ASTM D5997-96(2005)
(Test Method)Standard Test Method for On-Line Monitoring of Total Carbon, Inorganic Carbon in Water by Ultraviolet, Persulfate Oxidation, and Membrane Conductivity Detection
Standard Test Method for On-Line Monitoring of Total Carbon, Inorganic Carbon in Water by Ultraviolet, Persulfate Oxidation, and Membrane Conductivity Detection
SIGNIFICANCE AND USE
This test method is useful for detecting and determining organic and inorganic carbon impurities in water from a variety of sources including industrial water, drinking water, and waste water.
Measurement of these impurities is of vital importance to the operation of various industries such as power, pharmaceutical, semiconductor, drinking water treatment, and waste treatment. Semiconductor and power applications require measurement of very low organic carbon levels (TOC 1 μg/L). Applications in pharmaceutical industries range from USP purified water (TOC 500 μg/L) to cleaning applications (500 μg/L TOC 50 000 μ g/L). Drinking waters range from 100 μg/L to 25 000 μ g/L and higher. Some of these applications may include waters with substantial ionic impurities as well as organic matter.
Measurement of inorganic carbon as well as total organic carbon is highly important to some applications, such as in the power industry.
Continuous monitoring and observation of trends in these measurements are of interest in indicating the need for equipment adjustment or correction of water purification procedures.
Refer to Annex A1 for additional information regarding the significance of this test method.
SCOPE
1.1 This test method covers the on-line determination of total carbon (TC), inorganic carbon (IC), and total organic carbon (TOC) in water in the range from 0.5 g/L to 50 000 g/L of carbon. Higher carbon levels may be determined by suitable on-line dilution. This test method utilizes ultraviolet-persulfate oxidation of organic carbon coupled with a CO2 selective membrane to recover the CO 2 into deionized water. The change in conductivity of the deionized water is measured and related to carbon concentration in the oxidized sample using calibration data. Inorganic carbon is determined in a similar manner without the requirement for oxidation. In both cases, the sample is acidified to facilitate CO2 recovery through the membrane. The relationship between the conductivity measurement and carbon concentration can be described by a set of chemometric equations for the chemical equilibrium of CO 2, HCO3 , H +, and OH , and the relationship between the ionic concentrations and the conductivity. The chemometric model includes the temperature dependence of the equilibrium constants and the specific conductances resulting in linear response of the method over the stated range of TOC. See Test Method D 4519 for a discussion of the measurement of CO2 by conductivity.
1.2 This test method has the advantage of a very high sensitivity detector that allows very low detection levels on relatively small volumes of sample. Also, the use of two measurement channels allows determination of IC in the sample independently of organic carbon. Isolation of the conductivity detector from the sample by the CO2 selective membrane results in a very stable calibration with minimal interferences.
1.3 This test method was used successfully with reagent water spiked with sodium carbonate and various organic compounds. This test method is effective with both deionized water samples and samples of high ionic strength. It is the user's responsibility to ensure the validity of this test method for waters of untested matrices.
1.4 This test method is applicable only to carbonaceous matter in the sample that can be introduced into the reaction zone. The inlet system generally limits the maximum size of particles that can be introduced. Filtration may also be used to remove particles, however, this may result in removal of organic carbon if the particles contain organic carbon.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D5997–96 (Reapproved 2005)
Standard Test Method for
On-Line Monitoring of Total Carbon, Inorganic Carbon in
Water by Ultraviolet, Persulfate Oxidation, and Membrane
Conductivity Detection
This standard is issued under the fixed designation D5997; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope water samples and samples of high ionic strength. It is the
user’s responsibility to ensure the validity of this test method
1.1 This test method covers the on-line determination of
for waters of untested matrices.
total carbon (TC), inorganic carbon (IC), and total organic
1.4 This test method is applicable only to carbonaceous
carbon (TOC) in water in the range from 0.5 µg/L to 50000
matter in the sample that can be introduced into the reaction
µg/L of carbon. Higher carbon levels may be determined by
zone. The inlet system generally limits the maximum size of
suitable on-line dilution. This test method utilizes ultraviolet-
particles that can be introduced. Filtration may also be used to
persulfate oxidation of organic carbon coupled with a CO
remove particles, however, this may result in removal of
selective membrane to recover the CO into deionized water.
organic carbon if the particles contain organic carbon.
