ASTM D7573-2018a Standard Test Method for Total Carbon and Organic Carbon in Water by High Temperature Catalytic Combustion and Infrared Detection.pdf

1、Designation: D7573 18aStandard Test Method forTotal Carbon and Organic Carbon in Water by HighTemperature Catalytic Combustion and Infrared Detection1This standard is issued under the fixed designation D7573; the number immediately following the designation indicates the year oforiginal adoption or,

2、 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 totalcarbon (TC), inorganic carbon

3、(IC), total organic carbon(TOC), dissolved organic carbon (DOC), and non-purgableorganic carbon (NPOC) in drinking water, groundwater, sur-face water, wastewater, and seawater in the range from 0.5mg/L to 50 mg/L. Concentrations of 504000 mg/L of carbonmay be determined by automated injection of les

4、s samplevolume or by sample dilution. Alternatively, use less samplevolume and calibrate at higher concentrations1.2 The sample is injected into a tube heated at 680C. Thesample converts into a gaseous phase and forced through alayer of catalyst ensuring conversion of all carbon containingcompounds

5、to CO2. A non-dispersive infrared (NDIR) detectormeasures the resulting CO2.1.3 For TOC and DOC analysis a portion of the sample isinjected to determine TC or dissolved carbon (DC). A portionof the sample is then acidified and purged to remove the IC.The purged inorganic carbon is measured as TIC, o

6、r DIC. TOCor DOC is calculated by subtracting the inorganic fraction fromthe total carbon:TOC 5 TC 2 IC (1)1.4 For NPOC analysis a portion of sample is acidified andpurged to remove IC. The purged sample is then injected todetermine NPOC.1.5 This test method is applicable to the matrices andconcentr

7、ations validated in the inter-laboratory study. It is theusers responsibility to ensure the validity of this test methodfor waters of untested matrices and different concentrationranges.1.6 This test method is applicable only to carbonaceousmatter in the sample that can be introduced into the reacti

8、onzone. The syringe needle or injector opening size generallylimits the maximum size of particles that can be so introduced.1.7 In addition to laboratory analyses, this test method maybe applied to stream monitoring.1.8 The values stated in SI units are to be regarded asstandard. No other units of m

9、easurement are included in thisstandard.1.9 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, health, and environmental practices and deter-mine the applicabilit

10、y of regulatory limitations prior to use.1.10 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the Wor

11、ld Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1192 Guide for Equipment for Sampling Water and Steamin Closed Conduits (Withdrawn 2003)3D1193 Specification for Reagent WaterD2777 Practice for Determinati

12、on of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD4448 Guide for Sampling Ground-Water Monitoring WellsD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisD6538 Guide fo

13、r Sampling Wastewater With AutomaticSamplersD6759 Practice for Sampling Liquids Using Grab and Dis-crete Depth Samplers1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.06 on Methods forAnalysis forOrganic Substances in Wat

14、er.Current edition approved Dec. 15, 2018. Published January 2019. Originallyapproved in 2009. Last previous edition approved in 2018 as D7573 18. DOI:10.1520/D7573-18A.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annua

15、l Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United S

16、tatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to

17、Trade (TBT) Committee.13. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this standard, refer toTerminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 dissolved organic carbon (DOC), ncarbon deter-mined on filtered samples.3.2.2 inorganic carbon (IC), ncarbon i

18、n the form ofcarbon dioxide, carbonate ion, or bicarbonate ion.3.2.3 non-purgable organic carbon (NPOC), ncarbonmeasured in a sample after acidification and sparging toremove inorganic carbon.3.2.4 purgable organic carbon (POC), ncarbon thatpurges from acidified samples, also known as volatile organ

19、iccompounds (VOC).3.2.5 refractory material, nthat which cannot be oxidizedcompletely under the test method conditions.3.2.6 total carbon (TC), nthe sum of IC and TOC.3.2.7 total organic carbon (TOC), ncarbon in the form oforganic compounds.4. Summary of Test Method4.1 FundamentalsCarbon can occur i

20、n water as an inor-ganic and organic compound. This test method can be used tomake independent measurements of IC, NPOC, and TC, andcan also determine OC by the difference of TC and IC. DOC isdetermined on samples that have been filtered through a0.45-m filter.4.2 TOC and DOC procedures require that

