WPI ISO2 User manual

Instrumenting scientific ideas
WORLD
PRECISION
INSTRUMENTS
ISO2
Isolated dissolved oxygen meter and oxygen electrode
Serial No._____________________
www.wpiinc.com
INSTRUCTION MANUAL
030416

ISO2
World Precision Instruments i
Copyright © 2016 by World Precision Instruments, Inc. All rights reserved. No part of this publication
may be reproduced or translated into any language, in any form, without prior written permission of
World Precision Instruments, Inc.
CONTENTS
ABOUT THIS MANUAL ................................................................................................................... 1
INTRODUCTION .............................................................................................................................. 1
Parts List...................................................................................................................................... 2
Unpacking................................................................................................................................... 2
INSTRUMENT DESCRIPTION ........................................................................................................ 3
Sensor Structure and Assembly............................................................................................ 3
Recorder Output....................................................................................................................... 3
OPERATING INSTRUCTIONS......................................................................................................... 4
Calibration................................................................................................................................... 4
Polarization ........................................................................................................................... 4
Zero (Oxygen) Point Calibration....................................................................................... 5
Scale Factor Adjustment.................................................................................................... 6
Calibration for O2in Living Tissue/Blood............................................................................. 8
MAINTENANCE ................................................................................................................................ 9
Durability and Handling........................................................................................................... 9
Storing the Sensor.................................................................................................................... 9
Cleaning the Membrane........................................................................................................10
Sterilizing the Membrane......................................................................................................10
Replacing the Membrane Sleeve ........................................................................................10
Cleaning the Electrode Surface ...........................................................................................12
Batteries ....................................................................................................................................12
ACCESSORIES.................................................................................................................................12
TROUBLESHOOTING ...................................................................................................................13
Dry Sensor Test .......................................................................................................................13
APPENDIX .......................................................................................................................................15
DECLARATION OF CONFORMITY
...........................................................................................................................................................18
WARRANTY .....................................................................................................................................19
Claims and Returns ................................................................................................................19
Repairs.......................................................................................................................................19

ii World Precision Instruments

ISO2
World Precision Instruments 1
ABOUT THIS MANUAL
The following symbols are used in this guide:
This symbol indicates a CAUTION. Cautions warn against actions that can cause
damage to equipment. Please read these carefully.
This symbol indicates a WARNING. Warnings alert you to actions that can cause
personal injury or pose a physical threat. Please read these carefully.
NOTES and TIPS contain helpful information.
Fig. 1—The ISO2meter works with the OXELP oxygen sensor.
IMPORTANT NOTE: Before using the ISO2 dissolved oxygen meter for the rst time,
connect the sensor and apply power to the instrument overnight.
IMPORTANT NOTE: The OXELP oxygen sensor is specically designed to be used
with WPI’s ISO2dissolved oxygen meter. To use the OXELP with other instruments,
see Fig. 2 on page 3 for plug information.
INTRODUCTION
ISO2and its associated OXELP sensor provide accurate, stable and electrically isolated
oxygen measurements. The recorder output is not electrically connected to the
OXELP sensor circuitry. This oers the important advantage that other sensors may
be used in the same sample as the OXELP without interfering with one another, and
background noise is greatly reduced. With a sensor tip diameter of just 2mm and low
oxygen consumption, ISO2and its associated sensor excel in making measurements

2 World Precision Instruments
in small sample volumes. Other features include a fast response time and a sturdy
stainless steel sensor body.
The instrument amperometrically measures the concentration of oxygen in aqueous
solutions and gas mixtures. Measurements can be displayed either as a percentage of
atmospheric pressure, parts per million (ppm), or as a redox current in nanoamperes
(nA). The oxygen sensor houses a platinum working electrode and a silver counter/
reference sensor inside a stainless steel sleeve. A gas permeable polymer membrane
ts over the end of the sleeve which allows oxygen to pass while blocking liquids, ions
and particulate matter. Oxygen diuses through the membrane and is reduced at the
platinum cathode which is held at –0.7V when the instrument is on. This results in an
electrical current being generated, the magnitude of which is determined by the rate of
diusion to the sensor which is proportional to the partial pressure of oxygen outside
the membrane. The current serves as a measure of the partial pressure of oxygen.
ISO2comes ready to use. Just attach the OXELP sensor to the meter, turn the power
on and wait for the current to decay to a stable value. This usually takes a couple of
hours. The current can be monitored by setting the ISO2to the nA setting. Once the
current stabilizes you may then calibrate the instrument.
Parts List
After unpacking, verify that there is no visible damage to the sensor. Verify that all
items are included:
(1) 5377 OXELP Startup kit, including:
(2) 2mm OXELP sleeves
(1) 3563 1CC syringe without needle
(1) 5379 Filler bottle
(1) 7326 Bottle of lling solution, 10mL
(1) MF28G67 Microl, 28 gauge
(1) ISO2 Dissolved oxygen meter
(1) OXELP Oxygen electrode probe
(1) Instruction Manual
Unpacking
Upon receipt of this instrument, make a thorough inspection of the contents and
check for possible damage. Missing cartons or obvious damage to cartons should be
noted on the delivery receipt before signing. Concealed damage should be reported
at once to the carrier and an inspection requested. Please read the section entitled
“Claims and Returns” on page 19 of this manual. Please contact WPI Customer
Service if any parts are missing at 941-301-1003 or [email protected].
Returns: Do not return any goods to WPI without obtaining prior approval (RMA
# required) and instructions from WPI’s Returns Department. Goods returned
(unauthorized) by collect freight may be refused. If a return shipment is necessary,
use the original container, if possible. If the original container is not available, use a
suitable substitute that is rigid and of adequate size. Wrap the instrument in paper or
plastic surrounded with at least 100mm (four inches) of shock absorbing material. For
further details, please read the section entitled “Claims and Returns” on page 19 of
this manual.