The change in conductivity of the deionized water is measured
1.5 This standard does not purport to address all of the
and related to carbon concentration in the oxidized sample
safety concerns, if any, associated with its use. It is the
using calibration data. Inorganic carbon is determined in a
responsibility of the user of this standard to establish appro-
similar manner without the requirement for oxidation. In both
priate safety and health practices and determine the applica-
cases,thesampleisacidifiedtofacilitateCO recoverythrough
bility of regulatory limitations prior to use.
the membrane. The relationship between the conductivity
measurement and carbon concentration can be described by a
2. Referenced Documents
set of chemometric equations for the chemical equilibrium of
− + −
2.1 ASTM Standards:
CO , HCO ,H , and OH , and the relationship between the
2 3
D1129 Terminology Relating to Water
ionic concentrations and the conductivity. The chemometric
D1192 GuideforEquipmentforSamplingWaterandSteam
model includes the temperature dependence of the equilibrium
in Closed Conduits
constants and the specific conductances resulting in linear
D1193 Specification for Reagent Water
response of the method over the stated range ofTOC. SeeTest
D2777 Practice for Determination of Precision and Bias of
MethodD4519foradiscussionofthemeasurementofCO by
Applicable Test Methods of Committee D19 on Water
conductivity.
D3370 Practices for Sampling Water from Closed Conduits
1.2 This test method has the advantage of a very high
D4519 Test Method for On-Line Determination of Anions
sensitivity detector that allows very low detection levels on
and Carbon Dioxide in High Purity Water by Cation
relatively small volumes of sample. Also, the use of two
Exchange and Degassed Cation Conductivity
measurement channels allows determination of IC in the
sample independently of organic carbon. Isolation of the
3. Terminology
conductivity detector from the sample by the CO selective
3.1 Definitions:
membrane results in a very stable calibration with minimal
3.1.1 For definitions of terms used in this test method, refer
interferences.
to Terminology D1129.
1.3 This test method was used successfully with reagent
3.2 Definitions of Terms Specific to This Standard:
water spiked with sodium carbonate and various organic
3.2.1 inorganic carbon (IC), n—carbon in the form of
compounds. This test method is effective with both deionized
carbon dioxide, carbonate ion, or bicarbonate ion.
1 2
This test method is under the jurisdiction ofASTM Committee D19 on Water For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and is the direct responsibility of Subcommittee D19.03 on Sampling Water and contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Water-Formed Deposits,Analysis of Water for Power Generation and Process Use, Standards volume information, refer to the standard’s Document Summary page on
On-Line Water Analysis, and Surveillance of Water. the ASTM website.
Current edition approved June 1, 2005. Published June 2005. Originally Withdrawn.
approved in 1996. Last previous edition approved in 2000 as D5997–96(2000). Withdrawn. The last approved version of this historical standard is referenced
DOI: 10.1520/D5997-96R05. on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D5997–96 (2005)
3.2.2 refractory material, n—that which cannot be oxidized 6. Interferences and Limitations
completely under the test method conditions.
6.1 The oxidation of dissolved carbon to CO is brought
3.2.3 total carbon (TC), n—the sum of IC and TOC.
about at relatively low temperatures by the chemical action of
3.2.4 total organic carbon (TOC), n—carbon in the form of
reactivespeciesproducedbyUV-irradiatedpersulfateions.Not
organic compounds.
all suspended or refractory material may be oxidized under
these conditions; analysts should take steps to determine what
4. Summary of Test Method
recovery is being obtained. This may be done by several
4.1 Fundamentals—Carbon can occur in water as inorganic
methods: (1) by rerunning the sample under more vigorous
and organic compounds.This test method can be used to make
reaction conditions; (2) by analyzing the sample by an alter-
independent measurements of IC and TC and can also deter-
native method known to result in full recovery; or (3)by
mine TOC as the difference between TC and IC. If IC is high
spiking samples with known refractories and determining
relative to TOC, it is desirable to use a vacuum degassing unit
recovery.
to reduce the IC concentration to obtain meaningful TOC
6.2 Interferences have been investigated and found to be
values by difference.
