pH and Ref Sensor Manual

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pH AND REFERENCE ELECTRODE USER MANUAL


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pH AND REFERENCE ELECTRODE MANUAL

UNISENSE A/S

pH andreferenceelectrodemanual

Copyright 2012 Unisense A/S

Version October 2012


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TABLE OF CONTENTS

p H A ND REFE REN CE ELECTR OD E U SER MA NUA L 3

WARRANTY AND LIABILITY 8

CONG RAT UL AT IONS WI TH YOUR NE W PR OD UCT! 9

Support, ordering, andcontactinformation 9

OVERVIEW 11pH electrode 11

referenceelectrode 11

GETTING STARTED 12

unpackinganewpH electrode 12

unpackinganewreferenceelectrode 12

connectingtHeelectrodeS 13

calibration 13

MEASUREMENTS 14mountingoftHeelectrode 14

ADVANCED PH ELECTRODES 15

STORAGE AND MAINTENANCE 16Storage 16

cleaningtHeelectrode 16

REFERENCES 17

TROUBL E SHOOTI NG 18

MANUAL FOR REF-RM 20


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Support, ordering, andcontactinformation

This microelectrode is a miniaturized conventional pH electrode

based on selective diusion o protons through pH glass The small

tip size acilitates rapid and precise pH measurements in a broad

variaty o micro environments

I you wish to order additional products or i you encounter any

problems and need scientiic/technical assistance, please do not

hesitate to contact our sales and support team We will respond to

your inquiry within one working day

Email: sales@unisensecom

Unisense A/S

Tueager 1

DK8200 Aarhus N, Denmark

Tel: +45 8944 9500

Fax: +45 8944 9549

Further documentation and support is available at our website

wwwunisensecom

CONGRATULATIONS WITH YOUR NEW PRODUCT!

REPLACEMENT OF SENSORS

Unisense will replace sensors that have been damaged during shipment provided that:

The sensors were tested immediately upon receipt in accordance with the delivery note

and the manual

The seal is still intact.

The sensors are returned to Unisense for inspection within two weeks.

The sensors are correctly packed for return to Unisense, in accordance with the note

included in the sensor box.

noticeto purcHaSer

This product is or research use only Not or use in human diagnostic or

therapeutic procedures

warning

Microsensors have very pointed tips and must be handled with care to

avoid personal injury and only by trained personnel

Unisense A/S recommends users to attend instruction courses to ensure

proper use o the products

warrantyand liability

The pH electrode is covered by a 90 da ys limited warranty

Microsensors are a consumable Unisense will only replace dysunctional

sensors i they have been tested according with the instructions in the

manual within 14 days o receipt o the sensor(s)

The warranty does not include repair or replacement necessitated by

accident, neglect, misuse, unauthorized repair, or modiication o the

product In no event will Unisense A/S be liable or any direct, indirect,

consequential or incidental damages, including lost proits, or or any

claim by any third party, arising out o the use, the results o use, or the

inability to use this product

Unisense mechanical and electronic laboratory instruments must

only be used under normal laboratory conditions in a dry and clean

environment Unisense assumes no liability or damages on laboratory

instruments due to unintended ield use or exposure to dust, humidity

or corrosive environments

repairor adjuStment

Sensors and electrodes cannot be repaired Equipment that is not

covered by the warranty will, i possible, be repaired by Unisense A/S

with appropriate charges paid by the customer In case o return o

equipment please contact us or return authorization

For urther inormation please see the document General Terms o Sale

and Delivery o Unisense A/S as well as the manuals or the respective

products

WARRANTY AND LIABILITY


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OVERVIEW

This manual covers all Unisense pH and reerence electrodes

pH electrode

The Unisense pH micro electrode is a miniaturized glass pH

electrode designed or research applications within physiology,

biotechnology, environmental sciences, and related areas

With tip diameters down to 10 microns, the Unisense pH micro

electrode allows measurements o pH with a very high spatial

resolution The Unisense pH micro electrode can be used ormeasurements in salinities rom zero to ull ocean strength

meaSurementprinciple

The electric potential relects the acidity o the solution Thus

the pH micro electrode must be used in combination with a

reerence electrode (internal or external) and connected to a

highimpedance (>1014 Ohm) millivoltmeter When the electrode

tip is immersed in an aqueous solution and connected via a

millivoltmeter to a reerence electrode immersed in the same

solution, the pH electrode tip will develop an electric potential

relative to the reerence electrode, relecting the pH o the

solution

referenceelectrode

The Unisense reerence electrode is a simple openended AgAgCl

electrode with a gelstabilized electrolyte The reerence electrodeis used to establish a reerence potential against the pH micro

electrode

For laboratory use, Unisense provides a macro reerence electrode

rom Radiometer Analytical (please see separate manual in the

back o this booklet)

