ASTM D5904-2002(2017) 9054 Standard Test Method for Total Carbon Inorganic Carbon and Organic Carbon in Water by Ultraviolet Persulfate Oxidation and Membrane Conductivity Detectio.pdf

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1、Designation: D5904 02 (Reapproved 2017)Standard Test Method forTotal Carbon, Inorganic Carbon, and Organic Carbon inWater by Ultraviolet, Persulfate Oxidation, and MembraneConductivity Detection1This standard is issued under the fixed designation D5904; the number immediately following the designati

2、on indicates 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 determi

3、nation of totalcarbon (TC), inorganic carbon (IC), and total organic carbon(TOC) in water in the range from 0.5 to 30 mg/L of carbon.Higher levels may be determined by sample dilution. The testmethod utilizes ultraviolet-persulfate oxidation of organiccarbon, coupled with a CO2selective membrane to

4、recover theCO2into deionized water. The change in conductivity of thedeionized water is measured and related to carbon concentra-tion in the oxidized sample. Inorganic carbon is determined ina similar manner without the requirement for oxidation. In bothcases, the sample is acidified to facilitate C

5、O2recovery throughthe membrane. The relationship between the conductivitymeasurement and carbon concentration is described by a set ofchemometric equations for the chemical equilibrium of CO2,HCO3,H+, and the relationship between the ionic concentra-tions and the conductivity. The chemometric model

6、includesthe temperature dependence of the equilibrium constants andthe specific conductances.1.2 This test method has the advantage of a very highsensitivity detector that allows very low detection levels onrelatively small volumes of sample. Also, use of two measure-ment channels allows determinati

7、on of CO2in the sampleindependently of organic carbon. Isolation of the conductivitydetector from the sample by the CO2selective membraneresults in a very stable calibration, with minimal interferences.1.3 This test method was used successfully with reagentwater spiked with sodium bicarbonate and va

8、rious organicmaterials. It is the users responsibility to ensure the validity ofthis test method for waters of untested matrices.1.4 This test method is applicable only to carbonaceousmatter in the sample that can be introduced into the reactionzone. The injector opening size generally limits the ma

9、ximumsize of particles that can be introduced.1.5 In addition to laboratory analyses, this test method maybe applied to on line monitoring.1.6 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.7 This standard does not purport to

10、 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 use.2. Referenced Documents2.1 ASTM Standards:2D1129 Ter

11、minology Relating to WaterD1192 Guide for Equipment for Sampling Water and Steamin Closed Conduits (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 C

12、losed ConduitsD5810 Guide for Spiking into Aqueous SamplesD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water Analysis3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this standard, refer toTerminology D1129.3.2 Definitions of Terms Specif

13、ic to This Standard:3.2.1 inorganic carbon (IC), ncarbon in the form ofcarbon dioxide, carbonate ion, or bicarbonate ion.3.2.2 potassium hydrogen phthalate (KHP), nKHC8H4O4.3.2.3 refractory material, nthat which cannot be oxidizedcompletely under the test method conditions.1This test method is under

14、 the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.06 on Methods forAnalysis forOrganic Substances in Water.Current edition approved Feb. 1, 2017. Published February 2017. Originallyapproved in 1996. Last previous edition approved in 2007 as D5904 02

15、 (2007).DOI: 10.1520/D5904-02R17.2For 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.3The last approved version o

16、f this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established i

17、n the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.2.4 total carbon (TC), nthe sum of IC and TOC.3.2.5 total organic carbon (TOC), ncarbon in the form oforganic c

18、ompounds.4. Summary of Test Method4.1 FundamentalsCarbon can occur in water as inorganicand organic compounds. This test method can be used to makeindependent measurements of IC and TC and can also deter-mine TOC as the difference of TC and IC. If IC is high relativeto TOC it is desirable to use a v

19、acuum degassing unit to reducethe IC concentration as part of the measurement. Alternatively,the IC can be removed by acidifying and sparging the sampleprior to injection into the instrument.4.2 The basic steps of this test method are:4.2.1 Removal of IC, if desired, by vacuum degassing;4.2.2 Conver