ISO2
World Precision Instruments 3
INSTRUMENT DESCRIPTION
Sensor Structure and Assembly
The basic structure of the OXELP sensor is shown below (Fig. 2).
Male BNC
Connector
Membrane Sleeve
Electrodes
Locking Cap
Probe Handle
Fig. 2—OXELP Sensor assembly
Membrane–Gas permeable, polymeric membrane covering the end of the stainless
sleeve to separate it from the external environment
Sleeve–Disposable, protective stainless steel sleeve (WPI#5378) that houses the
sensitive electrode pair. The sleeve is anged to properly connect with the locking
cap. It must contain fresh electrolyte (WPI#7326).
Electrode–Internal O2-sensing pair of working and counter (reference) electrodes
Probe Handle
Locking Cap–Attaches the sleeve to the probe handle
When the sensor is fully assembled (with locking cap and sleeve in place) the internal
electrode should press gently against the polymeric membrane, which will be slightly
stretched. This ensures that the electrolyte diusion is as thin as possible, minimizing
sensor response time.
NOTE: Once a membrane is stretched it is permanently
deformed and should not be reused if the sleeve is removed
from the electrode.
Additional membrane sleeves are available in packages of 4
with electrolyte lling solution (WPI #5378). The start-up kit
(WPI #5377) also includes replacement membrane sleeves,
along with all the accessories to ll them properly with
electrolyte solution.
Fig. 3—(Right) The 5377 ISO2startup kit includes a calibration
bottle, lling solution, syringe, MicroFil and two membrane sleeves.
Recorder Output
The recorder output terminal is electrically isolated. This oers an important recording
advantage because other sensors in the same test medium will not interact adversely
with OXELP. The output signal from the Recorder connector is 1mV/nA of sensor
current regardless of whether the selector switch is in the %, ppm or nA range.

4 World Precision Instruments
OPERATING INSTRUCTIONS
Calibration
For accurate results the sensor should be calibrated as closely as possible to the
temperature and medium at which the measurement is to be made (if measurements
are in gas, calibrate in gas).
To calibrate the sensor:
1. Turn on the ISO2, and polarize the sensor (“Polarization” on page 4).
2. Zero the sensor (“Zero (Oxygen) Point Calibration” on page 5).
3. Adjust the scale factor (“Scale Factor Adjustment” on page 6).
NOTE: The O2solubility ppm tables are located in the Appendix.
NOTE: With an external data recorder, a three-point calibration can be used. Refer to
the ISO-OXY-2/OXELP manual available from www.wpiinc.com/manuals.
Polarization
The OXELP sensor should always remain connected to the ISO2. When the ISO2is
turned o a potential of –0.2V is applied to the platinum working electrode. This is
done to minimize the time required for the current to decay when the instrument is
turned on and a potential of –0.7V is applied to the working electrode.
The ISO2meter will keep the OXELP sensor polarized if it is left connected to the
meter, even when the meter is switched o. For best results, polarization of a new
sensor should be performed over a 24-hour period. However, a 2-hour period will
polarize the sensor enough for 95% accuracy.
TIP: You can determine whether or not the correct potential is being applied to the
working electrode when the instrument is on by placing the instrument in the Vw
setting. The LCD display shows the potential being applied. If the potential is not –0.7V,
then change the potential to the correct value by using a small screw driver to adjust
the Vw ADJ screw on the front panel of the instrument.
To polarize the sensor:
1. Place the sensor in 0.1M PBS solution or water.
2. Connect the sensor to the ISO2. Position the BNC connector, push it into place
and turn the locking nut clockwise to securely connect it.
3. Turn on the ISO2and switch the meter to the nA mode.
4. The sensor current initially will be high, but it will fall and settle to a stable value
usually after about two hours. The sensor should be allowed at least one hour to
reach a stable baseline current of 16–80nA before it is used for measurement.
Once the current stabilizes, calibrate the instrument.
5. If the stabilized baseline value exceeds 80nA, see “Replacing the Membrane
Sleeve” on page 10.
NOTE: This polarization procedure assumes the temperature is 25ºC. At 37ºC the
baseline current is higher.