21、 IC has beenremoved from the sample before it is analyzed for organiccarbon content. The sample free of IC is injected into the TOCinstrument where all carbon is converted to CO2and measuredby the detector. Failure of the method to remove all IC prior toanalysis for organic carbon will result in sig

22、nificant error. Adiagram of suitable apparatus is given in Fig. 1.5. Significance and Use5.1 This test method is used for determination of the carboncontent of water from a variety of natural, domestic, andindustrial sources. In its most common form, this test methodis used to measure organic carbon

23、 as a means of monitoringorganic pollutants in industrial wastewater. These measure-ments are also used in monitoring waste treatment processes.5.2 The relationship of TOC to other water quality param-eters such as chemical oxygen demand (COD) and total oxygendemand (TOD) is described in the literat

24、ure.46. Interferences and Limitations6.1 The oxidation of dissolved carbon to CO2is broughtabout at high temperatures (680C) in the presence of oxygen.A catalyst promotes the oxidation process and the resultingcarbon dioxide is measured by a non-dispersive infrareddetector (NDIR). Suspended and refr

25、actory materials are com-pletely oxidized under these conditions.6.2 Acid preservation can precipitate some compounds,such as humic acids, removing them from solution and causingerroneously low results.6.3 Homogenizing or sparging of a sample, or both, maycause loss of purgable organic compounds, th

26、us yielding avalue lower than the true TOC level. (For this reason, suchmeasurements are sometimes known as NPOC). The extentand significance of such losses must be evaluated on anindividual basis. Comparison of the difference, if any, betweenNPOC and TOC by subtraction represents POC lost duringspa

27、rging.6.4 If POC is important then TOC must be measured bysubtraction:TOC 5 TC 2 TIC (2)6.5 Note that error will be introduced when the method ofdifference is used to derive a relatively small level from twolarge levels. For example, a ground water high in IC and lowin TOC will give a poorer TOC val

28、ue as (TC IC) than bydirect measurement as NPOC.6.6 Samples containing high levels (1 ppm) of surfactantmay lose TOC by foaming.6.7 Elemental carbon may not be completely combusted;however, it is not generally found in water samples. Elementalcarbon does not form during the catalytic oxidation of wa

29、tersamples.6.8 Inorganics dissolved in the sample are not volatilizedinto gas and remain on the catalyst or quartz shard surfaces.High amounts of solids eventually react with the quartzsurfaces causing devitrification, or solidify in the catalyst bed4Handbook for Monitoring Industrial Wastewater, Se

30、ction 5.3, U.S. Environ-ment Protection Agency, August 1973, pp. 512.FIG. 1 TIC RemovalD7573 18a2decreasing flow rates. Limit sample volume injected to reducethe amount of soluble salts and to reduce cooling of thereaction chamber. Buildup of salts; reduction of flow rate, orlarge injection volumes

31、could result in peak splitting.6.9 Carbon in reagent water and reagent blanks can bereduced to a minimum, and consistent value, but cannot becompletely eliminated.Analyzing low-level TOC (less than 1.0mg/L) bears special consideration requiring that the same waterused to set the baseline be used to

32、prepare the calibrationstandards.6.10 Atmospheric carbon dioxide absorbs into reagent waterincreasing its inorganic carbon content with time. The smalllevels of CO2absorbed into reagent water can cause consid-erable inaccuracies in low-level TIC analysis. For instance, a40-millilitre vial of reagent

33、 water containing no detectable TICwas analyzed to contain 160 g/LTIC after 1 hour of exposureto ambient air.6.11 Trace organics in the atmosphere can be absorbed intoreagent water increasing its organic carbon content with time.The small levels of organics absorbed into reagent water cancause consi

34、derable inaccuracies in low-level (5 % of the NPOC. Fig.1 illustrates three different options for TIC removal.7.2.1.2 Combustion ChamberA heated catalyst containedin a quartz tube, may contain quartz wool, quarts shards, orother items to protect the catalyst from dissolved salts to extendits life.7.

