WPI ISO-H2S-2 User manual

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WORLD
PRECISION
INSTRUMENTS
ISO-H2S-2
Hydrogen Sulde Sensor for use with WPI Analyzers
Serial No._____________________
www.wpiinc.com
INSTRUCTION MANUAL
030316

MACRO SENSORS
SPECIES Carbon
Monoxide Nitric Oxide Hydrogen Peroxide Oxygen Hydrogen Sulde
Order Number ISO-COP-2 ISO-NOP ISO-HPO-2 ISO-OXY-2 ISO-H2S-2
Available Diameters 2 mm 2 mm 2 mm 2 mm 2 mm
Response Time < 10 sec < 5 sec < 5 sec < 10 sec < 5 sec
Detection Limit/Range 10nM to 10µM 1 NM to 40µM* < 100nM to
100µM
0.1%-100% < 5nM-100µM
Sensitivity ~0.5 pA/nM ≤ 2 pA/nM 8 pA/µM 0.3-0.6nA/% 2 pA/nM
Drift <1pA/min <1pA/min 0.1pA/min < 1%/min
Temperature Dependent Yes Yes Yes Yes Yes
Physiological Interference nitric oxide NaNO2(10-6 or
better)
None None None
Replacement Sleeves (pkg
of 4)
#95620 #5436 #600012 #5378 #600016
Filling Solution #95611 #7325 #100042 #7326 #100084
Start-up Kit #95699 #5435 #600011 #5377 #600015
*Higher detection limit available on request — call for custom pricing.
• Real-time detection using electrochemical microsensors
• Measure nitric oxide from < 0.3 nM to 100µM.
• Measure hydrogen peroxide < 10 nM to 100mM
• Measure hydrogen sulde
• Measure glucose
• Measure oxygen from 0.1% to 100%
• Integrated system includes one temperature
sensor, your choice of two additional sensors,
and a start-up kit
• Current measurement range from 300 fA to 10
µA (four ranges) permits wide dynamic range for
detection.
• Wide bandwidth allows recording of fast events
• Isolated architecture allows Lab-Trax interface to simultaneously measure free
radical and independent analog data (i.e., ECG, BP, etc.) data on any channel.
Free Radical Analyzer
Other WPI Favorites

ISO-H2S-2
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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
Notes and Warnings................................................................................................................. 1
Parts List...................................................................................................................................... 2
Unpacking................................................................................................................................... 2
INSTRUMENT DESCRIPTION ........................................................................................................ 2
OPERATING INSTRUCTIONS......................................................................................................... 3
Polarizing the Sensor ............................................................................................................... 3
Calibrating the Sensor ............................................................................................................. 4
Preparing Na2S Stock Solution......................................................................................... 4
Calibration Procedure........................................................................................................ 4
MAINTENANCE ................................................................................................................................ 7
Durability and Handling........................................................................................................... 7
Cleaning the Membrane.......................................................................................................... 7
Replacing the Membrane Sleeve .......................................................................................... 8
ACCESSORIES................................................................................................................................... 9
TROUBLESHOOTING ...................................................................................................................10
SPECIFICATIONS............................................................................................................................11
INDEX...............................................................................................................................................13
DECLARATION OF CONFORMITY ..............................................................................................14
WARRANTY .....................................................................................................................................15
Claims and Returns ................................................................................................................15
Repairs.......................................................................................................................................15

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ISO-H2S-2
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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 ISO-H2S-2 sensor works with WPI free radical analyzers to monitor hydrogen
sulde.
INTRODUCTION
The basic structure of the ISO-H2S-2 sensor is shown in Fig. 2. It consists of an
internal H2S-sensing working/reference electrode combination. This electrode ts
inside a disposable protective stainless steel sleeve (WPI #600016) which must contain
fresh electrolyte (WPI #100084) and is separated from the external environment by a
gas-permeable polymeric membrane covering the end of the sleeve. The other end of
the sleeve is anged. The locking cap is used to attach the sleeve to the probe handle.
Notes and Warnings
NOTE: The sensor must be polarized for at least 12 hours in 0.1M PBS solution prior
to use.
NOTE: The sensor membrane and membrane coating are extremely delicate.
Improper handling will lead to damage of the sensor.
NOTE: For optimal use of each sensor and sensor membrane sleeve, the sensor must
be stored properly. See “Maintenance” on page 7. Pay special attention to the
sticker on the box. It says, “ THE SENSOR SLEEVE IS FILLED WITH ELECTROLYTE. IF THE
SENSOR IS NOT TO BE USED WITHIN ONE WEEK, REMOVE THE SLEEVE, CLEAN THE
SENSOR WITH DEIONIZED WATER, AND STORE THE SENSOR DRY.”