ISO2
World Precision Instruments 5
Zero (Oxygen) Point Calibration
The true electronic zero reading can be obtained by removing the sensor from the
ISO2 meter. At that point, the meter has no current running through it and is at the
electronic zero. The meter should read zero. As soon as you connect the sensor to the
meter, you can have a small current leakage, called the baseline current. We calibrate
an instrument to correct for the baseline current. To ensure that the sensor is
registering only the baseline current, ALL oxygen must be purged from the calibration
medium.
There are several methods for calibrating the sensor:
• In liquid (water or PBS) bubbled with N2gas to
purge any intrinsically dissolved O2
• In liquid saturated with sodium hydrosulde
(Na-Dithionite Na2SO4) to inhibit any intrinsically
dissolved O2
• In a pure N2gas environment
Choose the calibration method that most closely
approximates the conditions of the experiment to be
run. For example, if you are measuring oxygen in a PBS
solution, use the liquid calibration method.
Fig. 4—(Right) The calibration bottle is included with the ISO2system.
Liquid Calibration
The OXELP sensor is designed for measurement of oxygen in liquids. For short
periods of time, it can be used in a gas environment. If the sensor will be used in a gas
environment, use the gas calibration method (page 6).
1. Polarize the sensor. See “Polarization” on page 4. Leave the polarized sensor
immersed in PBS and plugged into the ISO2meter until you are ready to calibrate it.
2. Fill the supplied plastic calibration bottle (Fig. 4) about 2/3full of distilled water.
Screw the bottle cap on the bottle.
TIP: If your experiment uses PBS solution, use PBS to calibrate the sensor and
purge the oxygen by bubbling nitrogen in the mixture (Step 3).
3. To purge the oxygen from the liquid, connect 1/8˝ ID plastic tubing (not supplied)
to the port on the side of the bottle. Connect the other end of the tubing to a
pure nitrogen gas source at a low pressure (less than 5 PSI). Bubble nitrogen into
the calibration medium for at least 10 minutes.
TIP: If you prefer, you may use an oxygen scavenger like Na2S2O4(Sigma-Aldrich
#157953) or Na2SO3(Sigma-Aldrich #71988) to inhibit the oxygen action in
the distilled water. Be aware that temperature and salinity changes aect the
concentration of the solute needed to purge the oxygen. Solubility tables can be
found in the “Appendix” on page 15. Be sure to use enough of your oxygen
scavenger to completely eliminate the oxygen in the bottle for the duration of the
calibration procedure.
Sensor
Bottle Cap
/8
˝ Tubing
1

6 World Precision Instruments
CAUTION: Wear nitrile gloves when handling sodium sulte (Na2SO3).
4. Carefully slide the tip of the OXELP sensor through the hole in the top of the
bottle cap. Position the sensor so that the probe handle rests against the bottle
cap. If the bottle is top heavy, you may need to support the sensor. The current
should drop rapidly (after a few seconds) to a value of 0nA.
5. If the current value is not zero, use the Zero ADJ knob to get a zero reading. Use
this procedure to obtain a zero reading on any scale setting (nA, ppm, %). Do not
rotate the zero adjust knob after the zero calibration is complete.
NOTE: If you move the sensor to a liquid that has a change in salinity, it may take a
few minutes for the sensor current to re-stabilize.
Gas Calibration
The OXELP sensor is not designed for long-term use in a gas environment, but may
be used for short experiments.
1. Polarize the sensor. See “Polarization” on page 4. Leave the polarized sensor
immersed in PBS and plugged into the ISO2meter until you are ready to calibrate it.
2. Screw the bottle cap on the plastic calibration bottle. Connect 1/8˝ ID plastic
tubing (not supplied) to the port on the side of the bottle. Connect the other end
of the tubing to a pure nitrogen gas source at a low pressure (less than 5 PSI). Fill
the supplied plastic calibration bottle with pure nitrogen gas for 10 minutes.
3. Carefully slide the tip of the OXELP sensor through the hole in the top of the
bottle cap. Position the sensor so that the probe handle rests against the bottle
cap. If the bottle is top heavy, you may need to support the sensor. The current
should drop rapidly (after a few seconds) to a value of 0nA.
4. If the current value is not zero, use the Zero ADJ knob to get a zero reading. Use
this procedure to obtain a zero reading on any scale setting (nA, ppm, %). Do not
rotate the zero adjust knob after the zero calibration is complete.
Scale Factor Adjustment
After the instrument has been zeroed, you must adjust the scale factor according
to whether or not the intended measurements are to be made in the gas phase or
aqueous medium.
Gas Phase Measurements
Sensor calibration for gas phase measurements can be accomplished using the
calibration bottle, as described above for zeroing the instrument with nitrogen.
Further calibration can be performed using a tank of known oxygen concentration (for
example, 100% O2or carbogen–95% O2).
1. Turn the Select knob to %.
2. When the bottle is purged with nitrogen as described in “Gas Calibration” on page
6, the display should read 0.
3. Use the same method to purge the bottle with a known concentration of oxygen.