REDOX AND REFERENCE ELECTRODE USER MANUAL
Contents
1. Temperature C pH 4 buffer pH 7 buffer 20 470 295 25 462 285 30 454 275 Do the following 1 Connect the pH mV Meter to your computer and start your SensorTrace program If you use a strip chart recorder or other data acguisition device connect this to the output connections of the pH mV Meter 2 Prepare guinhydrone redox buffer solutions Mix 100 ml of pH 4 buffer solution with 1 g of quinhydrone Do the same with a pH 7 buffer solutions Crystals of quinhydrone should be present indicating that the solution is saturated 3 Expose both the reference electrode and the redox microelectrode tips to both quinhydrone redox buffers pH 4 and 7 With use of Unisense software do the following 4 Start SensorTrace BASIC or PRO with a new experiment choose the redox sensor Press START 5 The calibration tab is now shown Put the redox electrode and the reference electrode into the pH 4 buffer The signal is shown in signal In Value Redox pot mV you manually enter the correct value from the table above e g 470 at 20 C Press ADD POINT when the signal is stable look at the time series measurements 6 Now move the electrodes to the pH 7 buffer and do the same entering the value from the table above e g 295 at 20 C Press ADD POINT You now have the correct calibration 7 Press APPLY CALIBRATION and the calibration is shown in the table below the graph 82. at the end of measurements 3 Check the level of the filling solution It should be approximately 0 5 cm below the filling hole If necessary refill the KCI Ag 3M solution saturated with AgCl Unisense Reference electrode 1 When receiving a new electrode remove the shock absorbing grey plastic net 2 Remove the lower piece of tape and the rubber stopper in order to empty the tube of storage liquid This liquid can be saved for future storage 3 The tip of the Unisense reference electrode not the Ref RM should be kept immersed in water or an aqueous solution at all times but can tolerate up to 10 minutes of exposure to air WARNING Do not remove the seal and protective plastic tube before the following steps 1 4 are successfully completed CONNECTING THE ELECTRODES Connect the Unisense redox microelectrode to the amplifier Connect the reference electrode to the black box on the redox electrode cable banana plug connection Immerse the redox electrode still in its protective tube in a buffer 7 solution Place the tip of a reference electrode in the same solution A Unisense redox electrode with internal reference has to be submerged sufficiently 2 3 cm in the medium to cover the liquid junction during all measurements In the following we assume that you are using Unisense pH mV Meter If you are using another meter perform analogous steps with the mV meter in question CALIBRATION Th
3. team We will respond to your inquiry within one working day E mail sales unisense com Unisense A S Tueager 1 DK 8200 Aarhus N Denmark Tel 45 8944 9500 Fax 45 8944 9549 Further documentation and support is available at our website www unisense com 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 RECOMMENDED METERS FOR REDOX SENSORS One channel meter pH mV Meter Multi channel meters for pH redox Microsensor Multimeter OVERVIEW REDOX ELECTRODE IMPORTANT The Unisense redox microelectrode is a miniaturized platinum Unisense sensors electrode designed for research applications within physiology are neither biotechnology environmental sciences and related areas intended nor With tip diameters down to around 10 microns the Unisense approved for use on humans redox microelectrode allows measurements of redox potential with a very high spatial resolution The redox microelectrode can be used for measurements in salinities from 0 to full ocean strength MEASURING PRINCIPLE When the electrode tip is immersed in an aqueous solution and
4. unauthorized repair or modification of the product In no event will Unisense A S be liable for any direct indirect consequential or incidental damages including lost profits or for any claim by any third party arising out of the use the results of 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 for damages on laboratory instruments due to unintended field use or exposure to dust humidity or corrosive environments REPAIR OR ADJUSTMENT Sensors and electrodes cannot be repaired Equipment that is not covered by the warranty will if possible be repaired by Unisense A S with appropriate charges paid by the customer In case of return of equipment please contact us for return authorization For further information please see the document General Terms of Sale and Delivery of Unisense A S as well as the manuals for the respective products CONGRATULATIONS WITH YOUR NEW PRODUCT SUPPORT ORDERING AND CONTACT INFORMATION The Unisense Redox electrode is a miniaturized platinum electrode that facilitates reliable and fast measurements with a high spatial resolution designed for research applications If you wish to order additional products or if you encounter any problems and need scientific technical assistance please do not hesitate to contact our sales and support
