ASTM D6317-1998(2009) 9375 Standard Test Method for Low Level Determination of Total Carbon Inorganic Carbon and Organic Carbon in Water by Ultraviolet Persulfate Oxidation and Mem.pdf

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1、Designation: D6317 98 (Reapproved 2009)Standard Test Method forLow Level Determination of Total Carbon, Inorganic Carbonand Organic Carbon in Water by Ultraviolet, PersulfateOxidation, and Membrane Conductivity Detection1This standard is issued under the fixed designation D6317; the number immediate

2、ly following the designation 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

3、 method covers the determination of totalcarbon (TC), inorganic carbon (IC), and total organic carbon(TOC) in water in the range from 10 to 1000 g/L of carbon.This method is for laboratory or grab sample applications andhas been subjected to an interlaboratory study under theguidelines of D2777. Tes

4、t Method D5997 can be used foron-line determinations. The test method utilizes persulfate orultraviolet oxidation of organic carbon, or both coupled with aCO2selective membrane to recover the CO2into deionizedwater. The change in conductivity of the deionized water ismeasured and related to carbon c

5、oncentration in the oxidizedsample. Inorganic carbon is determined in a similar mannerwithout the oxidation step. In both cases, the sample isacidified to facilitate CO2recovery through the membrane. Therelationship between the conductivity measurement and carbonconcentration is described by a set o

6、f chemometric equationsfor the chemical equilibrium of CO2, HCO3, and H+, and therelationship between the ionic concentrations and the conduc-tivity. The chemometric model includes the temperature de-pendence of the equilibrium constants and the specific conduc-tances resulting in linear response of

7、 the method over the statedrange of TOC. See Test Method D4519 for a discussion of themeasurement of CO2by conductivity.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

8、channels allows determination 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 wit

9、h various organic materials. It is the usersresponsibility to ensure the validity of this test method forwaters of untested matrices.1.4 In addition to laboratory analyses, this test method maybe adapted to on line monitoring. See Test Method D5997.1.5 This standard does not purport to address all o

10、f 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 Terminology Relat

11、ing to WaterD1192 Guide for Equipment for Sampling Water and Steamin Closed Conduits3D1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD4210 Practice fo

12、r Intralaboratory Quality Control Proce-dures and a Discussion on Reporting Low-Level Data3D5997 Test Method for On-Line Monitoring of Total Car-bon, Inorganic Carbon in Water by Ultraviolet, PersulfateOxidation, and Membrane Conductivity DetectionD4519 Test Method for On-Line Determination of Anion

13、sand Carbon Dioxide in High Purity Water by CationExchange and Degassed Cation Conductivity3. Terminology3.1 Definitions For definitions of terms used in this testmethod, refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 inorganic carbon (IC)carbon in the form of ca

14、rbondioxide, carbonate ion, or bicarbonate ion.3.2.2 refractory materialthat which cannot be oxidizedcompletely under the test method conditions.3.2.3 total carbon (TC)the sum of IC and TOC.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of

15、Subcommittee D19.03 on Sampling Water andWater-Formed Deposits, Analysis of Water for Power Generation and Process Use,On-Line Water Analysis, and Surveillance of Water.Current edition approved Oct. 1, 2009. Published November 2009. DOI:10.1520/D6317-98R09.2For referenced ASTM standards, visit the A

16、STM 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.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.1Copyrigh

17、t ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.4 total organic carbon (TOC)carbon in the form oforganic compounds.4. Summary of Test Method4.1 Carbon can occur in water as inorganic and organiccompounds. This test method can be used to m

18、ake independentmeasurements of IC and TC and can also determine TOC as thedifference of TC and IC. If IC is high relative to TOC it isdesirable to use a vacuum degassing unit to reduce the ICconcentration as part of the measurement. Alternatively, the ICcan be removed by acidifying and sparging the

19、sample prior toinjection into the instrument. The basic steps of the procedureare as follows:(1) Removal of IC, if desired, by vacuum degassing;(2) Conversion of remaining inorganic carbon to CO2byaction of acid in both channels and oxidation of total carbon toCO2by action of ultraviolet (UV) radiat

20、ion in the TC channel.(Acid-persulfate can be added but is usually not required atTOC levels below 1 ppm).(3) Detection of CO2that is swept out of the U.V. reactorand delay coil by the liquid stream and passed throughmembranes that allow the specific passage of CO2to highpurity water where change in

21、 conductivity is measured and;(4) Conversion of the conductivity detector signal to adisplay of carbon concentration in parts per million(ppm=mg/L) or parts per billion (ppb=g/L). The IC channelreading is subtracted from the TC channel to give a TOCreading. A diagram of suitable apparatus is given i

22、n Fig. 1.FIG. 1 Schematic Diagram of TOC Analyzer SystemD6317 98 (2009)2References 1-54provide additional information on the method.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 m

23、ost common form, this test methodis used to measure organic carbon as a means of monitoringorganic impurities in high purity process water used in indus-tries such as nuclear power, pharmaceutical, and electronics.6. Interferences and Limitations6.1 The oxidation of dissolved carbon to CO2is brought

24、about at relatively low temperatures by the chemical action ofreactive species produced by UV-irradiated persulfate ions andwater. Not all suspended or refractory material may be oxi-dized under these conditions; analysts should take steps todetermine what recovery is being obtained. This may be don

