboratoryshall be required to run blanks after samples containinganalytes above the established levels. Otherwise, if a sample isr
17、un directly after a high level sample, reference the laboratorycarryover study, and displays an analyte of interest, the samplewould need to be run again in order to ensure the accuracy ofthe results.6.3 The FID is a nonselective detector. If matrix interferencecaused by sample contamination or comp
18、ound co-elutionoccurs, an experienced analyst is required for proper interpre-tation.6.4 In order to inhibit analyte loss, samples should be storedin 40-ml vials with polytetrafluoroethylene (PTFE)-lined chlo-robutyl septa with no headspace, and placed on ice within 15minutes of collection. Samples
19、should be transported and keptcooled to approximately 0 to 6C but not frozen. If any visibleheadspace exists in a sample vial, it is to be noted in the resultsreport as analyte loss can exist with sample headspace.Samples may be preserved with sulfuric acid in order to extendthe expiration date to t
20、wo weeks from the sampling date.7. Apparatus7.1 Sample containers, 40-ml screw top vials sealed withPTFE-lined chlorobutyl septa.7.2 Water bath, capable of maintaining water temperature at20C (60.5C) to prepare calibration and laboratory controlstandards. Temperatures other than 20C may be used, as
21、longas the saturated solution concentration at the temperature isknown.7.3 Digital thermometer.7.4 Gastight syringes, 10 l to 2.5 ml.7.5 Two gastight syringes fitted with removable needles andLuer lock valves, 25 ml.7.6 Glass-stoppered class A volumetric flasks, 5 to 100 ml.7.7 Stir bars, (required
22、only for sample agitation throughstirring) magnetic stir bars sized to fit in the 40-ml screw-topvials.7.8 Ultra high purity (UHP) inert gas, used to purge theinstrument headspace vial to displace any contaminants in thevial. Acceptable gases are helium and nitrogen.7.9 Sample Transfer DeviceA trans
23、fer device capable oftransferring sample or standard from the sample 40-ml vial toa separate 40-ml vial purged with an inert gas such as nitrogenor helium (recommended) and incorporated with a stir bar andsurrogate standard. (A stir bar is not needed if sample agitationis done by means other than st
24、irring such as vial shaking.) It isrecommended that sample transfer is done with a sealeddevice/system. See Fig. 1.NOTE 1The removable needle needs to be fitted with a Luer lockvalve to ensure the sample is not exposed to atmosphere during the sampletransfer. See Fig. 1.7.10 Sample AgitationSamples
25、can be agitated to achieveequilibrium of the dissolved gases in the headspace rapidly.D8028 173The sample agitation procedure is discretionary; however, itshall be established that equilibrium of the sample system isachieved with or without an agitation procedure and sampleagitation shall be done wi
26、thout exposing the sample to theatmosphere. Furthermore, all sample, standard, spike, andblank agitation shall be done in the exact same manner.7.11 Headspace Sampling SystemAn automated samplingsystem capable of performing static headspace can be used asthe sample introduction system to the GC. The
27、 system must beable to inject the volume necessary to meet the detection limitsset forth in this test method. An automated sampling systemmay be used for the sample transfer, agitation, and headspacesampling as long as it meets all of the manual sample transfercriteria stated above.77.12 Gas chromat
28、ograph (GC), capable of temperature andpressure programming with a split/splitless injection port.7.13 Flame Ionization Detector (FID)Follow the instru-ment manufacturers recommendations for gases, flow rates,and operation.7.14 Capillary or Packed Gas Chromatograph (GC)ColumnAny column that meets th
29、e performance specifica-tions of this test method. Sample components are identified bytheir relative retention time. Because of possible sample matrixinterferences, co-elution, and elevated contamination fromother compounds, the sample chromatograms can be difficult toanalyze. At least a 50 % resolu
30、tion of the height of the valleybetween any contaminants and the analyte of interest isrequired and a retention time window of no greater than 5 %from the daily continuing calibration check is required foridentification. Examples of columns found suitable:7.14.1 Column 1, 30-m by 0.53-mm inside diam
31、eter (ID) by20-m, nonpolar porous layer open tubular (PLOT) columnincorporating 100 % divinylbenzene.87.14.2 Column 2, 2-m by 1.0-mm ID by 1.6-mm outsidediameter (OD) silco, packed column, shin carbon ST 100/120.97The EST Analytical LGX50 Autosampler was used for the laboratory studies.Autosamplers
32、from other vendors that are able to generate similar methodperformance and that achieve adequate sampling may be used.8A RESTEK QS-BOND PLOT Column (Cat# 19738) was used to develop thistest method and generate the precision and bias data presented in Section 16.RESTEK Corporation, Bellefonte, PA 168
33、23. Columns from other vendors that areable to generate similar method performance and that achieve adequate resolutionmay be used.9RESTEK Shin Carbon ST Column (Cat #19808) was used to develop this testmethod. RESTEK Corporation, Bellefonte, PA 16823. Columns from other vendorsthat are able to gene