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Parts List
After unpacking, verify that there is no visible damage to the sensor. Verify that all
items are included:
(1) ISO-H2S-2 H2S sensor
(1) Probe Unpacking Instructions (Read this before handling the probe.)
(1) Spare membrane sleeve
(1) 1 cc Syringe
(1) MF28G67 MicroFil
(1) 100084 10mL vial of lling solution
(1) Instruction Manual
(1) Sensor Performance Evaluation
Unpacking
Upon receipt of this sensor, 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 15 of this manual. Please contact WPI Customer Service if any
parts are missing at 941.371.1003 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 15 of
this manual.
INSTRUMENT DESCRIPTION
combination
working / counter
electrode
probe
handle
stainless steel
sleeve
gas permeable
membrane
connection
to meter
locking cap
Fig. 2—The locking cap slides over the sensor sleeve. The sleeve is lled with electrolyte
and slides over the ISO-H2S-2 electrodes. The locking cap securely attaches the sleeve to
the sensor handle.

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Gas permeable membrane–The membrane covers the end of the stainless sleeve
to separate it from the external environment.
Stainless steel sleeve (WPI#600016, pkg. of 4)–The sleeve houses the sensitive
electrode pair. The sleeve is anged to properly connect with the locking cap. It must
contain fresh lling solution (WPI#100084).
Working/Counter electrode–This is an internal H2S-sensing pair of working and
counter (reference) electrodes.
Locking cap–This cap attaches the sleeve to the probe handle.
When the sensor is 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 cannot be
reused if the sleeve is removed from the electrode.
Additional membrane sleeves are available in packages of 4 (WPI #600016). The ISO-
H2S start-up kit (WPI #600015) also includes replacement membrane sleeves, along
with all the accessories to ll them properly with electrolyte solution.
OPERATING INSTRUCTIONS
Polarizing the Sensor
1. Place the sensor in 0.1M PBS solution
2. Plug it into the free radical analyzer.
3. Turn on the free radical analyzer.
4. Set the poise voltage on the free radical analyzer. On the TBR4100/1025, set the
Probe Select switch to H2S(150mV).
5. Plug in the ISO-H2S-2 sensor and allow it to polarize up to 12 hours to reach a
stable baseline current of <75000pA before it is used for measurement.
6. During initial polarization the current is typically high, but within an hour it will be-
gin to decrease rapidly. In order to observe this phenomenon, start by setting the
range to 100nA. After several hours the current will fall. The range should always
be set to 100nA, regardless of how low the baseline falls.
7. If the stabilized baseline value exceeds 75000pA, see “Replacing the Membrane
Sleeve” on page 8.
NOTE: This polarization procedure assumes the temperature is 25ºC. At 37ºC the
baseline current is higher.

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Calibrating the Sensor
Preparing Na2S Stock Solution
1. Use a 100mL volumetric ask. Dissolve 5mg EDTA in 100mL distilled water.
2 Purge the solution vigorously with argon gas for 15 minutes.
3. Weigh 24.0mg of sodium sulde (Na2S .9 H2O) (reagent plus, 99.99+% from Sigma)
and dissolve it in the solution under argon atmospheres.
4. Seal the ask with a rubber stopper. The solution is 1.0mM Na2S. Store the solu-
tion in a dark bottle and refrigerate at 2–8°C.
Calibration Procedure
The sensor should be immersed in PBS and plugged into the free radical analyzer. Set
the range to 100nA and the poise to H2S (150mV). Once the sensor is polarized, It can
be calibrated. The following example describes the fundamental concepts behind a
standard calibration protocol. Known concentrations of H2S are generated in PBS by
adding a known volume of a the Na2S stock solution.
1. Place a 20mL vial of PBS on the magnetic stirring plate with the small stir bar still
inside. Turn on the stirrer so that the bar is stirring at a moderate rate.
NOTE: This rate of the stirrer should NOT be modied during calibration.
NOTE: The calibration should be carried out at the same temperature at which
the experimental measurements are to be made. This can be accomplished by
placing the vial and stand in a water bath at the appropriate temperature and
allowing the temperature of the solution in the vial to equilibrate with the water
bath.
2. Immerse the ISO-H2S-2 sensor in the solution and secure it in an electrode
holder such as WPI’s Pro-Guide (WPI #47510, 47520, 47530, 47540) or a micro-
manipulator. The sensor tip should be immersed about 2–3mm into the solution.
It should not contact the stir bar, which could damage the membrane.
3. Connect the H2S sensor into a channel of a free radical analyzer. Set the poise
voltage to +150mV. For the Apollo 4000, this is accomplished in the software.
Use the custom option to manually set the voltage to 150mV. For the Apollo
1000 select poise from the main menu and set it to “internal”. Then, adjust the
poise voltage using a small screwdriver to turn the “poise adjust” potentiometer
on the front panel. For the TBR4100, simply set the “probe select” control on the
front panel to H2S. Allow the sensor to polarize for 12 hours.
The quiescent baseline current is an indicator of the health of the sensor. A cor-
rectly operating sensor has a baseline current of < 75,000pA.
4. To the vial containing 20mL PBS, sequentially inject three aliquots of Na2S solution
(20µL, 40µL and 80µL). The current output increases after each addition and then
plateaus. As soon as it reaches a plateau, inject the next aliquot.

