Hanna Instruments HI 4105 User manual

1
HI 4105HI 4105
HI 4105HI 4105
HI 4105
CarbonDioxide
Ion
SelectiveElectrode
Instruction Manual
CARBON DIOXIDE
HI 4105

2

3
HI 4105 Carbon Dioxide ElectrodeHI 4105 Carbon Dioxide Electrode
HI 4105 Carbon Dioxide ElectrodeHI 4105 Carbon Dioxide Electrode
HI 4105 Carbon Dioxide Electrode
I.I.
I.I.
I. Introduction:Introduction:
Introduction:Introduction:
Introduction:
TheHannaHI4105CarbonDioxide gassensingelectrode
isacombinationelectrodedesignedforthemeasurement
ofCarbonDioxideinaqueoussolutionssuchaswater,soft
drinksorwine,samples. CarbonateandBicarbonateions
are also measured by conversion to Carbon Dioxide gas
upon ISA addition.
II.II.
II.II.
II. SpecificationsSpecifications
SpecificationsSpecifications
Specifications
Type: CO2gas sensing
electrodewithglasspH
internal, Ag/ AgCl
referenceandgas
permeable membrane.
Speciesdetected: CO32-,HCO3-,CO2
CO2MeasurementRange: 0.02Mto4x10-4M
880to17.6ppm
Interferingions: SO2/SO32-, H2S/S2-
Operating Temperature: 0to40°C
Operating pH: 4-5 pH
Dimensions: 12mm(OD)X120
mm (insertion)
0.47”x4.72”
Wettedmaterials: Delrin®, body and cap
with PTFE membrane
Connection: BNC

4
III.III.
III.III.
III. Theory of OperationTheory of Operation
Theory of OperationTheory of Operation
Theory of Operation:::::
TheCarbonDioxideelectrodeisacompletepotentiometric
cell that contains both a silver/silver chloride (Ag/AgCl)
referenceandapHmeasurementelement. Theseelements
arehousedwithina thermoplastic body in achlorideion-
containingelectrolyte,andareisolatedfromthesampleby
a PTFE membrane.
ISA addition changes the pH of the sample to approxi-
mately 4.7 pH and Bicarbonate (HCO3-) and carbonate
(CO32-)ionsinthesampleareconverted tocarbondioxide
(CO2). TheCO2inthesamplesolutiondiffusesthroughthe
PTFEmembranewhereitdissolvesintothethinfilmoffill
solutionfoundbetweenthemembraneandtheinternalpH
membrane. Here it converts back into bicarbonate and
hydrogen ions. The pH changes proportionally with the
concentrationofdissolvedgasinthesamplesolution.Dif-
fusionofCO2continuesuntilthepartialpressuresofthegas
in the sample and thin film are equal.
The Nernst expression for an Carbon Dioxide sensor is ex-
pressedintheequationbelow.Notethatthepotentialisa
functionoftheCarbonDioxidegas,whichinturnisrelated
tothehydrogenionconcentration. Theglassinternal,
Ag/AgCl reference, equilibrium constant and Henry’s law
constant are rolled into the E’and Eoterms. The Nernst
equationforthesensorbecomestheequationnotedbelow:
E = E’+2.3RT/nF log [CO2]= Eo+0.059 log [H+]
E = observed potential
E’= Reference and fixed internal voltages
R = gas constant (8.314 J/K Mol)
n= Charge on ion (equivalents/mol)
T = absolute temperature in K
F = Faraday constant (9.648 x 104 C/equivalent)
ThemV should increase in aNernstian manner as the
carbondioxidepartialpressure increases inthesample.

5
Membrane/membrane cap
IV.IV.
IV.IV.
IV. Design ElementsDesign Elements
Design ElementsDesign Elements
Design Elements
The HannaHI4105CarbonDioxidegassensorhas3main
parts.These arethemembrane/membranecap,outer probe
bodywithantirotationkeyandthepH/referenceassembly
which includes the outer electrode cap, spring, inner cap
andpH/referenceelectrodeassembly.
Outerprobebody
antirotationkey innercap
pH/referenceelectrodeassembly
spring
outerelectrode
cap
pH
sensitive
membrane
Reference
electrode
cable
O-ring

6
V.V.
V.V.
V. Equipment Required:Equipment Required:
Equipment Required:Equipment Required:
Equipment Required:
•Hanna HI 4222 pH/ISE/mV meter or other suitable
ionorpH/mVmeter.(Note:log/lineargraphpaperis
useful if an ISE meter is not available).
•Hanna HI 180 magnetic stirrer or equivalent with
stirringbars.(Note:Isolatebeakersfromstirrermotor
heat by placing insulating material such as foam or
corkbetweenthem).
•HannaHI4000-71gassensortestvessel or
HannaHI76404electrodeholderorequivalentwith
Beakers or other suitable measurement vessel with
plasticsealing film orwrap.
VI.VI.
VI.VI.
VI. Solutions Required for Calibration:Solutions Required for Calibration:
Solutions Required for Calibration:Solutions Required for Calibration:
Solutions Required for Calibration:
IonicStrengthAdjuster(ISA),500mL: HI4005-00
Hanna0.1M standard, 500mL: HI4005-01
Hanna 1000 ppm CO2standard, 500 mL: HI4005-03*
*PleaseNote: ThiscalibrationstandardsisppmasCaCO3
See Section XVII for additional solutions and accessories
used for maintenance.
Using volumetric pipettes and glassware prepare serial
dilutions of the standard. Select concentrations that will
approximatelybrackettheconcentrationofthesamplesto
bemeasured. Standardswith concentrations lessthan
10-3M shouldbepreparedfreshdaily. Storesolutionina
tightlysealed bottlewithoutISAadded.10mLofHI4005-
00ISA should be added toeach 100 mL sample ofstan-
dardandsamplesjustpriortomeasurement. ISAadjusts
the pH of the sample or standard to about pH 4.7 thus
convertingcarbonateand bicarbonate ion to carbondiox-
ide. It also provides samples and standards a constant
ionicstrengthbackgroundthatstabilizesthesolutionsac-
tivitycoefficientandpermitsconcentrationtobemeasured
directly.