20、sion of remaining inorganic carbon to CO2byaction of acid in both channels and oxidation of total carbon toCO2by action of acid-persulfate, aided by ultraviolet (UV)radiation in the TC channel;FIG. 1 Schematic Diagram of TOC Analyzer SystemD5904 02 (2017)24.2.3 Detection of CO2that is swept out of t

21、he reactors bythe liquid stream over membranes that allow the specificpassage of CO2to high purity water where change in conduc-tivity is measured; and4.2.4 Conversion of the conductivity detector signal to adisplay of carbon concentration in parts per million(ppm = mgL) or parts per billion (ppb =

22、gL). The IC chan-nel reading is subtracted from the TC channel to give a TOCreading. A diagram of suitable apparatus is given in Fig. 1.References (1-5)4provide additional information on this testmethod.5. Significance and Use5.1 This test method is used for determination of the carboncontent of wat

23、er from a variety of natural, domestic, andindustrial sources. In its most common form, this test methodis used to measure organic carbon as a means of monitoringorganic pollutants in high purity and drinking water. Thesemeasurements are also used in monitoring waste treatmentprocesses.5.2 The relat

24、ionship of TOC to other water quality param-eters such as chemical oxygen demand (COD) and total oxygendemand (TOD) is described in the literature (6).6. Interferences and Limitations6.1 The oxidation of dissolved carbon to CO2is broughtabout at relatively low temperatures by the chemical action ofr

25、eactive species produced by UV-irradiated persulfate ions. Notall suspended or refractory material may be oxidized underthese conditions; analysts should take steps to determine whatrecovery is being obtained. This may be done by severalmethods: by rerunning the sample under more vigorous reac-tion

26、conditions; by analyzing the sample by an alternativemethod known to result in full recovery; or by spiking sampleswith known refractories and determining recovery.6.2 Chloride ion above 250 mg/L tends to interfere withoxidative reaction mechanisms in this test method. Followmanufacturers instructio

27、ns for dealing with this problem.Other interferences have been investigated and found to beminimal under most conditions. Refer to the references formore information.6.3 Note that error will be introduced when the method ofdifference is used to derive a relatively small level from twolarge levels. F

28、or example, a ground water high in IC and lowin TOC will give a poorer TOC value as (TC-IC) than by directmeasurement. In this case the vacuum degassing unit on theinstrument should be used to reduce the concentration of ICprior to measurement. Alternatively, the sample can be acidi-fied and sparged

29、 prior to introduction into the instrument. Useof the vacuum degassing unit or sparging the sample may causeloss of volatile organic compounds, thus yielding a value lowerthan the true TOC level.6.4 Use of the vacuum degassing unit or sparging thesample may cause loss of volatile organic compounds,

30、thusyielding a value lower than the true TOC level. At low TOClevels, the degassing unit may introduce a measurableTOC andIC background. The user should characterize the backgroundand performance of the degassing module for their application.A removal efficiency of 97 % of the inlet IC is considered

31、satisfactory. Table 1 provides typical IC removal performanceand background levels of the vacuum degassing unit.7. Apparatus7.1 Homogenizing ApparatusA household blender is gen-erally satisfactory for homogenizing immiscible phases inwater.7.2 Apparatus for Carbon DeterminationA typical instru-ment

32、consists of reagent and sample introduction mechanism,reaction vessel, detector, control system, and a display.5Fig. 1shows a diagram of such an arrangement.7.2.1 Vacuum degassing requires the manufacturers mod-ule5that includes a vacuum pump and a hollow fiber mem-brane assembly. Use of this vacuum

33、 degasser will removeessentially all IC as part of the analysis. The membrane moduleconsists of a tube and shell arrangement of microporouspolypropylene hollow fibers. Sample flows along the inside ofthe fibers, while air is passed on the shell side-counterflow tothe sample flow. The shell side pres

34、sure is reduced by means ofa vacuum pump on the air outlet.The sample is acidified beforeintroduction into the degasser to facilitate CO2transportthrough the hollow fibers. Sparging requires an inert vesselwith a capacity of at least double the sample size withprovision for sparging with 50 to 100 m

35、L/min of carbon freegas. This procedure will remove essentially all IC in 2 to 10min, depending on design.7.2.2 ReactionThe sample flow is split after the additionof reagents. Half of the flow passes to the delay coil while theother half passes into the oxidation reactor. The effluent fromboth strea

36、ms passes over individual membranes that allow CO2to pass through the membrane into prepurified water fordetection.4The boldface numbers given in parentheses refer to a list of references at theend of this standard.5Instruments manufactured and marketed by Sievers Instruments, Inc., 2500Central Ave.

