1、Designation: D7573 18a1Standard 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.1NOTEThe research report footnote to Section 15 was editorially updated in January 2019.1.
3、Scope1.1 This test method covers the determination of totalcarbon (TC), inorganic carbon (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/
4、L. Concentrations of 504000 mg/L of carbonmay be determined by automated injection of less 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
5、 forced through alayer of catalyst ensuring conversion of all carbon containingcompounds 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 the
6、n acidified and purged to remove the IC.The purged inorganic carbon is measured as TIC, or 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
7、 injected todetermine NPOC.1.5 This test method is applicable to the matrices andconcentrations 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 a
8、pplicable only to carbonaceousmatter in the sample that can be introduced into the reactionzone. 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 monito
9、ring.1.8 The values stated in SI units are to be regarded asstandard. No other units of measurement 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
10、 appro-priate safety, health, and environmental practices and deter-mine the applicability 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
11、 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 WaterD1192 Guide for Equipment for Sampling Water and Steamin Closed Cond
12、uits (Withdrawn 2003)3D1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Flowing ProcessStreamsD4448 Guide for Sampling Ground-Water Monitoring WellsD5847 Practice for
13、Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisD6538 Guide for Sampling Wastewater With AutomaticSamplers1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.06 on Methods forAnalysis forOrga
14、nic Substances in Water.Current edition approved Dec. 15, 2018. Published January 2019. Originallyapproved in 2009. Last previous edition approved in 2018 as D7573 18. DOI:10.1520/D7573-18AE01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at se
15、rviceastm.org. For Annual 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,
16、 PA 19428-2959. United StatesThis 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 Organizatio
17、n Technical Barriers to Trade (TBT) Committee.1D6759 Practice for Sampling Liquids Using Grab and Dis-crete Depth Samplers3. 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 o
18、rganic carbon (DOC), ncarbon deter-mined on filtered samples.3.2.2 inorganic carbon (IC), ncarbon in 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 pur
19、gable organic carbon (POC), ncarbon thatpurges from acidified samples, also known as volatile organiccompounds (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),
20、ncarbon in the form oforganic compounds.4. Summary of Test Method4.1 FundamentalsCarbon can occur in 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 isdetermine
21、d on samples that have been filtered through a0.45-m filter.4.2 TOC and DOC procedures require that 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 dete
22、ctor. Failure of the method to remove all IC prior toanalysis for organic carbon will result in significant 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
23、, andindustrial sources. In its most common form, this test methodis used to measure organic carbon 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-
24、eters such as chemical oxygen demand (COD) and total oxygendemand (TOD) is described in the literature.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
25、resultingcarbon dioxide is measured by a non-dispersive infrareddetector (NDIR). Suspended and refractory 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
26、.6.3 Homogenizing or sparging of a sample, or both, maycause loss of purgable organic compounds, thus 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. Com
27、parison of the difference, if any, betweenNPOC and TOC by subtraction represents POC lost duringsparging.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 fr
28、om twolarge levels. For example, a ground water high in IC and lowin TOC will give a poorer TOC value 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 g
29、enerally found in water samples. Elementalcarbon does not form during the catalytic oxidation of watersamples.6.8 Inorganics dissolved in the sample are not volatilizedinto gas and remain on the catalyst or quartz shard surfaces.4Handbook for Monitoring Industrial Wastewater, Section 5.3, U.S. Envir
30、on-ment Protection Agency, August 1973, pp. 512.FIG. 1 TIC RemovalD7573 18a12High amounts of solids eventually react with the quartzsurfaces causing devitrification, or solidify in the catalyst beddecreasing flow rates. Limit sample volume injected to reducethe amount of soluble salts and to reduce
31、cooling of thereaction chamber. Buildup of salts; reduction of flow rate, orlarge injection volumes 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.
32、0mg/L) bears special consideration requiring that the same waterused to set the baseline be used to 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 caus
33、e consid-erable inaccuracies in low-level TIC analysis. For instance, a40-millilitre vial of reagent 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 orga
34、nic carbon content with time.The small levels of organics absorbed into reagent water cancause considerable 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
35、wool, quarts shards, orother items to protect the catalyst from dissolved salts to extendits life.7.2.2 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 scru
36、bber.7.2.3 DetectorThe CO2in the gas stream is detected by aCO2-specific NDIR detector.7.2.4 Detector 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
37、furnace cooling or variablecombustion rates of different organic molecules contained in asample.7.2.5 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 re
38、quires the use of sample bottles and vials certified aslow TOC. This avoids variable contribution of 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 inten
39、ded thatall reagents conform to the specifications of the Committee onAnalytical Reagents of theAmerican 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
40、 accuracy of thedetermination.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall 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 recommen
41、ded that NPOC be 0.05mg/L. Higher levels can affect the results of this test method,especially at progressively 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
42、 2, then sparging withfritted-glass sparger using CO2-free gas (time will depend onvolume and gas flow 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 solutio
43、ns. CO2-free water should beprotected from atmospheric contamination. Glass containersare required for 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 preservatio
44、n and TICremoval. Follow the manufacturers suggestions for acid andacid concentration used for TIC removal. 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 1
45、20C and quantitatively transfer to a 1000-millilitrevolumetric flask containing about 500 millilitres 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 forstor
46、age. This stock solution, or dilutions of it, is used tocalibrate and test performance of the carbon 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 abou
47、t 500 millilitres of reagent water. Stir todissolve and add 1 millilitre of concentrated hydrochloric 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 te
48、st performance of the carbon analyzer.8.6 Inorganic Carbon, Stock Calibration Standard Solution(1000 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 wate
49、r. Mix to dissolve, dilute to themark, and mix.8.7 Inorganic Carbon, IC Test Solution (Alkalinity 834 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 calibrat