Our microsized reerence electrodes are glass electrodes

manuactured at Unisense

For in situ use, Unisense manuactures a pressurecompensated

macro electrode

WARNING

Unisense sensors

are neither

intended nor

approved for use

on humans

RECOMMENDED METERS FOR PH SENSORS

One-channel meter: pH/mV-Meter

Multi-channel meters for pH: Microsensor Multimeter


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connectingtHeelectrodeS

Connect the Unisense pH micro electrode to the ampliier

Connect the reerence electrode to the black box on the pH

electrode cable (banana plug connection)

Immerse the pH electrode (still in its protective tube) in a buer

7 solution Place the tip o a reerence electrode in the same

solution

A Unisense pH electrode with internal reerence has to be

submerged suiciently (23 cm) in the medium to cover the liquid

junction during all measurements

In the ollowing, we assume that you are using Unisense pH/

mVMeter I you are using another meter, perorm analogous

steps with the mVmeter in question Also, please see note in the

margin o this page

calibration

Please consult the sotware manual or instruction on how to

calibrate in the sotware

Connect the pH/mVMeter to your computer and start your

SensorTrace program I you are using a strip chart recorder

or other data acquisition device, connect this to the output

connections o the pH/mVMeter Expose both the reerence

electrode and pH micro electrode tip to at least three dierent

pH buers covering the range in which measurements are to be

made Record the signal size in your sotware or e ach pH buer

The pH micro electrode should respond linearly between

these points with a slope of 50-70 mV/pH-unit. Millivoltreadings during subsequent measurements can be converted to

pH values with a linear conversion using the calibration values

This can be done directly in the SensorTrace sotware (please see

the sotware manual or instructions)

If the sensor functions according to the above description, carefully remove the

black tape with the white seal and the protective plastic tube before making

measurements.

IMPORTANT

As the pH micro

electrode is

sensitive to

temperature, it

is necessary to

perform calibration

and measurements

at the same

temperature.

NOTE

Conventional

pH-meters

often have an

automated

calibration

procedure.

However, due to

the very small area

of pH-sensitive

glass on the

electrodes, this

does not work

well. Therefore Do

NOT use the auto

calibration, but

read the signal in

mV and convert it

to pH afterwards.

unpackinganewpH electrode

1 When receiving a new micro electrode, remove the

shockabsorbing grey plastic net

2 Remove the lower piece o black tape and the rubber stopper

in order to empty the tube o storage liquid This liquid can be

saved or uture storage

3 Remove the clear tape covering the hole just below the screwThis will expose a small hole in the protection tube, and allow

the liquid to run out The sensor is now ready or calibration

NOTE: i you have a pHMR electrode, calibrate in the protective

tube and then careully move the sensor rom this tube into the

provided blue guide

unpackinganewreferenceelectrode

ref-rm

1 Remove the protection cap rom the electrode and any seals

covering the flling hole

2 Beore starting a measurement, remove the clip which closes

the electrode flling hole Remember to replace the clip at the

end o measurements

3 Check the level o the flling solution It should beapproximately 05 cm below the flling hole I necessary refll

the KClAg 3M KCl solution, saturated with AgCl

uniSenSe referenceelectrode

1 Follow 12 under pH electrode

2 The tip o the Unisense reerence electrode (not the ReRM

electrode) should be kept immersed in water or an aqueous

solution at all times, but can tolerate up to 10 minutes o

exposure to air

GETTING STARTED WARNINGDo not remove the

seal and protective

plastic tube before

the following steps

and calibration

are successfully

completed.