7
VIIVII
VIIVII
VII. General GuidelinesGeneral Guidelines
General GuidelinesGeneral Guidelines
General Guidelines
•Calibration standards and sample solutions should
havethesameionicstrength.ISAshouldbeaddedto
bothsamplesandstandardsimmediatelybeforetak-
ing measurements.
• Calibrationstandardsandsamplesolutionsshouldbe
stirredatthesamerateusingidenticalsizedstirbars.
Stir thoroughly and continuously.
• Calibrationstandardsandsamplesolutionsshouldbe
atthesametemperature.Thermallyinsulatesolution
vesselfrommagneticstirrerwithcorkorotherinsulat-
ing medium.
•Wait until sensor value has stabilized before taking
reading (at least 5 minutes when going from more
dilutetomoreconcentratedsamples,longerwhenthe
orderisreversed).
•SurfacecoatingonthePTFEmembranewilleffectthe
response. Inspectsensorbeforeusing.Washoffwitha
jet of deionized water or mild detergent to remove
film.
•Replace PTFE membrane if damage is evident or a
dropletofinternalelectrolyteisseen.
•Rinse electrode with distilled or deionized water be-
tweensamplesanddabdrywithlabwipeorothersoft
disposable absorbent toweling.
•Checkcalibrationevery1-2hours.Recalibrateifnec-
essary.
•Position sensorsatanangleofapproximately20°to
30°fromverticletoreducepossibilityoftrappinggas
bubbleson on the membranecap. Gas bubbles also
form from solution out-gassing due to temperature
change. Gentlytapbodyofsensortodislodgethem.
•ClosecontainerwithplasticwraporuseHI4000-71
gassensortestvesseltopreventgasfromleaving.
•Ifelectrodewasleftoutinairforaprolongedperiod,
gently pulling cable will permit an exchange of fill
solution at the membrane surface. Re-Calibration is
required.

8
VIII.VIII.
VIII.VIII.
VIII. Inner Electrode CheckInner Electrode Check
Inner Electrode CheckInner Electrode Check
Inner Electrode Check
Prior to assembling the electrode for the first timefirst time
first timefirst time
first time or
subsquently reactivating it after extended periods of dry
storage, the inner electrode assembly should be hydrated
andthentestedasapHelectrode.
PreparepHtestsolutions HI4000-47-4andHI4000-47-
7bymixinganddissolvingeachbufferpacketinseparate
containerswith50mLdeionizedwater.ThesepHsolutions
containchlorideionsandpHbuffersthatareusedtoverify
the inner electrode (pH internal) is operational. See
SectionXVIIforreplacementaccessoriesandmaintenance
items.
Foranewsensor:
Remove the protective shipping cap from the glass inner
electrode.
Forexistingsensor:
Unscrew the upper cap on the top of the electrode and
carefullywithdrawtheinternalpH/referenceassembly.
Usetest
tubeor
graduated
cylinder
(weighed
Bottom)when
testingor
conditioning
pHinternal
Testbuffer
canbe
usedasa
conditioning
solution
forthe
pHinternal
Protectiveshippingcap
Forstablereadings,glassshouldbecoveredto the
bottomofthelongblack band.

9
•Ifsensorhasbeenstoredorshippeddry,itshouldbe
“conditioned”by soaking the pH/reference assem-
bly1hourormoreinoneofthepHtestsolutions.
•Avoidtouching thepHglasswithyourfingers.
•Attention:ThepH/referenceassemblyisfragile!
Support the upper portion of the internal cell while
immersing the glass and reference assembly. A tall
narrowcontainerwithweighted bottom is best.The
pHtestsolutionshouldcoverthebottomofthelarge
black band.
Test:ConnecttheBNCconnectorontheelectrodecable toa
pH/mV(mVorORPmode)meter.Carefullyimmerse
thesensorassemblyintooneofthebuffers.Whenthe
measurmentstabilizesrecordthemVgenerated.Rinse
sensor tip in deionized water and dab dry between
bufferstopreventsolutioncarry-over.Donotrubthe
glass.Takeameasurementinthesecondbufferand
recordmV. Payattentiontominussignifpresent.
CalculatethedifferenceinmVbetweenthetwosolutions.
Example of typical values:
HI4000-47-7 -90.2mV
HI4000-47-4 80.66mV
Difference 170.8mV=80.6-(-90.2)
A calculated value equal or greater than 160 mV is ac-
ceptableforambienttemperaturesbetween20°and25°C.

10
3.) Using dropper provided, add about 2 mL of carbon
dioxide internal fill solution HI 4005-40 into outer
probebody.
IX.IX.
IX.IX.
IX. Electrode PreparationElectrode Preparation
Electrode PreparationElectrode Preparation
Electrode Preparation
1) Removeglassinternalfromsensorbodyandperform
innerelectrodecheck.(SeesectionVIII).
2) TheHI4105sensorcomeswiththreeeasilyreplace-
ablemembranecaps(twowhicharespares).Remove
a cap from membrane box and screw on to lower
threadsofouterprobebody,compressingtheo-ring
seal. Avoidtouchingworkingareaofmembranewith
your fingers as skin oil will change the membrane
properties.