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The reaction produces H2S gas. When H2S gas passes through the gas permeable
membrane, it generates an output current that is measurable, and the results can
then be graphed. This corresponds to 1µM, 2µM and 4µM nal concentrations,
respectively.
The output from the TBR4100/1025 looks similar to the example shown in Fig. 3.
Here three sequential additions of H2S were made to the PBS.
6. Calculate the concentration of H2S in solution after the each aliquot injection of to
20mL of PBS. The concentration of H2S produced can be calculated as follows:
M1V1= M2V2 where M=molarity and V=volume
1st Aliquot: 20µL + 20mL = 20,020µL
1000µM(20µL) = M2(20,020µL)
20,000µM/20,020 = 0.999µM = 999nM
2nd Aliquot: 40µL + 20,020µL = 20,060µL
1000µM(40µL) = M2(20,060µL)
40,000µM/20,060 = 1.994µM = 1994nM
3rd Aliquot: 80µL + 20,060µL = 20,140µL
1000µM(80µL) = M2(20,140µL)
80,000µM/20,140 = 3.972µM = 3972nM
Fig. 3—The calibration curve shows that three aliquots were added.
7. Record the calculated concentration values and the resulting sensor currents in a
table similar to the one below. Record the dierence in current output (pA) gener-
ated by the addition of the known quantities of H2S in a table similar to the one
below.

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Amount added [H2S] nM Response (pA)
20µL 999 3986.76
40µL 1994 6717.67
80µL 3972 10077.81
8. Construct a standard calibration curve using the recorded data. Using a third
party spreadsheet with graphing capability like Microsoft®Excel, it is possible to
generate a linear regression analysis that will display the equation and the R2
coecient. To do this in Excel, enter the data and generate a “scatter plot” graph.
Then, select the line and right click. Choose Add Trendline. The Add Trendline
dialog box appears. On the Type tab, select Linear, and on the Options tab,
select the Display equation on chart and Display R-value on chart.
Fig. 4—Calibration Output
The slope of this curve indicates the sensitivity of the sensor. Once the sensitivity
of the probe has been determined, the sensor is ready to use experimentally. (In
the above example, the sensitivity was 1.98pA/nM.)
NOTE: Because the H2S sensor is sensitive to salinity and temperature, calibration
and subsequent measurements should be performed in solution with the same
temperature and salinity.
***The H2S sensor measures the dissolved H2S gas, which is only one component of
the total sulde equilibrium system. The total sulde concentration [S2] = [H2S] +
[HS–] + [S2
–], so the H2S concentration can be calculated by: [H2S] = [Na2S]/{ 1+ K1/
[H+] + K1K2/[H+]}
For K1and K2, ( pK1= 6.89, pK2=19) see
Frank J. Millero, Tinka Plese, Marino Fernandez(1988)
Limnology and Oceanography, 33(2): 269
Giggenbach, W. (1971). Inorg. Chem. 10:1333.
Meyer, B.; Ward, K.; Koshlap, K.; & Peter, L. (1983). Inorganic Chemistry 22:2345.
Myers, R. J. (1986). Journal of Chemical Education 63:687.