ASTM D6317-1998(2004) Standard Test Method for Low Level Determination of Total Carbon Inorganic Carbon and Organic Carbon in Water by Ultraviolet Persulfate Oxidation and Membrane.pdf

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1、Designation: D 6317 98 (Reapproved 2004)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 D 6317; the number immedia

2、tely 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This t

3、est 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 D 2777.

4、 Test Method D 5997 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 car

5、bon concentration 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

6、set of 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 respon

7、se of the method over the statedrange of TOC. See Test Method D 4519 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

8、-ment 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 spik

9、ed with 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 D 5997.1.5 This standard does not purport to addres

10、s 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:2D 1129 Terminolo

11、gy Relating to WaterD 1192 Specification for Equipment for Sampling Waterand Steam3D 1193 Specification for Reagent WaterD 2777 Practice for Determination of Precision and Bias ofApplicable Methods of Committee D19 on WaterD 3370 Practices for Sampling Water from Closed ConduitsD 4210 Practice for I

12、ntralaboratory Quality Control Proce-dures and a Discussion on Reporting Low-Level Data3D 5997 Test Method for On-Line Monitoring of Total Car-bon, Inorganic Carbon in Water by Ultraviolet, PersulfateOxidation, and Membrane Conductivity DetectionD 4519 Test Method for Determination of Anions andCarb

13、on Dioxide in High Purity Water by Cation Exchangeand Degassed Cation Conductivity3. Terminology3.1 Definitions For 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 carbondiox

14、ide, 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 Subcommi

15、ttee D19.03 on Sampling of Water andWater-Formed Deposits, Surveillance of Water, and Flow Measurement of Water.Current edition approved Sept. 10, 1998. Published November 1998.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. F

16、or Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.1Copyright 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 oforgan

17、ic compounds.4. Summary of Test Method4.1 Carbon can occur in water as inorganic and organiccompounds. This test method can be used to make 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 dega

18、ssing unit to reduce the ICconcentration as part of the measurement. Alternatively, the ICcan be removed by acidifying and sparging the 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 re

19、maining inorganic carbon to CO2byaction of acid in both channels and oxidation of total carbon toCO2by action of ultraviolet (UV) radiation 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. reactora

20、nd delay coil by the liquid stream and passed throughmembranes that allow the specific passage of CO2to highpurity water where change in 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 bil

21、lion (ppb=g/L). The IC channelreading is subtracted from the TC channel to give a TOCreading. A diagram of suitable apparatus is given in Fig. 1.FIG. 1 Schematic Diagram of TOC Analyzer SystemD 6317 98 (2004)2References 1-54provide additional information on the method.5. Significance and Use5.1 This

22、 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 as a means of monitoringorganic impurities in high purity process water used in indus-tries such

23、 as nuclear power, pharmaceutical, and electronics.6. 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 andwater. Not all suspended or refractory

24、material may be oxi-dized under these conditions; analysts should take steps todetermine what recovery is being obtained. This may be doneby several methods: by rerunning the sample under morevigorous reaction conditions or by spiking samples with knownrefractories and determining recovery.6.2 Chlor

25、ide 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 investigated and found to beminimal under most conditions. Refer to the reference (2) formore information.6.3

26、Note that error will be introduced when the method ofdifference is used to derive a relatively small level from twolarge levels. 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 a

27、nd sparged prior to introduction into the instrument.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, the degassing unit may introduce a measurable TOC andIC background. The

28、user should characterize the backgroundand performance of the degassing module for their application.Table 1 provides typical IC removal 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

29、of analyte areattempted. Throughout this method the analyst must be vigilantfor all potential sources of contamination and must monitorblanks and adjust operations to prevent contamination.7. Apparatus7.1 Apparatus for Carbon DeterminationA typical instru-ment consists of reagent and sample introduc

30、tion mechanism,reaction vessel, detector, control system, and a display.5Fig. 1shows a diagram of such an arrangement.7.1.1 Sampling Needle 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

31、 of the bottle to prevent vacuum build up as thesample is withdrawn. Typically this needle is mounted on anautosampler to provide unattended 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 asse

32、mbly. Use of this vacuum degasserwill remove essentially all IC as part of the analysis. Themembrane module consists of a tube and shell arrangement ofmicroporous polypropylene hollow fibers. Sample flows alongthe inside of the fibers, while air is passed on the shellside-counterflow to the sample f

33、low. The shell side pressure isreduced by means of a vacuum pump on the air outlet. Thesample is acidified before introduction into the degasser tofacilitate CO2transport through the hollow fibers. Spargingrequires an inert vessel with provision for sparging the acidi-fied sample with 50 to 100 mL/m

34、in 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 split 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 p

35、asses over individual membranes that allow CO2to pas through the membrane into prepurified water fordetection.7.1.4 MembraneThe membrane 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

36、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.7.1.6 Data Display The conductivity detector output isrelated to stored calibration data and th

37、en 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, IC, andTOC by difference.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is inten

38、ded that4The 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.TABLE 1 Blank Contribution and IC. Removal

39、 Efficiency ofVacuum Degassing Unit.UnitNo.g/LATOCbackgroundg/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

40、 high purity (5 g/L) water stream.D 6317 98 (2004)3all 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 first ascertained that the reagent is of sufficientpur

41、ity 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 Type II in Specification D 1193. Theindicated specification does not actually specify inorgan

42、iccarbon 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 in reagent water is significant, CO2-free water may be prepared from reagent water by acidifyi

43、ng 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 determined and its effect allowed for inpreparation of standards and other solutions. CO2-free

44、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 bed ion exchange resins may benecessary to maintain an adequately low TOC reagent water.8.3 Per

45、sulfate 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 2000 g/L organiccarbon contamination. Certification of reagent assay should beavailable. Reag

46、ents 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 600 g/Lorganic carbon contamination. Since halogens are potentialinterferences, use only sulfur

47、ic 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 1.69) to 1Lwith water. Certification of reagent assay should be available.Reagents in prepackage

48、d 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 t

49、omake 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. 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 are to be used tocalibrate and test performance of the carbon analyzer.9. Sampling and Sample Preservation9.1 Collect the sample in accordance with SpecificationD 1192 and Practices D 3370.9.2 Samples must be collected in cont