5. NG Problem Possible cause Solution Problem Possible cause 1 Solution Possible cause 2 Solution Drift in the calibration potential values Contamination of the platinum surface Clean the electrode tip as described above Sensitivity of the redox microelectrode is low or the signal is unstable Contamination of the platinum surface Clean the electrode tip as described above The reference electrode is malfunctioning Repair or change the reference electrode If you encounter other problems and need scientific technical assistance please contact sales unisense com for on line support we will answer you within one workday 20 MANUAL FOR REF RM REF321 Reference Electrode Electrode de R f rence 103 mm R Radiometer 12 mm Filling hole Orifice de remplissage Filling solution Solution de remplissage Ag AgCl wire Fil de Ag AgCl Porous plug Poreux _ Protection cap filled with 3M Capuchon de protection rempli de KCI 3M analytical 21 22 e KS410 Thiourea Solution for porous plugs contaminated with sulphides or blocked by an AgCI precipitate Duration of treatment a few hours until the porous plug turns white e RENOVOeN Normal Cleaning Solution greasy or oily deposits The porous plug of the electrode can be cleaned using a fine abrasive paper Storage Between measurements leave the REF321 in KS110 3M KCI So
6. Then you tick the box Calibrated in the lower part of the window The electrode signals are now shown as calibrated values and the electrodes are ready for use If the sensor functions according to the above description carefully remove the seal and the protective plastic tube before making measurements 15 MEASUREMENTS MouNTING OF ELECTRODE Although the Unisense Redox microelectrode is made of glass the tip is flexible and can bend slightly around physical obstacles However large obstacles like stones or coarse lateral movements of the electrode when the tip is in contact with a solid substrate may cause the tip to break Also due to the small size of the microelectrode tip and to the steepness of redox gradients in many environments even a displacement of the electrode tip of few microns may change its immediate redox environment Therefore measurements should be performed only ina stabilized set up fixed free of moving or vibrating devices We recommend the Unisense lab stand LS18 and the Unisense micromanipulator MM 33 MM33 2 or MMS for laboratory use For in situ use we recommend our in situ stand 1519 and a micromanipulator ELECTRICAL NOISE The electrical current generated by the high impedance microelectrode is very small Although the Unisense redox microelectrodes are very resistant to electrical noise from the environment electrical fields may interfere with the electrode signal Therefore w
7. Vh UNISENSE REDOX AND REFERENCE ELECTRODE USER MANUAL ee REDOX AND REFERENCE ELECTRODE MANUAL Copyright 2012 Unisense A S Version October 2012 UNISENSE A S TABLE OF CONTENTS SUPPORT ORDERING AND CONTACT INFORMATION OVERVIEW ri REDOX ELECTRODE REFERENCE ELECTRODE GETTING STARTED en en MEASUREMENT an a aa a MOUNTING OF THE ELECTRODE ADVANCED REDOX STORAGE AND STORAGE CLEANING THE ELECTRODE REFERENCES eae TROUBLE SHOOTING ee MANUAL FOR REFERM WARRANTY AND LIABILITY NOTICE TO PURCHASER This product is for research use only Not for 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 ofthe products WARRANTY AND LIABILITY The Redox electrode is covered by a 90 days limited warranty Microsensors are a consumable Unisense will only replace dysfunctional sensors if they have been tested according with the instructions in the manual within 14 days of receipt of the sensor s The warranty does not include repair or replacement necessitated by accident neglect misuse
8. connected via a high impedance millivolt meter to a reference electrode figure 1 and 2 immersed in the same solution the Redox electrode tip will develop an electric potential relative to the reference electrode which reflects the tendency of the solution to release or take up electrons also called the Oxidation Reduction Potential ORP Thus the redox microelectrode must be used in combination with a reference electrode e g Unisense REF RM and connected to a high impedance millivolt meter REFERENCE ELECTRODE The Unisense reference electrode is a simple open ended Ag AgCl electrode with a gel stabilized electrolyte The reference electrode is used to establish a reference potential against the redox microelectrode For laboratory use Unisense provides a macro reference electrode from Radiometer Analytical please see separate manual in the back of this booklet Our micro sized reference electrodes are glass electrodes manufactured at Unisense For in situ use Unisense manufactures a pressure compensated macro electrode 11 GETTING STARTED UNPACKING A NEW REDOX ELECTRODE 1 When receiving a new microelectrode remove the shock absorbing grey plastic net UNPACKING A NEW REFERENCE ELECTRODE Radiometer Ref RM 1 Remove the protection cap from the electrode and any seals covering the filling hole 2 Before starting a measurement remove the clip which closes the electrode filling hole Remember to replace the clip
9. e recommend that unnecessary electrical mechanical equipment is switched off and electrode or wires are not touched during operation IMPORTANT Construction of the electrode with an internal reference involves the creation of aliquid junction approximately 3 cm from the electrode tip During measurements this liguid junction has to be submersed in the medium in order to complete the measurement circuit ADVANCED REDOX ELECTRODES Unisense can construct redox electrodes for customer reguested applications at additional costs The most freguently construction options are described at our web page under redox electrode specifications http www unisense com support rd spec html The options include for instance customer specified dimensions pressure tolerance internal reference and cable length If your specifications for a special redox electrode are not described at our web page please contact salesaunisense com for further options and prices 17 STORAGE AND MAINTENANCE STORAGE REDOX ELECTRODE Store the electrode in the protective plastic tube used for shipping The room in which the redox microelectrode is stored should be dry and not too hot 10 30 C REFERENCE ELECTRODE Store in the protective glass tube used for shipping For short term storage lt 10 min the electrodes can be stored in air For long term storage the electrode tip must be immersed in 1M KCI in the protective casing used for ship