25、eby several methods: by rerunning the sample under morevigorous reaction conditions or by spiking samples with knownrefractories and determining recovery.6.2 Chloride ion above 250 mg/L tends to interfere withoxidative reaction mechanisms in this test method. Followmanufacturers instructions for dea

26、ling with this problem.Other interferences have been investigated and found to beminimal under most conditions. Refer to the reference (2) 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. In this

27、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.6.4 Use of the vacuum degassing unit or sparging thesample may cause loss of volatil

28、e organic compounds, thusyielding a value lower than the true TOC level. At low TOClevels, the degassing unit may introduce a measurable TOC andIC background. The user should characterize the backgroundand performance of the degassing module for their application.Table 1 provides typical IC removal

29、performance and back-ground levels of the vacuum degassing unit.6.5 Contamination of the sample with both CO2and organiccarbon is a severe problem as lower levels of analyte areattempted. Throughout this method the analyst must be vigilantfor all potential sources of contamination and must monitorbl

30、anks and adjust operations to prevent contamination.7. Apparatus7.1 Apparatus for Carbon DeterminationA typical instru-ment consists of reagent and sample introduction mechanism,reaction vessel, detector, control system, and a display.5Fig. 1shows a diagram of such an arrangement.7.1.1 Sampling Need

31、le A double chambered needle ca-pable of piercing the sample bottle septum and pulling samplefrom the bottom of the bottle is used. The second chambervents the top of the bottle to prevent vacuum build up as thesample is withdrawn. Typically this needle is mounted on anautosampler to provide unatten

32、ded analysis of several samples.7.1.2 I.C. Removal Vacuum degassing requires the manu-facturers module5which includes a vacuum pump and ahollow fiber membrane assembly. Use of this vacuum degasserwill remove essentially all IC as part of the analysis. Themembrane module consists of a tube and shell

33、arrangement ofmicroporous polypropylene hollow fibers. Sample flows alongthe inside of the fibers, while air is passed on the shellside-counterflow to the sample flow. The shell side pressure isreduced by means of a vacuum pump on the air outlet. Thesample is acidified before introduction into the d

34、egasser tofacilitate CO2transport through the hollow fibers. Spargingrequires an inert vessel with provision for sparging the acidi-fied sample with 50 to 100 mL/min of carbon free gas. Thisprocedure will remove essentially all IC in 2 to 10 min,depending on design.7.1.3 ReactorThe sample flow is sp

35、lit after the addition ofreagents. 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 pas through the membrane into prepurified water fordetection.7.1.4 MembraneThe membrane

36、is a CO2selective fluo-ropolymer which is hydrophobic and non-porous. Refer to thebibliography for additional details.7.1.5 DetectorThe CO2that has passed through the mem-brane into the purified water is measured by conductivitysensors. The temperature of the conductivity cell is alsoautomatically m

37、onitored so the readings can be corrected forchanges in temperature.7.1.6 Data Display The conductivity detector output isrelated to stored calibration data and then displayed as parts permillion, (ppm = mg of carbon per litre) or parts per billion,(ppb = g of carbon per L). Values are given for TC,

38、 IC, andTOC by difference.4The boldface numbers in parentheses refer to the list of references found at theend of this test method.5Instruments manufactured and marketed by Sievers Instruments, Inc., 6185Arapahoe Ave., Suite H1, Boulder, CO 80303 have been found satisfactory. If youare aware of alte

39、rnative suppliers, please provide this information to ASTMInternational Headquarters. Your comments will receive careful consideration at ameeting of the responsible technical committee,1which you may attend.TABLE 1 Blank Contribution and IC. Removal Efficiency ofVacuum Degassing Unit.UnitNo.g/LATOC

40、backgroundg/LAICbackgroundIC level with 25 000g/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.D6317 98 (2009)3

41、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 theAmerican Chemical Society,6wheresuch specifications are available.

42、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 Water Unless otherwise indicated, refer-ences to water shall be understood to mean reagent waterconforming to Type I or

43、 Type II in Specification D1193. Theindicated specification does not actually specify inorganiccarbon or organic carbon levels. These levels can affect theresults of this test method, especially at progressively lowerlevels of the carbon content in the samples to be measured.Where inorganic carbon i

44、n reagent water is significant, CO2-free water may be prepared from reagent water by acidifying topH 2, then sparging with fritted-glass sparger using CO2-freegas (time will depend on volume and gas flow rate, and shouldbe determined by test). The carbon contribution of the reagentwater should be de

45、termined and its effect 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. Continuous U.V. treatment of water with recyclingthrough appropriate mixed be

46、d ion exchange resins may benecessary to maintain an adequately low TOC reagent water.8.3 Persulfate Reagent (15 % w/v)Prepare ammoniumpersulfate solution to a concentration of 15 % w/v by dissolv-ing 15 g of ammonium peroxydisulfate in water and diluting to100 mL. Verify that it contains less than

47、2000 g/L organiccarbon contamination. Certification of reagent assay should beavailable. Reagents in prepackaged containers from the instru-ment manufacturer have been found to be acceptable.8.4 Acid Reagent (6M)Prepare acid solution to a concen-tration of 6M and verify that it contains less than 60

48、0 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 water. Phosphoric acid isprepared by diluting 410 mL of 85 % reagent (sp gr 1.6

49、9) 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 (1000 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 g, so one L of 1 g/L ofstandard requires 1/0.471, or 2.12, grams of KHP. Di