35、2.2 Gas ConditioningThe gas passing from the reactoris dried, and the CO2produced is either trapped and laterreleased to the detector, or routed directly to the detectorthrough a halogen-removing scrubber.7.2.3 DetectorThe CO2in the gas stream is detected by aCO2-specific NDIR detector.7.2.4 Detecto

36、r ResponseIntegrated area unless CO2iscollected and desorbed from a CO2specific trap. Area integra-tion accurately quantifies carbon content in the event of split oroverlapping peaks that result from furnace cooling or variablecombustion rates of different organic molecules contained in asample.7.2.

37、5 Presentation of ResultsThe NDIR detector output isrelated to stored calibration data and then displayed as milli-grams of carbon per litre.7.3 Low TOC Sample ContainersAnalysis of TOC below10 ppm requires the use of sample bottles and vials certified aslow TOC. This avoids variable contribution of

38、 TOC and isespecially important when analyzing TOC below 1 ppm.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of theAmer

39、ican Chemical Society,5wheresuch specifications are available. Other grades may be used,provided it is first ascertained that the reagent is of sufficientpurity to permit its use without lessening the accuracy of thedetermination.8.2 Purity of WaterUnless otherwise indicated, referencesto water shal

40、l be understood to mean reagent water conformingto Specification D1193, Type I or Type II. The indicatedspecification does not actually specify inorganic carbon ororganic carbon levels but is recommended that NPOC be 0.05mg/L. Higher levels can affect the results of this test method,especially at pr

41、ogressively lower levels of the carbon content inthe samples to be measured. Where inorganic carbon in reagentwater is significant, CO2-free water may be prepared fromreagent water by acidifying to pH 2, then sparging withfritted-glass sparger using CO2-free gas (time will depend onvolume and gas fl

42、ow rate, and should be determined by test).Alternatively, if the carbon contribution of the reagent water isknown accurately, its effect may be allowed for in preparationof standards and other solutions. CO2-free water should beprotected from atmospheric contamination. Glass containersare required f

43、or storage of water and standard solutions. It isrecommended that the same reagent water be used in prepara-tion of all standards and blanks per calibration.8.3 AcidAcid is used for sample preservation and TICremoval. Follow the manufacturers suggestions for acid andacid concentration used for TIC r

44、emoval. Do not use nitricacid.8.4 Organic Carbon, Stock Calibration Standard Solution(1000 mg/L)Weigh 2.128 grams of anhydrous potassiumhydrogen phthalate (KHC8H4O4) previously dried for twohours at 120C and quantitatively transfer to a 1000-millilitrevolumetric flask containing about 500 millilitre

45、s of reagentwater. Stir to dissolve and add 1 millilitre of concentratedhydrochloric acid (HCl), dilute to the mark with reagent waterand mix. Transfer to an amber glass reagent bottle and cap forstorage. This stock solution, or dilutions of it, is used tocalibrate and test performance of the carbon

46、 analyzer.8.5 Organic Carbon, Stock Calibration Verification Solution(1000 mg/L)Weigh 2.377 grams of sucrose (C12H22O11) andquantitatively transfer to a 1000-millilitre volumetric flaskcontaining about 500 millilitres of reagent water. Stir todissolve and add 1 millilitre of concentrated hydrochlori

47、c acid(HCl), dilute to the mark with reagent water and mix. Transferto an amber glass reagent bottle and cap for storage. Thissolution, or dilutions of it, is used to verify calibration accuracyand test performance of the carbon analyzer.8.6 Inorganic Carbon, Stock Calibration Standard Solution(1000

48、 mg/L)Weigh 8.826 grams of anhydrous sodium car-bonate (Na2CO3) previously dried at 120C for two hours andtransfer to a 1000-millilitre volumetric flask containing about500 millilitres of reagent water. Mix to dissolve, dilute to themark, and mix.8.7 Inorganic Carbon, IC Test Solution (Alkalinity 83

49、4 mgCaCO3/L)Dilute 10 millilitres of the inorganic carbon stocksolution (Section 8.6) to 100 millilitres with reagent water. Usethis solution to verify IC removal.8.8 Calibration SolutionsTC, IC8.8.1 Organic Carbon Calibration SolutionsAt least 4calibration concentrations and a calibration blank (CB) areused to prepare an initial calibration curve. Standards areprepared to cover the concentration of interest from the organiccarbon stock calibration solution. Calibration standards areprepared in reagent water and preserved to pH 2 withconcentrated