ASTM D5997-96(2000)
(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
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 CO2 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 CO 2 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 CO2, 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 D4519 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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An American National Standard
Designation:D 5997–96 (Reapproved 2000)
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 D 5997; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope user’s responsibility to ensure the validity of this test method
for waters of untested matrices.
1.1 This test method covers the on-line determination of
1.4 This test method is applicable only to carbonaceous
total carbon (TC), inorganic carbon (IC), and total organic
matter in the sample that can be introduced into the reaction
carbon (TOC) in water in the range from 0.5 µg/L to 50000
zone. The inlet system generally limits the maximum size of
µg/L of carbon. Higher carbon levels may be determined by
particles that can be introduced. Filtration may also be used to
suitable on-line dilution. This test method utilizes ultraviolet-
remove particles, however, this may result in removal of
persulfate oxidation of organic carbon coupled with a CO
organic carbon if the particles contain organic carbon.
selective membrane to recover the CO into deionized water.
1.5 This standard does not purport to address all of the
The change in conductivity of the deionized water is measured
safety concerns, if any, associated with its use. It is the
and related to carbon concentration in the oxidized sample
responsibility of the user of this standard to establish appro-
using calibration data. Inorganic carbon is determined in a
priate safety and health practices and determine the applica-
similar manner without the requirement for oxidation. In both
bility of regulatory limitations prior to use.
cases, the sample is acidified to facilitate CO recovery
through the membrane. The relationship between the conduc-
2. Referenced Documents
tivity measurement and carbon concentration can be described
2.1 ASTM Standards:
byasetofchemometricequationsforthechemicalequilibrium
− + −
D 1129 Terminology Relating to Water
of CO , HCO ,H , and OH , and the relationship between
2 3
D 1192 Specification for Equipment for Sampling Water
theionicconcentrationsandtheconductivity.Thechemometric
and Steam in Closed Conduits
model includes the temperature dependence of the equilibrium
D 1193 Specification for Reagent Water
constants and the specific conductances resulting in linear
D2777 PracticefortheDeterminationofPrecisionandBias
response of the method over the stated range ofTOC. SeeTest
ofApplicableTest Methods of Committee D-19 onWater
MethodD4519foradiscussionofthemeasurementofCO by
D 3370 Practices for Sampling Water from Closed Con-
conductivity.
duits
1.2 This test method has the advantage of a very high
D 4519 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.
water samples and samples of high ionic strength. It is the
3.2.2 refractory material, n—that which cannot be oxidized
completely under the test method conditions.
3.2.3 total carbon (TC), n—the sum of IC and TOC.
This test method is under the jurisdiction ofASTM Committee D-19 on Water
and is the direct responsibility of Subcommittee D19.03 on Sampling of Water and
Water-Formed Deposits, Surveillance of Water, and Flow Measurement of Water.
Current edition approved July 10, 1996. Published November 1996. Annual Book of ASTM Standards, Vol 11.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 5997–96 (2000)
3.2.4 total organic carbon (TOC), n—carbon in the form of 4.2.2 Removal of IC, if desired, by vacuum degassing,
organic compounds.
4.2.3 Split of flow into two streams to provide for separate
IC and TC measurements,
4. Summary of Test Method
4.2.4 Oxidation of TC to CO by action of acid-persulfate
4.1 Fundamentals—Carboncanoccurinwaterasinorganic
aided by ultraviolet (UV) radiation in the TC channel,
and organic compounds.This test method can be used to make
4.2.5 Detection of CO by passing each liquid stream over
independent measurements of IC and TC and can also deter-
membranes that allow the specific passage of CO to high-
mine TOC as the difference between TC and IC. If IC is high 2
purity water where change in conductivity is measured, and
relative to TOC, it is desirable to use a vacuum degassing unit
to reduce the IC concentration to obtain meaningful TOC
4.2.6 Conversion of the conductivity detector signal to a
values by difference.
display of carbon concentration in parts per million
4.2 The basic steps of this test method are:
(ppm=mg/L)orpartsperbillion(ppb=µg/L).TheICchannel
4.2.1 Conversion of remaining IC to CO by action of acid,
FIG. 1 Schematic Diagram of TOC Analyzer System
D 5997–96 (2000)
reading is subtracted from the TC channel reading to give a 6.4 Use of the vacuum degassing unit or sparging the
TOC reading.Adiagram of suitable apparatus is given in Fig. samplerenderstheICreadingmeaninglessandmaycauseloss
1. of volatile organic compounds, thus yielding a value lower
thanthetrueTOClevel.AtlowTOClevels,thedegassingunit
5. Significance and Use
mayintroduceameasurableTOCandICbackground.Theuser
5.1 This test method is useful for detecting and determining
should characterize the background and performance of the
organicandinorganiccarbonimpuritiesinwaterfromavariety
degassing module for their applications. Table 1 provides
ofsourcesincludingindustrialwater,drinkingwater,andwaste
typical IC removal performance and background levels of the
water.
vacuum degassing unit.