37、, Suite H1, Boulder, CO 80301, have been found satisfactory.TABLE 1 Blank Contribution and Inorganic Carbon (IC) RemovalEfficiency of Vacuum Degassing UnitUnit Number g/LATOCBackgroundg/LAICBackgroundIC Level with25 000 g L Input1 3.2 8.2 552 3.2 22 613 2.4 8.0 1054 4.2 13 895 2.8 13 306 3.0 8.0 707

38、 4.8 8.9 678 4.7 8.3 6394.6 1 210 4.7 2.9 72AValues are the difference between before and after addition of the degasser to ahigh purity (5 g/L) water stream.D5904 02 (2017)37.2.3 MembraneThe membrane is a CO2selective fluo-ropolymer that is hydrophobic and non-porous. Refer to thebibliography for a

39、dditional details.7.2.4 DetectorThe CO2that has passed through the mem-brane into the purified water is measured by conductivitysensors. The temperature of the conductivity cell is alsoautomatically monitored so the readings can be corrected forchanges in temperature.7.2.5 Presentation of ResultsThe

40、 conductivity detectoroutput is related to stored calibration data and then displayed asparts per million, (ppm = milligrams of carbon per litre) orparts per billion, (ppb = micrograms of carbon per litre).Valuesare given for TC, IC, and TOC by difference.8. Reagents and Materials8.1 Purity of Reage

41、ntsReagent 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 theAmerican Chemical Society,6wheresuch specifications are available. Other grades may be used,provided it is firs

42、t 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 shall be understood to mean reagent water conformingto Type I or Type II in Specification D1193. The indicateds

43、pecification does not actually specify inorganic carbon ororganic carbon levels. These levels can affect the results of thistest method, especially at progressively lower levels of thecarbon content in the samples to be measured. Where inorganiccarbon in reagent water is significant, CO2-free water

44、may beprepared from reagent water by acidifying to pH 2, thensparging with fritted-glass sparger using CO2-free gas (timewill depend on volume and gas flow rate, and should bedetermined by test). The carbon contribution of the reagentwater should be determined and its effect allowed for inpreparatio

45、n of standards and other solutions. CO2-free watershould be protected from atmospheric contamination. Glasscontainers are required for storage of water and standardsolutions.8.3 Persulfate Reagent (15 % w/v)Prepare ammoniumpersulfate to a concentration of 15 % w/v by dissolving 15 g ofammonium perox

46、ydisulfate in water and diluting to 100 mL.Verify that it contains less than 2000 g/L organic carboncontamination. Certification of reagent assay should be avail-able. Reagents in prepackaged containers from the instrumentmanufacturer have been found to be acceptable.8.4 Acid Reagent (6M)Prepare aci

47、d solution to a concen-tration of 6M and verify that it contains less than 600 g/Lorganic carbon contamination. Since halogens are potentialinterferences, use only sulfuric or phosphoric acid for reagents.Sulfuric acid is prepared by diluting 336 mL of 95 % reagent(sp gr 1.84) to 1 L with reagent wa

48、ter. Phosphoric acid isprepared by diluting 410 mL of 85 % reagent (sp gr 1.69) to 1Lwith water. Certification of reagent assay should be available.Reagents in prepackaged containers from the instrument manu-facturer have been found to be acceptable.8.5 Organic Carbon, Standard Solution (2000 mg/L)C

49、hoose a water-soluble, stable reagent grade compound, suchas benzoic acid or anhydrous potassium hydrogen phthalate(KHC8H4O4). Calculate the weight of compound required tomake 1 L of organic carbon standard solution; for example,KHC8H4O4= 0.471 g of carbon per gram, so 1 L of 2 g/L ofstandard requires 2/0.471, or 4.25, grams of KHP. Dissolve therequired amount of standard in some CO2-free water in a 1-Lvolumetric flask, add 1 mL of sulfuric acid, and dilute tovolume. Dilutions of this stock solution containing 20 mg/Lareto be used to calibrate and te