PASCO CI-6734 User Manual
Instruction Manual and
Experiment Guide for the
PASCO scientific
Model CI-6734
SODIUM ION SELECTIVE
ELECTRODE
012-06615A
9/97
© 1997 PASCO scientific $7.50
®
10101 Foothills Blvd. • P.O. Box 619011 • Roseville, CA 95678-9011 USA
Phone (916) 786-3800 • FAX (916) 786-8905 • web: www.pasco.com
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Sodium Ion Selective Electrode 012–06615A
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012–06615A Sodium Ion Selective Electrode
Table of Contents
Introduction......................................................................................................................................... 1
Theory .................................................................................................................................................. 1
Equipment ........................................................................................................................................... 2
Included ........................................................................................................................................ 2
Additional Required...................................................................................................................... 2
Required Solutions.............................................................................................................................. 2
General Preparation ........................................................................................................................... 4
Electrode Preparation.................................................................................................................... 4
Electrode Slope Check Using Science Workshop .......................................................................... 4
Measurement....................................................................................................................................... 5
Measuring Hints............................................................................................................................ 5
Sample Requirements ................................................................................................................... 5
Units of Measurement................................................................................................................... 5
Measurement Procedure .................................................................................................................... 6
Direct Measurement of Sodium ....................................................................................................6
Low Level Sodium Determination ............................................................................................... 7
Electrode Characteristics ................................................................................................................... 8
Reproducibility ............................................................................................................................. 8
Interferences.................................................................................................................................. 8
Temperature Influences................................................................................................................. 9
Electrode Response ..................................................................................................................... 10
Limits of Detection ..................................................................................................................... 10
pH Effects ................................................................................................................................... 10
Electrode Life ............................................................................................................................. 11
Maintenance .......................................................................................................................................11
Electrode Storage ........................................................................................................................ 11
Specifications..................................................................................................................................... 12
Troubleshooting Guide ..................................................................................................................... 12
Glassware/Plastic-ware ............................................................................................................... 12
Electrode ..................................................................................................................................... 12
Standards & Reagents ................................................................................................................. 13
Sample ........................................................................................................................................ 13
Technique .................................................................................................................................... 13
Troubleshooting Hints ...................................................................................................................... 13
Technical Support ............................................................................................................................. 17
i
Copyright, Warranty , and Equipment Return
PleaseFeel free to duplicate this manual
subject to the copyright restrictions below.
Copyright Notice
The PASCO scientific 012-06615 A manual is
copyrighted and all rights reserved. However,
permission is granted to non-profit educational
institutions for reproduction of any part of the Sodium
Ion Selective Electrode manual providing the
reproductions are used only for their laboratories and
are not sold for profit. Reproduction under any other
circumstances, without the written consent of PASCO
scientific, is prohibited.
Limited Warranty
PASCO scientific warrants the product to be free from
defects in materials and workmanship for a period of
one year from the date of shipment to the customer.
PASCO will repair or replace at its option any part of
the product which is deemed to be defective in
material or workmanship. The warranty does not
cover damage to the product caused by abuse or
improper use. Determination of whether a product
failure is the result of a manufacturing defect or
improper use by the customer shall be made solely by
PASCO scientific. Responsibility for the return of
equipment for warranty repair belongs to the
customer. Equipment must be properly packed to
prevent damage and shipped postage or freight
prepaid. (Damage caused by improper packing of the
equipment for return shipment will not be covered by
the warranty.) Shipping costs for returning the
equipment after repair will be paid by PASCO
scientific.
Credits
Author: Peter Boyle
Editor: Steve Miller
Equipment Return
Should the product have to be returned to PASCO
scientific for any reason, notify PASCO scientific by
letter, phone, or fax BEFORE returning the product.
Upon notification, the return authorization and
shipping instructions will be promptly issued.
ä
NOTE: NO EQUIPMENT WILL BE
ACCEPTED FOR RETURN WITHOUT AN
AUTHORIZATION FROM PASCO.
When returning equipment for repair, the units must
be packed properly. Carriers will not accept
responsibility for damage caused by improper
packing. To be certain the unit will not be damaged in
shipment, observe the following rules:
➀ The packing carton must be strong enough for the
item shipped.
➁ Make certain there are at least two inches of packing
material between any point on the apparatus and the
inside walls of the carton.
➂ Make certain that the packing material cannot shift in
the box or become compressed, allowing the
instrument come in contact with the packing carton.
Address: PASCO scientific
10101 Foothills Blvd.
P.O. Box 619011
Roseville, CA 95678-9011
Phone: (916) 786-3800
FAX: (916) 786-3292
email: techsupp@pasco.com
web: www.pasco.com
ii
012–06615A Sodium Ion Selective Electrode
E=E
S
X
E
X
X
γ
C
1
C
X
Introduction
The PASCO scientific Sodium Ion Selective Electrode is used to quickly, simply, accurately, and economically
measure sodium ions in aqueous solutions.