5.2 Measurement of these impurities is of vital importance
7. Apparatus
to the operation of various industries such as power, pharma-
ceutical, semiconductor, drinking water treatment, and waste
7.1 Apparatus for Carbon Determination—Atypicalinstru-
treatment.Semiconductorandpowerapplicationsrequiremea-
ment consists of reagent and sample introduction mechanism,
surement of very low organic carbon levels (TOC < 1 µg/L).
reaction vessel, detector, control system, and a display. Fig. 1
Applications in pharmaceutical industries range from USP
shows a diagram of such an arrangement.
purified water (TOC < 500 µg/L) to cleaning applications (500
7.1.1 Vacuum degassing requires the manufacturer’s mod-
µg/L
ule, which includes a vacuum pump and a hollow fiber
µg/L to 25000 µg/L and higher. Some of these applications
membraneassembly.Useofthisvacuumdegasserwillremove
may include waters with substantial ionic impurities as well as
essentiallyallICaspartoftheanalysis.Themembranemodule
organic matter.
consists of a tube and shell arrangement of microporous
5.3 Measurement of inorganic carbon as well as total
polypropylene hollow fibers. Sample flows along the inside of
organic carbon is highly important to some applications, such
the fibers while air is passed on the shell side, counterflow to
as in the power industry.
thesampleflow.Theshellsidepressureisreducedbymeansof
5.4 Continuous monitoring and observation of trends in
avacuumpumpontheairoutlet.Thesampleisacidifiedbefore
these measurements are of interest in indicating the need for
introduction into the degasser to facilitate CO transport
equipment adjustment or correction of water purification pro-
through the hollow fibers.
cedures.
7.1.2 Reaction—The sample flow is split after the addition
5.5 Refer toAnnexA1 for additional information regarding
of reagents. Half the flow passes to the delay coil while the
the significance of this test method.
other half passes into the oxidation reactor. The effluent from
bothstreamspassesoverindividualmembranesthatallowCO
6. Interferences and Limitations
to pass through the membrane into prepurified water for
6.1 The oxidation of dissolved carbon to CO is brought
2 detection.
about at relatively low temperatures by the chemical action of
7.1.3 Detector—TheCO thathaspassedthroughthemem-
reactivespeciesproducedbyUV-irradiatedpersulfateions.Not
brane into the purified water is measured by conductivity
all suspended or refractory material may be oxidized under
sensors. The temperature of the conductivity cell is also
these conditions; analysts should take steps to determine what
automatically monitored so the readings can be corrected for
recovery is being obtained. This may be done by several
changes in temperature.
methods: (1) by rerunning the sample under more vigorous
7.1.4 Membrane—The membrane is a CO selective fluo-
reaction conditions; (2) by analyzing the sample by an alter-
ropolymer that is hydrophobic and non-porous. Refer to the
native method known to result in full recovery; or (3)by
bibliography in Annex A1 for additional details.
spiking samples with known refractories and determining
7.1.5 Internal Purified Water—Water on the conductivity
recovery.
sideofthemembraneispurifiedbycontinualpumpingthrough
6.2 Interferences have been investigated and found to be
a mixed bed ion exchange resin as shown in Fig. 1. On power
minimal under most conditions. Chloride ions above 250000
up, the instrument automatically delays for a period of at least
µg/Lmaycauselowresults.Followthemanufacturer’sinstruc-
tions for dealing with high-chloride interference. Other inter-
TABLE 1 Blank Contribution and IC Removal Efficiency of
ferenceshavebeeninvestigatedandfoundtobeminimalunder
Vacuum Degassing Unit
most conditions. The membrane is hydrophobic in nature and
TOC Background, IC Background, µg/ IC Level with
passes only gaseous materials. Potential interferences are Unit No.
A A
µg/L L 25 000 µg/L Input
nitrite, sulfide, and high levels of hypochlorite or iodine. Refer
1 3.2 8.2 55
to Annex A1 for more information.
2 3.2 22 61
3 2.4 8.0 105
6.3 Note that error will be introduced when the method of
4 4.2 13 89
difference is used to derive a relatively small level from two
5 2.8 13 30
large levels. For example, a water high in IC and low in TOC
6 3.0 8.0 70
7 4.8 8.9 67
will give a less precise TOC value as (TC-IC) than by direct
8 4.7 8.3 63
measurement. In this case the vacuum degassing unit on the
94.6 11 62
instrument should be used to reduce the concentration of IC
10 4.7 2.9 72
prior to measurement, or another method of inorganic carbon A
Values are the difference between, before, and after addition of the degasser
removal should be employed. to a high-purity (<5 µg/L) water stream.
D 5997–96 (2000)
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 Lof
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
3 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-
to make 1 L of standard solution; for example, Na CO
videditisfirstascertainedthatthereagentisofsufficientpurity
3=0.113 g of carbon per g, so 1 L of 2 g/L of standard
to permit its use without lessening the accuracy of the
requiring 2/0.113 or 17.7 g of Na CO . Dissolve the required
2 3
determination.
amountofstandardinCO -freewaterina1Lvolumetricflask.
8.2 Purity of Water— Unless otherwise indicated, refer-
Keep this solution tightly sealed and do not add acid. Use
ences to water shall be understood to mean reagent water
dilutions of this stock solution containing 2 mg/L to calibrate
conforming to Specification D1193, Type I or Type II. The
and test performance of the carbon analyzer.
indicated specification does not actually specify inorganic
carbon or organic carbon levels. These levels can affect the
9. Sampling
results of this test method, especially at progressively lower
levels of the carbon content in the samples to be measured. 9.1 Collect the sample in accordance with Specification
Whereinorganiccarboninreagentwaterissignificant,prepare D1192 and Practices D3370.
CO -free water from reagent water by acidifying to pH 2 and
sparge with fritted-glass sparger using CO -free gas (time will
10. Instrument Operation
depend on volume and gas flow rate and should be determined
10.1 Follow the manufacturer’s instructions fo
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