STERILIZABLE DISSOLVED OXYGEN SENSORS
Contents
1. AppliSens SENSOR INNOVATION 4 100 81802. 675 mV The oxygen molecules that diffuse through the semi permeable membrane and the thin layer of electrolyte are reduced at the cathode while the silver anode is oxidized simultaneously Polarization causes a current to flow which is measured by the amplifier this current is proportional to the partial pressure of oxygen in the medium The slope of the O sensor is temperature pressure and medium dependent Therefore calibration must be performed under operating conditions Same temperature pressure and medium To enable automatic temperature correction the standard version sensor with the AppliSens logo on the connector is fitted with an integrated NTC resistor k 4 R 22 kOhm 25 C B25 50 3560 OPERATION The sensor comes with a protective cap to avoid mechanical damage of the sensor tip and prevent evaporation of the electrolyte this cap must be removed before using the sensor AppliSens sterilizable dO sensors are supplied factory tested and certified with membrane module in place When the system is operated for the first time or when the sensor has been disconnected from the controller for longer than 5 minutes the sensor must be polarized connected to the dO amplifier for at least 6 hours prior to calibration If the sensor is only disconnected for a couple of minutes less than 6 hours will be sufficient Insufficient polarization will cause an increased ch AppliSens SENSOR INNOVATION
3. ELECTROLYTE AND MEMBRANE WARNING The O electrolyte is strongly alkaline pH 13 Contact of electrolyte with skin especially mucous membrane or eyes must be avoided use safety glasses and gloves If such contact occurs the affected area must be thoroughly rinsed with water Get medical attention if adverse symptoms appear When the membrane starts to shows signs of failure refer to section 6 Maintenance it must be replaced When replacing the membrane module and electrolyte strictly follow the instructions below Hold the sensor in a vertical position membrane downwards and unscrew the old membrane module Rinse the interior electrode body and the annular space between this and the lower part of the steel shaft with d i water and dry it carefully with a lint free tissue Visually inspect the O ring for mechanical defects and replace if necessary Hold the membrane module with a tissue and fill it with 1 mi 40 drops of electrolyte ELECTRODE SHAFT MEMBRANE MODULE 4 100 8180 APPLISENS STERILIZABLE DISSOLVED OXYGEN SENSORS Note When this instruction is not followed carefully the membrane in the module may be damaged Hold the electrode vertically and screw the membrane module very slowly onto the shaft After refreshing electrolyte for the ADI dO sensor the sensor has to be repolarized see paragraph 2 After replacing the membrane module the sensor has
4. residual signal and therefore lead to measurement errors see section 4 Electrode Verification Note In case of autoclavable systems the electrode cable must be removed before sterilization cover the electrode connector with a cap or cotton with Sterilizable aluminum foil CALIBRATION If the measurement is performed under sterile conditions the system should be calibrated after sterilization since sterilization may alter the sensor slope After cooling the fermentor must be aerated long enough to reach a constant oxygen pressure the signal is allowed to stabilize and the reading of the amplifier adjusted to the desired value e g 100 air saturation 20 9 oxygen saturation or e g 9 17 mg O l pure water at 20 C and 760 mmHg Note In case of autoclavable systems the sensor must be connected to the amplifier immediately after sterilization in order to polarize it it is recommended to polarize the electrode for at least several 6 hours before calibration Preferably calibration should take place just before inoculation the longer the polarization period the higher the measuring accuracy Homogenize the medium by stirring during calibration in order to prevent a diffusion gradient A one point calibration is normally enough to enable accurate measurements over the full range between O and 100 dO at 0 dO the polarized sensor system does not generate any current However it is good practice to
5. verify the measured signal at 0 dO Strip all oxygen from the medium by pure N gas 99 98 and follow the reading of the sensor until it is stabilized In case the final reading is gt 0 5 of air saturation the sensor needs maintenance refer to section 10 The sensor should be pre sterilized once before calibrating in order to prevent measurement errors After the first sterilization new membrane modules may show a slope alteration of some percent of the measuring signal after a second sterilization only a fraction of the first alteration will be observed 4 100 8180 4 APPLISENS STERILIZABLE DISSOLVED OXYGEN SENSORS ELECTRODE VERIFICATION It is good practice to verify the sensor before it is put to use An elevated residual signal signal at 0 oxygen saturation indicates malfunctioning of the O sensor If the reading at 0 dO is too high gt 0 5 of air saturation the sensor should be inspected see section 10 Trouble Shooting Verify the sensor by placing it in an oxygen free environment either in pure N gas or in a solution from which all oxygen was stripped with N 99 98 Note Do not use CO gas for stripping oxygen from the calibration verification solutions since this will introduce an error After 5 to 10 minutes the reading should be stable In case the bioreactor is sparged with N take enough time to strip all oxygen from the solution MOUNTING When mounting the sensor in the reacto
