1、Designation: D 5904 02Standard Test Method forTotal Carbon, Inorganic Carbon, and Organic Carbon inWater by Ultraviolet, Persulfate Oxidation, and MembraneConductivity Detection1This standard is issued under the fixed designation D 5904; the number immediately following the designation indicates the
2、 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of total
3、carbon (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 organic car-bon, coupled with a CO2selective membrane to recover theCO
4、2into 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 CO2recovery th
5、roughthe 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 includesthe t
6、emperature 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 determination of CO2in t
7、he 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 various organic
8、materials. 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 maximumsize of
9、particles that can be introduced.1.5 In addition to laboratory analyses, this test method maybe applied to on line monitoring.1.6 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 ap
10、pro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 1129 Terminology Relating to Water2D 1192 Specification for Equipment for Sampling Waterand Steam in Closed Conduits2D 1193 Specification for Rea
11、gent Water2D 2777 Practice for Determination of Precision and Bias ofApplicable Methods of Committee D19 on Water2D 3370 Practices for Sampling Water from Closed Con-duits2D 5810 Guide for Spiking Into Aqueous Samples2D 5847 Practice for Writing Quality Control Specificationsfor Standard Test Method
12、s for Water Analysis33. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D 1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 inorganic carbon (IC)carbon in the form of carbondioxide, carbonate ion, or bicarbonate ion.3.2.2 potassium hydroge
13、n phthalate (KHP)KHC8H4O4.3.2.3 refractory materialthat which cannot be oxidizedcompletely under the test method conditions.3.2.4 total carbon (TC)the sum of IC and TOC.3.2.5 total organic carbon (TOC)carbon in the form oforganic compounds.4. Summary of Test Method4.1 FundamentalsCarbon can occur in
14、 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 relative1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibi
15、lity of Subcommittee D19.06 on Methods forAnalysis forOrganic Substances in Water.Current edition approved July 10, 2002. Published July 2002. Originallypublished as D 590496. Last previous edition D 590496.2Annual Book of ASTM Standards, Vol 11.01.3Annual Book of ASTM Standards, Vol 11.02.1Copyrigh
16、t ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.to TOC it is desirable to use a vacuum degassing unit to reducethe IC concentration as part of the measurement. Alternatively,the IC can be removed by acidifying and sparging the sampleprior to
17、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 Conversion of remaining inorganic carbon to CO2byaction of acid in both channels and oxidation of total carbon toCO2by action of acid-persulfate, aided by ultraviolet
18、(UV)radiation in the TC channel;4.2.3 Detection of CO2that is swept out of the 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 carbo
19、n concentration in parts per million (ppm = mg/L) or parts per billion (ppb = g/L). The IC channelFIG. 1 Schematic Diagram of TOC Analyzer SystemTABLE 1 Blank Contribution and Inorganic Carbon (IC) RemovalEfficiency of Vacuum Degassing UnitUnit Number g/LATOCBackgroundg/LAICBackgroundIC Level with25
20、 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 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 toa high purity (5 g/L) water stream.D 5904 022reading is subtracted from the TC channel to gi
21、ve 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 water from a variety of natural, domestic, andindustrial sources. In it
22、s 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 relationship of TOC to other water quality param-eters such as chemical o
23、xygen demand (COD) and total oxygendemand (TOD) is described in the literature.56. Interferences and Limitations6.1 The oxidation of dissolved carbon to CO2is broughtabout at relatively low temperatures by the chemical action ofreactive species produced by UV-irradiated persulfate ions. Notall suspe
24、nded 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 conditions; by analyzing the sample by an alternativemethod known to re
25、sult 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 instructions for dealing with this problem.Other interferences have been investig
26、ated 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. For example, a ground water high in IC and lowin TOC will give a poorer
27、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 prior to introduction into the instrument. Useof the vacuum degassing
28、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, thusyielding a value lower than the true TOC level. At low TOClevels, t
29、he 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 consideredsatisfactory. Table 1 provides typical IC removal performanceand backgr
30、ound levels of the vacuum degassing unit.7. Apparatus7.1 Homogenizing ApparatusAhousehold blender is gen-erally satisfactory for homogenizing immiscible phases inwater.7.2 Apparatus for Carbon DeterminationAtypical instru-ment consists of reagent and sample introduction mechanism,reaction vessel, de
31、tector, control system, and a display.6Fig. 1shows a diagram of such an arrangement.7.2.1 Vacuum degassing requires the manufacturers mod-ule6that includes a vacuum pump and a hollow fiber mem-brane assembly. Use of this vacuum degasser will removeessentially all IC as part of the analysis. The memb
32、rane 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 pressure is reduced by means ofa vacuum pump on the air outlet.The sample is
33、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 mL/min of carbon freegas. This procedure will remove essentially all IC in
34、 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 streams passes over individual membranes that allow CO2to pass through the mem
35、brane into prepurified water fordetection.7.2.3 MembraneThe membrane is a CO2selective fluo-ropolymer that is hydrophobic and non-porous. Refer to thebibliography for additional details.7.2.4 DetectorThe CO2that has passed through the mem-brane into the purified water is measured by conductivitysens
36、ors. The temperature of the conductivity cell is alsoautomatically monitored so the readings can be corrected forchanges in temperature.7.2.5 Presentation of ResultsThe conductivity detectoroutput is related to stored calibration data and then displayed asparts per million, (ppm = milligrams of carb
37、on 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 ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the spe
38、cifications of the Committee onAnalytical Reagents of theAmerican Chemical Society,7wheresuch specifications are available. Other grades may be used,4The boldface numbers given in parentheses refer to a list of references at theend of this standard.5Handbook for Monitoring Industrial Wastewater, Sec
39、tion 5.3, U.S. Environ-mental Protection Agency, August 1973, pp. 512.6Instruments manufactured and marketed by Sievers Instruments, Inc., 2500Central Ave., Suite H1, Boulder, CO 80301, have been found satisfactory.7Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Societ
40、y, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.D
41、 5904 023provided 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 shall be understood to mean reagent water conformingto Type I or Type II in Specifi
42、cation D 1193. The indicatedspecification 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
43、 significant, CO2-free water 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 ef
44、fect allowed for inpreparation 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 dis
45、solving 15 g ofammonium peroxydisulfate 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
46、 Acid Reagent (6M)Prepare acid 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
47、 1.84) to 1 L with reagent water. 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, S
48、tandard Solution (2000 mg/L)Choose 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
49、 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 test performance of the carbonanalyzer.9. Sampling and Sample Preservation9.1 Collect the sample in accordance with SpecificationD 1192 and Practices D 3370.9.2 To preserve samples for this analysis, store samples inglass at 4C. To aid preservation, acidify the samples to a p