minimal under most conditions. Chloride ions above 250000
4.2 The basic steps of this test method are:
µg/Lmaycauselowresults.Followthemanufacturer’sinstruc-
4.2.1 Conversion of remaining IC to CO by action of acid,
tions for dealing with high-chloride interference. Other inter-
4.2.2 Removal of IC, if desired, by vacuum degassing,
ferenceshavebeeninvestigatedandfoundtobeminimalunder
4.2.3 Split of flow into two streams to provide for separate
most conditions. The membrane is hydrophobic in nature and
IC and TC measurements,
passes only gaseous materials. Potential interferences are
4.2.4 Oxidation of TC to CO by action of acid-persulfate
nitrite, sulfide, and high levels of hypochlorite or iodine. Refer
aided by ultraviolet (UV) radiation in the TC channel,
to Annex A1 for more information.
4.2.5 Detection of CO by passing each liquid stream over
6.3 Note that error will be introduced when the method of
membranes that allow the specific passage of CO to high-
difference is used to derive a relatively small level from two
purity water where change in conductivity is measured, and
large levels. For example, a water high in IC and low in TOC
4.2.6 Conversion of the conductivity detector signal to a
will give a less precise TOC value as (TC-IC) than by direct
display of carbon concentration in parts per million
measurement. In this case the vacuum degassing unit on the
(ppm=mg/L)orpartsperbillion(ppb=µg/L).TheICchannel
instrument should be used to reduce the concentration of IC
reading is subtracted from the TC channel reading to give a
prior to measurement, or another method of inorganic carbon
TOC reading.Adiagram of suitable apparatus is given in Fig.
removal should be employed.
1.
6.4 Use of the vacuum degassing unit or sparging the
samplerenderstheICreadingmeaninglessandmaycauseloss
5. Significance and Use
of volatile organic compounds, thus yielding a value lower
5.1 This test method is useful for detecting and determining
thanthetrueTOClevel.AtlowTOClevels,thedegassingunit
organicandinorganiccarbonimpuritiesinwaterfromavariety
mayintroduceameasurableTOCandICbackground.Theuser
ofsourcesincludingindustrialwater,drinkingwater,andwaste
should characterize the background and performance of the
water.
degassing module for their applications. Table 1 provides
5.2 Measurement of these impurities is of vital importance
typical IC removal performance and background levels of the
to the operation of various industries such as power, pharma-
vacuum degassing unit.
ceutical, semiconductor, drinking water treatment, and waste
treatment.Semiconductorandpowerapplicationsrequiremea-
7. Apparatus
surement of very low organic carbon levels (TOC < 1 µg/L).
7.1 Apparatus for Carbon Determination—Atypicalinstru-
Applications in pharmaceutical industries range from USP
purified water (TOC < 500 µg/L) to cleaning applications (500 ment consists of reagent and sample introduction mechanism,
reaction vessel, detector, control system, and a display. Fig. 1
µg/L < TOC < 50000 µ g/L). Drinking waters range from <
shows a diagram of such an arrangement.
100 µg/L to 25000 µ g/L and higher. Some of these applica-
tions may include waters with substantial ionic impurities as 7.1.1 Vacuum degassing requires the manufacturer’s mod-
well as organic matter. ule, which includes a vacuum pump and a hollow fiber
5.3 Measurement of inorganic carbon as well as total membraneassembly.Useofthisvacuumdegasserwillremove
organic carbon is highly important to some applications, such essentiallyallICaspartoftheanalysis.Themembranemodule
as in the power industry. consists of a tube and shell arrangement of microporous
5.4 Continuous monitoring and observation of trends in polypropylene hollow fibers. Sample flows along the inside of
these measurements are of interest in indicating the need for the fibers while air is passed on the shell side, counterflow to
equipment adjustment or correction of water purification pro- thesampleflow.Theshellsidepressureisreducedbymeansof
cedures. avacuumpumpontheairoutlet.Thesampleisacidifiedbefore
5.5 Refer toAnnexA1 for additional information regarding introduction into the degasser to facilitate CO transport
the significance of this test method. through the hollow fibers.
D5997–96 (2005)
FIG. 1 Schematic Diagram of TOC Analyzer System
TABLE 1 Blank Contribution and IC Removal Efficiency of
other half passes into the oxidation reactor. The effluent from
Vacuum Degassing Unit
bothstreamspassesoverindividualmembranesthatallowCO
TOC Background, IC Background, IC Level with
to pass through the membrane into prepurified water for
Unit No.