6. 100200010 Cable pH DO 2p sensor L 2 0m BNC T a U Low drift In Situ sterilizable dO sensor with detachable cable and titanium gi module DN25 port application l Z010011020 Sensor Dissolved Oxygen L 110 12mm 2P for Z101002510 DN25 pH DO Sensor Holder or for Ml Z100002520 Sensor holder DN25 A Tracfix Z010015420 Sensor Dissolved Oxygen L 154 12mm 2P for Z100002530 Sensor holder DN25 B Tractfix F Z100380010 Cable pH DO 2P sensor L 3 8m BNC E Z100500010 Cable pH DO 2P sensor L 5 0m BNC U Accessories and spare parts Z110000410 Membrane kit Dissolved Oxygen sensor 4 modules electrolyte 50ml 4 O rings Z110000420 Membrane kit Dissolved Oxygen sensor titanium 4 modules electrolyte 50ml 4 O rings Z110005010 Electrolyte Dissolved Oxygen sensor 50ml lt AppliSens SENSOR INNOVATION 4 100 8180 APPLISENS STERILIZABLE DISSOLVED OXYGEN SENSORS 10 TROUBLE SHOOTING PHENOMENON Zz REASON VERIFICATION WHAT TO DO 1 Slope out of range Short circuit in cable Check reading with connected cable but Replace cable if reading more Slope gt 0 6 at 37 C without sensor than 0 5 of air saturation ai C Ground loop Earthing potential difference between Earth fermentor and fermentor head plate and measuring measuring device at the same device controller earth point Pa Damaged membrane Visually inspect the membrane Replace membrane module 2 No sensitivity a No polarization voltage Amplifier Verify polarisation voltag
7. a current voltage curve Rinse thoroughly ae Sensor not polarized long Polarization lt 6 hours Polarize more than 6 hours enough Check reading with detached module and _ If reading more than 0 5 of carefully dried inner body air saturation the sensor is defective Check reading with detached module and _ If reading more than 0 5 of carefully dried inner body air saturation the sensor is defective lt AppliSens SENSOR INNOVATION 4 100 8180 APPLISENS STERILIZABLE DISSOLVED OXYGEN SENSORS PHENOMENON REASON VERIFICATION WHAT TO DO 5 Unexpected high reading during O free and CO saturated CO interference of dO sensor measurement medium Interference of air O bubbles May be observed with air lift reactors or in Place sensor in a region with cultures of high cell density less air O bubbles c Elevated pressure in the E g caused by an increased flow Avoid increased pressure bioreactor resistance in sterile filter Membrane fouled Layer on membrane Clean with soft tissue or replace module Damaged membrane Visually inspect the membrane Replace membrane module Contaminated cathode Not visible can only be identified by Clean with tooth paste recording a current voltage curve Rinse thoroughly Very viscous medium Sluggish response is normal in case of a viscous medium 6 Sluggish response 7 Unstable signal Air O bubbles sticking on May be observed with air lift reactors or in Change stirring and or membra
8. e Bi Cable rupture Verify resistance of cable Replace cable C Not enough electrolyte in Visual inspection Electrolyte must contact Refresh electrolyte solution membrane module anode S Membrane completely fouled Impermeable layer on membrane Clean membrane module or replace it ee e Malfunction in sensor Sensor Replace sensor 3 Sensitivity too low Depleted electrolyte After long term measurements of more Replace electrolyte solution Slope lt 0 3 at 37 C than 6 months Contaminated anode Black silver ring brown is o k Clean with tooth paste caused by S Rinse thoroughly Contaminated cathode Not visible can only be identified 4 Clean with tooth paste recording a current voltage curve Rinse thoroughly Membrane fouled Layer on membrane Clean with soft tissue or replace module 4 Elevated residual signal Short circuit in cable Check reading with connected cable but Replace cable if reading more Verify with O free medium without sensor than 0 5 of air saturation E SS C Ground loop Earthing potential difference between Earth fermentor and fermentor head plate and measuring measuring device at the same device controller point Pe Damaged membrane Visually inspect the membrane Replace membrane module Test with CO gas instead of N The dO sensor shows a CO Use N or Bisulphite solution interference in absence of O catalysed by Co IlI salt f Contaminated cathode Not visible can only be identified ou Clean with tooth paste recording