IMPORTANT

If you have apH-MR electrode,

calibrate in the

protective tube

and then carefully

move the sensor

from this tube into

the provided blue

guide.


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ADVANCED PH ELECTRODES

Unisense can construct pH electrodes or customer requested

applications at an additional cost Unisense provides several

options or customizations (eg tip size, response time, and

stirring sensitivity) and adaptations (eg mounting in needle or

lowthrough cell), making accurate measurements possible or

even more applications

Please visit our website or more inormation

mountingoftHeelectrode

To mount the electrode or measurements, unscrew the screw,

breaking the white paper seal When the screw is loose, the sensor

can be drawn rom the protective tube and used normally

Although the Unisense micro electrodes are made o glass, the

tip is lexible and can bend slightly around physical obstacles

However, large obstacles like stones or coarse lateral movements

o the electrode when the tip i s in contact with a solid substrate

may cause the tip to break

Also, due to the small size o the microsensor tip and to

the steepness o gradients in many environments, even a

displacement o the electrode tip o ew microns may change its

environment

Thereore measurements should be performed only in a

stabilized set-up fixed on a sturdy table free of moving or

vibrating devices. We recommend the Unisense lab stand LS18

and the Unisense micromanipulator MM33 (MM332 double) or

laboratory use For insitu use we recommend our in situ stand

(IS19) and a micromanipulator

electricalnoiSe

The electrical current generated by the highimpedance micro

electrode is very small Although the Unisense pH micro electrodes

are very resistant to electrical noise rom the environment,

electrical ields may interere with the electrode signal Thereore

we recommend that unnecessary electrical or mechanical

equipment is switched o and the electrode or wires are not

touched during operation

MEASUREMENTS

TEMPERATURE

Closely monitor

the temperature,

because the sensor

signal will vary

with temperature.


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REFERENCES

Khl, M, Revsbech, N P 2001

Biogeochemical microsensors or boundary

layer studies In: The Benthic boundary layer,

Boubreau, B P, Jrgensen, B B (eds) New

York, Oxord University Press pp 180210

Revsbech, N P, and B B Jrgensen 1986

Micro electrodes: Their Use in Microbial

Ecology, p 293352 In K C Marshall (ed),Advances in Microbial Ecology, vol 9

Plenum, New York

Thomas, RC 1978 Ionselective intracellular

microelectrodes; how to make them and use

them Academic Press, London

Storage

pH electrode

The pH electrode should be stored upright in the protective tube

Always keep the tip moist For longterm storage the electrode

tip can be immersed in demineralized water in the tube For

shortterm storage (


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TROUBLE SHOOTING

If you encounter other problems and need scientific/technical assistance, please contact

[email protected] for online support (we will answer you within one workday)

Solution Replace reerence electrode

Possible cause 6 Insoluble compounds deposited at the gel/water junction o the

micro reerence electrode

Solution Replace reerence electrode

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TROUBLE SHOOTING

Problem The sensitivity o the pH micro electrode is low, the signal is stable

and does not change with pH

Possible cause The pH sensitive tip has suered physical damage and is most

likely broken

Solution Replace the electrode

Problem Sensitivity o the pH micro electrode is low or the signal is

unstable

Possible cause 1 The pH meter is not suitable or pH micro electrodes

Solution Change the pH meter to one with a suiciently high impedance

(>1014 Ohm) (eg Unisense pH/mVMeter)

Possible cause 2 The reerence electrode is not properly connected or is

malunctioning

Solution Connect the reerence electrode and make sure that it is

properly submerged in the same solution as the pH electrode

Alternatively, repair or change the reerence electrode

Possible cause 3 Insoluble compounds have been deposited on the pH sensitive

tip

Solution Rinse the tip with ethanol, rinse with 001 M HCl and rinse with

distilled water

Possible cause 4 Air bubbles present at the tip o a micro reerence electrode

Solution Remove bubbles with a ine brush and avoid entrapment o

bubbles

Possible cause 5 Contamination o micro reerence halcell with soluble

compound eg sulide (visible dark band approaching the halcell

through the gel)


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MANUAL FOR REF-RM


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UNISENSE, DENMARK

wwwunisensecom ino@unisensecom

Documents

pH and Ref Sensor Manual