A A
µg/L µg/L 25 000 µg/L Input
detection.
1 3.2 8.2 55
7.1.3 Detector—TheCO thathaspassedthroughthemem-
2 3.2 22 61
brane into the purified water is measured by conductivity
3 2.4 8.0 105
4 4.2 13 89
sensors. The temperature of the conductivity cell is also
5 2.8 13 30
automatically monitored so the readings can be corrected for
6 3.0 8.0 70
changes in temperature.
7 4.8 8.9 67
8 4.7 8.3 63
7.1.4 Membrane—The membrane is a CO selective fluo-
94.6 11 62
ropolymer that is hydrophobic and non-porous. Refer to the
10 4.7 2.9 72
bibliography in Annex A1 for additional details.
A
Values are the difference between, before, and after addition of the degasser
to a high-purity (<5 µg/L) water stream. 7.1.5 Internal Purified Water—Water on the conductivity
sideofthemembraneispurifiedbycontinualpumpingthrough
7.1.2 Reaction—The sample flow is split after the addition a mixed bed ion exchange resin as shown in Fig. 1. On power
of reagents. Half the flow passes to the delay coil while the up, the instrument automatically delays for a period of at least
D5997–96 (2005)
5 min to allow the water in the internal loop to be fully able. Reagents in prepackaged containers from the instrument
deionized. The mixed bed ion exchange resin has an expected manufacturer have been found to be acceptable.
life of several years. See 14.3 for details on monitoring the 8.5 Organic Carbon Solution Standard (2000 mg/L)—
resin. Choose a water-soluble, stable reagent grade compound such
7.1.6 Presentation of Results—The conductivity detector as benzoic acid or anhydrous potassium hydrogen phthalate
outputisrelatedtostoredcalibrationdataandthendisplayedas (KHP, KHC H O ). Calculate the weight of compound re-
8 4 4
parts per million (ppm=mg/L of carbon) or parts per billion quired to make 1 L of organic carbon standard solution; for
(ppb=µg/Lof carbon). Values are given for TC, IC, and TOC example, KHC H O =0.471 g of carbon per gram, so 1 L of
8 4 4
by difference. Data can be maintained on internal nonvolatile 2 g/L of standard requires 2/0.471 or 4.25 g of KHP. Dissolve
RAM, printer tape, or computer storage. the required amount of standard in some CO -free water in a
1-L volumetric flask, add 1 mL of concentrated H SO (sp gr
2 4
8. Reagents and Materials 1.84), and dilute to volume. Dilutions of this stock solution
containing 2 mg/L are to be used to calibrate and test
8.1 Purity of Reagents—Use reagent grade chemicals in all
performance of the carbon analyzer.
tests.Unlessotherwiseindicated,itisintendedthatallreagents
8.6 Inorganic Carbon Solution Standard (2000 mg/L)—
conform to the specifications of the Committee on Analytical
5 Choose a water soluble, stable, reagent grade compound such
Reagents of the American Chemical Society, where such
as sodium carbonate (Na CO ). Calculate the weight required
2 3
specifications are available. Other grades may be used, pro-
tomake1Lofstandardsolution;forexample,Na CO =0.113
2 3
videditisfirstascertainedthatthereagentisofsufficientpurity
gofcarbonperg,so1Lof2g/Lofstandardrequiring2/0.113
to permit its use without lessening the accuracy of the
or17.7gofNa CO .Dissolvetherequiredamountofstandard
2 3
determination.
in CO -free water ina1Lvolumetric flask. Keep this solution
8.2 Purity of Water—Unlessotherwiseindicated,references
tightly sealed and do not add acid. Use dilutions of this stock
towatershallbeunderstoodtomeanreagentwaterconforming
solutioncontaining2mg/Ltocalibrateandtestperformanceof
to Specification D1193, Type I or Type II. The indicated
the carbon analyzer.
specification does not actually specify inorganic carbon or
organiccarbonlevels.Theselevelscanaffecttheresultsofthis
9. Sampling
test method, especially at progressively lower levels of the
9.1 Collect the sample in accordance with Specification
carbo
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