34、rate similar method performance and that achieve adequateresolution may be used.FIG. 1 Sample Transfer GraphicD8028 1748. Reagents and Materials8.1 Purity of ReagentsReagent-grade chemicals shall beused in all tests. It is intended that all reagents conform to thespecifications of the Committee on A
35、nalytical Reagents of theAmerican Chemical Society where such specifications areavailable.10Other grades may be used, provided it is firstascertained that the reagent is of sufficiently high purity topermit its use without lessening the accuracy of the determi-nation.8.2 Compressed Gases:8.2.1 Heliu
36、m or HydrogenUHP grade or equivalent, forGC system carrier gas.8.2.2 AirZero grade or equivalent, for use as FID fuel gas.8.2.3 HydrogenUHP grade or equivalent, for use as FIDfuel gas.8.2.4 NitrogenUHP grade or equivalent, for sweeping theinstrument sample vials.8.3 Waters and Solvents:8.3.1 Reagent
37、 Grade WaterUnless otherwise indicated,references to water shall be understood to mean reagent waterthat meets purity specifications of Specification D1193.8.3.2 MethanolHigh purity laboratory control matrixspike (LC-MS) grade or equivalent, for preparation of surro-gate working standard.8.4 Certifi
38、ed Gas CylindersPurity of 99 % for preparationof stock solutions. Certificate of analysis required.8.4.1 MethanePrimary and secondary source.8.4.2 EthanePrimary and secondary source.8.4.3 EthylenePrimary and secondary source.8.4.4 PropanePrimary and secondary source.8.5 Stock Standard SolutionPrepar
39、ation of the methane,ethane, ethylene, and propane stock standard solutions areprepared fresh and expire after two weeks if preserved, seeAppendix X1. The expiration date may be extended if alternatestorage conditions for laboratory prepared standards are dem-onstrated using the process described in
40、 Appendix X1.Ifacertified reference material (CRM) is procured with a certifi-cate of analysis (COA) denoting a different expiration periodspecified by the manufacturer, the expiration denoted on theCRM can be used.8.5.1 Set up a recirculating bath set to 20C 6 0.5C at 1atm pressure in a laboratory
41、fume hood.NOTE 2The saturation concentration of the solution varies with thetemperature of the water and atmospheric pressure; thus, the temperatureof the water shall be controlled. Alternative saturation temperatures areacceptable as long as the saturation concentrations are documented.8.5.2 The sa
42、turation concentrations at 20C and 1 atmpressure of the gases in this test method are as follows:11,128.5.2.1 Methane23.2 mg/L.8.5.2.2 Ethane62.0 mg/L.8.5.2.3 Ethylene149.0 mg/L.8.5.2.4 Propane76.7 mg/L.8.5.3 Fill a 500-ml volumetric flask to the neck with waterand place it in the recirculating bath
43、 ensuring that the reagentgrade water in the flask is submerged in the recirculating bath.Let the reagent grade water sit in the bath for long enough forthe water to reach 20C (60.5C) using a calibrated digitalthermometer.8.5.4 Connect a flexible piece of tubing to the certified gascylinder. Then, a
44、ttach a glass pipette or a frit to the other endof the tubing. Finally, place the pipette/frit at the end of thetubing into the reagent water in the submerged volumetricflask. Tubing should be polyether ether ketone (PEEK), PTFE,or clean copper.8.5.5 Open the valve of the certified gas cylinder enou
45、gh toensure vigorous bubbling of the gas in the water. Bubble thecertified gas in the water for at least 30 min to ensure completesaturation.NOTE 3200 to 250-ml/min gas flow into 500 ml of water for 30 minis sufficient to ensure saturation. Flow rate, time, and temperature needs tobe documented.8.5.
46、6 Repeat this procedure with a secondary source for thesecondary source stock standard solution.8.5.7 Alternative means of producing or procuring water-based standards of the dissolved gases of known concentrationare acceptable provided they meet all quality assurance criteriadescribed in this test
47、method. A CRM with a COA can also beused for the stock solution.8.6 Initial Calibration (ICAL) SolutionsPrepared from theprimary stock solution standard.8.6.1 ICAL solutions are prepared by performing serialdilutions on the primary stock standard solution into a volu-metric flask. The dilutions shal
48、l be performed while the stocksolution is still being purged with the analyte gas to ensure thesolution is consistently saturated. These dilutions need to beimmediately transferred to a 40-ml vial with PTFE-linedchlorobutyl septa with no headspace until transferred to theinstrument sample vial. Thes
49、e solutions shall be refrigeratedwhen not in use.8.6.2 Alternative means of producing or procuring water-based standards of the dissolved gases of known concentrationare acceptable provided they meet all quality assurance criteriadescribed in this test method. A CRM with a COA can also beused to prepare ICAL solutions.NOTE 4The temperature of the standards during handling,preparation, and dilution is as important as the temperature during theequilibrium step. All steps for the solution preparation, sample transfer,and dilution steps need to b