10. e redox potential reduction potential of a sample is measured in mV V or Eh where 1 Eh 1 mV For all practical purposes is it impossible to measure the absolute potential and thus redox potentials are always given as a value relative to the standard hydrogen electrode SHE In practice the reference electrodes available do not have the same potential as the SHE Therefore before all redox measurements it is important to measure the offset of the reference electrode that one is using relative to the standard hydrogen electrode This is easily done with the recommended quinhydrone redox buffers and Unisense software Quinhydrone is a mixture of equal amounts molar basis of hydrochinone and quinone IMPORTANT As the redox microelectrode is sensitive to temperature it is necessary to perform calibration and subsequently measurements at the same temperature IMPORTANT As redox electrodes directly reflects the potential to be measured the calibration is linear and in principle only 1 point calibration is needed However 2 points should be measured to ascertain valid electrode function Response time is up to 10 seconds 13 The buffers have a defined redox potential relative to the SHE electrode and thus these buffers can be used to calibrate the Unisense redox electrode with use of another reference electrode than the SHE electrode compensating the measurements with an offset Redox potential of buffers
11. hole If necessary refill with KCleAg 3 M KCI Solution saturated with AgCl If desired the concentration of KCI can be changed However it is advisable to use a high concentration Remember always to saturate the solution with AgCl For nonaqueous applications such as measurements in acetic acid Empty the electrode and fill it up again with a saturated KCI solution in acetic acid Saturate the solution with AgCl 4 In order to remove air bubbles trapped inside the electrode shake the electrode holding it at its head with the porous plug down Maintenance 1 Electrode contamination is a major cause of faulty measurements 2 The electrode should be rinsed with distilled water after measurements 3 Check frequently the level of filling solution 4 In case of deposits which cover the electrode clean the electrode with e a solution of acid 0 1M 0 1M HNO mineral salt deposits etc e KS400 Pepsin in HCI Solution or RENOVOeX Xtra Strong Cleaning Solution protein deposits milk cheese serums Duration of treatment 1 to 2 hrs 23 UNISENSE UNISENSE DENMARK www unisense com info unisense com
12. lution Overnight or longer seal the filling hole with paraffin film or with the electrode clip and fit back in place the protection cap filled with the KS110 3M KCI Solution Accessories KS110 3M KCI Solution 500 mi C20C320 KCleAg 3M KCI Solution S21M004 saturated with AgCI 100 ml ORENOVO N S16M001 Normal Cleaning Solution 250 CRENOVO X S16M002 Xtra Strong Cleaning Solution 250 ml KS400 Pepsin in HCI Solution 250 mi C20C370 KS410 Thiourea Solution 250 ml C20C380 CL111 Electrode cable with banana plug A94L111 Specifications Reference potential when filled with 3M KCI in mV Temperature C 0 10 20 25 30 40 vs std hydrogen elec 225 219 212 208 204 196 vs sat Hg Hg CI elec 35 36 36 36 37 38 Temperature range O to 80 C Note an electrode chain comprising pHG301 or XG100 200 glass electrode and a REF321 filled with 3M KCI will give a zero pH of approx pH 7 25 REF321 Reference Electrode Introduction The REF321 is a general purpose Ag AgCl reference electrode fitted with a screw cap Preparation for measurement 1 Remove the protection cap from the electrode and any seals covering the filling hole 2 Before starting a measurement remove the clip which closes the electrode filling hole Remember to replace the clip at the end of measurements 3 Check the level of the filling solution It should be approximately 0 5 cm below the filling
13. ping The room in which the electrodes are stored should be dry and not too hot 10 25 C MICRO REFERENCE ELECTRODE Store in the protective glass tube used for shipping For short term storage lt 10 min the electrodes can be stored in air For long term storage the electrode tip must be immersed in 1M KCI inthe protective casing used for shipping The room in which the electrodes are stored should be dry and not too hot 10 25 C CLEANING THE ELECTRODE The redox electrode can by cleaned by immersing it in nitric acid 1 1 H O Keep the electrode in the nitric acid solution for about 30 minutes and allow it to cool and rinse with water afterwards The Ref RM electrode should be rinsed with distilled water after measurements Check the level of filling solution often In case of deposits please consult the separate manual in the back of this manual The micro reference electrodes can be cleaned by flushing or submergence in 70 ethanol for a couple of minutes After this rinse with 1M REFERENCES K hl M Revsbech N P 2001 Biogeochemical microsensors for boundary layer studies In The Benthic boundary layer Boubreau B P Jorgensen B B eds New York Oxford University Press pp 180 210 lt Revsbech N P and B B Jorgensen 1986 Micro electrodes Their Use in Microbial Ecology p 293 352 In C Marshall Advances in Microbial Ecology vol 9 Plenum New York 19 TROUBLE SHOOTI
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