9. ne cultures of high cell density aeration conditions or change probe location Damaged membrane Visually inspect the membrane Replace membrane module Crack in glass body at the Visual inspection Unstable signal If crack in glass body sensor cathode especially at low pO is defective Electrostatic interference Apply equipment according to certified conditions After sterilization In Situ Time between cooling down and Increase cooling interval systems only calibration too short Membrane fouled Layer on membrane Clean with soft tissue or replace membrane module C Damaged membrane Visually inspect the membrane Replace membrane module Contaminated cathode Not visible can only be identified by Clean with tooth paste recording a current voltage curve Rinse thoroughly Contaminated anode Black silver ring brown is o k e g Clean with tooth paste caused by S Rinse thoroughly Ground loop Earthing potential difference between Earth fermentor and fermentor head plate and measuring measuring devices at the device controller same point Change of pressure in E g caused by an increase of the flow Avoid changes in pressure bioreactor resistance in sterile filter Change of medium temperature Verify medium temperature Avoid changes in temperature Too much electrolyte in the Add only 1 ml 40 drops of module electrolyte and screw the module very slowly onto the shaft O 8 Drift too large f gt 9 Membrane torn lt
10. p APPLISENS STERILIZABLE DISSOLVED OXYGEN SENSORS STERILIZABLE DISSOLVED OXYGEN SENSORS USER MANUAL Table of Contents SOMIDNAWNE Introduction Operation Calibration Electrode Verification Mounting Maintenance Storage Instructions for Exchange of Electrolyte and Membrane Ordering Information Trouble Shooting L 7 AppliSens SENSOR INNOVATION 4 100 8180 APPLISENS STERILIZABLE DISSOLVED OXYGEN SENSORS 1 INTRODUCTION The ADI dO sensors are used for measuring the partial pressure of dissolved oxygen in media for biotechnological processes The sensors are available in two versions a standard version with a stainless steel membrane tip and a low drift version with a titanium membrane tip Both types of dO sensors are available in different sizes for application in the head plate of a 2 20 liter autoclavable bioreactor and in the bottom DN25 insert of the 20 200 liter Bio Bench Pilot In Situ reactors Control of dissolved oxygen tension can be obtained in combination with the ADI 1030 autoclavable systems or the ADI 1060 in situ systems Bio Controller The polarographic ADI dO sensor is based on the principle of a Clark cell It consists of a platinum working electrode cathode and a silver counter reference electrode anode the gas permeable membrane separates the electrode from the medium The polarographic amplifier supplies a constant polarization voltage of
11. r head plate or bottom insert be careful not to damage it both the membrane and inner body are fragile Note The low drift type has a PG 13 5 thread that can be mounted into the DN25 port sensor holder for pH and DO electrodes for In Situ applications MAINTENANCE Visually inspect the membrane for damage prior to each calibration If the membrane is contaminated clean it with a moist soft cloth Depending on the nature of the medium the electrolyte may have to be changed periodically it must be refreshed at least every six months Note If the medium contains components that diffuse through the membrane like acetic acid aldehyde or neutral mercaptanes the electrolyte must be refreshed more frequently The membrane module must be replaced when it starts to show elevated residual signal sluggish response drifting or noisy readings mechanical damage etc see section 10 Trouble Shooting ch y AppliSens SENSOR INNOVATION 7 STORAGE Filled with electrolyte for the ADI dO sensor the electrode can be stored for several months provided that the protective cap is covering the membrane module to prevent evaporation of the electrolyte During this period of time the electrode can be kept polarized so it is always ready for use For storage over longer periods the sensor should be stored dry e g in the membrane module without electrolyte INSTRUCTIONS FOR EXCHANGE OF
12. to be sterilized calibrated see paragraph 3 and verified see paragraph MEMBRANE MODULE 4 9 ORDERING INFORMATION Normal autoclavable dO sensor in different lengths detachable cable head plate application ih Z010023510 Sensor Dissolved Oxygen L 235MM 1 5L 12mm Z010038510 Sensor Dissolved Oxygen L 385MM 7 15L 12mm Z010059010 Sensor Dissolved Oxygen L 590MM 20L 2 12mm Z110200010 Cable D Oxygen sensor L 2 0m BNC Z110200020 Cable DO sensor NTC L 2 0m leads Normal In Situ sterilizable dO sensor with detachable cable DN25 port application Z010007010 Sensor Dissolved Oxygen L 70mm DN 25 Z110380010 Cable D Oxygen sensor L 3 8m BNC Z110500010 Cable D Oxygen sensor L 5 0m BNC Z110500020 Cable DO sensor NTC L 5 0m leads et 1 Low drift autoclavable dO sensor in different lengths detachable cable and titanium i module head plate application Z010006521 Sensor Dissolved Oxygen L 65 12mm 2P fixed PG13 5 for 250L BioSep aT Z010023520 Sensor Dissolved Oxygen L 235 1 5L 12mm 2P Z010038520 Sensor Dissolved Oxygen L 385 7 15L a 12mm 2P Z010059020 Sensor Dissolved Oxygen L 590 20L 2 12mm 2P wan Z
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