Theory
The Sodium Ion Selective Electrode is composed of a sodium-selective glass membrane bonded to a glass body.
When the membrane is in contact with a solution containing sodium ions, an electrode potential develops across
the membrane. This electrode potential is measured against a constant reference potential, using an ISE Amplifier
and a ScienceWorkshop computer interface. The level of sodium ions, corresponding to the measured potential, is
described by the Nernst equation.
log
+
0
where:
= measuredelectrodepotential
= referencepotential(a constant)
E
0
mV
S = electrodeslope( ≈ 59
decade
)
= level ofsodiumionsin solution
The activity, X, represents the effective concentration of free sodium ions in the solution. The activity is related to
the free ion concentration, C
, by the activity coefficient, γ by:
ƒ
=
ƒ
Activity coefficients may vary, depending on the total ionic strength, I, determined as:
I =
ΣCXZ
2
2
X
where:
= concentrationofion
X
ZX= charge of ion X
Σ = sum of all of the types of ions in the solution
In the case of high and constant ionic strength relative to the sensed ion concentration, the activity coefficient, γ is
constant and the activity, X, is directly proportional to the concentration.
1
Sodium Ion Selective Electrode 012–06615A
To adjust the background ionic strength to a high and constant value, ionic strength adjuster is added to samples
and standards. The recommended ISA for sodium is an ammonium chloride/ammonium hydroxide buffer.
Solutions other than this may be used as ionic strength adjusters as long as ions that they contain do not interfere
with the electrode’s response to sodium ions.
Equipment
Included:
to ISE
Amplifier
• Sodium Ion Selective
Electrode
• Sodium Ion Selective
Electrode fill solution
• pipette for fill solution
Sodium Ion Selective
Electrode
Additional Required:
Required Equipment
• PASCO CI-6738 ISE (Ion Selective Electrode) Amplifier
• Science Workshop 2.2.5 or higher
• PASCO Science Workshop Computer Interface
• Semilogarithmic 4-cycle graph paper for preparing
calibration curves.
• magnetic stir plate
• Lab-ware made of plastic, not glass, for all low level
measurements.
Required Solutions
The stock solutions described in this section may be created as
described in the text or ordered directly from PASCO. The solutions
available for order, and their respective prices are listed on the ‘ISE
Working Solution Price List’.
• Deionized or distilled water for solution and standard
preparation.
filling pipette
Figure 1.
Included Equipment
2
R
O
R
O
1
e
f
e
r
0
1
3
S
e
n
c
e
Fi
l
l
4
M
K
E
L
P
M
A
n
tio
u
l
o
S
I
C
filling
solution
• Ionic Strength Adjuster (ISA), 4 M NH
Cl/4 M NH4 OH
4
To prepare this solution, half fill a 1000 ml volumetric flask
with distilled water and add 214 grams of reagent-grade
ammonium chloride (NH
concentrated ammonium hydroxide (NH
Cl). Under a hood, add 270 ml of
4
OH), swirl the
4
flask gently to dissolve the solid, and allow to cool. Fill the
flask to the mark with distilled water, cap, and upend
several times to mix the solution.
• Sodium Electrode Storage Solution, 5 M NaCl
To prepare this solution, add 29.2 grams of reagent-grade
sodium chloride (NaCl) to 100 ml of distilled water. To
each 100 ml storage solution, add 2 ml of ISA.
012–06615A Sodium Ion Selective Electrode
ä
Note: Electrodes must not be stored in distilled water or air. Do not rinse with
distilled water.
• Dilute Electrode Rinse Solution
To prepare this solution from your own laboratory stock, add 20 ml of ISA to a one liter volumetric flask
and fill to the mark with distilled water. Use this solution to rinse the electrode between measurements.
• Sodium Standard, 0.1 M NaCl
To prepare this solution, half fill a one liter volumetric flask with distilled water and add 5.84 grams of
reagent-grade NaCl. Swirl the flask gently to dissolve the solid. Fill the flask to the mark with distilled water,
cap, and upend several times to mix the solution.
• Sodium Standard, 1,000 ppm Na
+
To prepare this solution, half fill a one liter volumetric flask with distilled water and add 2.542 grams of
reagent grade NaCl. Swirl the flask gently to dissolve the solid. Fill the flask to the mark with distilled water,
cap, and upend several times to mix the solution.
• Sodium Standard, 100 ppm Na
+
To prepare this solution, half fill a one liter volumetric flask with distilled water and add 0.254 grams of
reagent grade NaCl. Swirl the flask to dissolve the solid. Fill the flask to the mark with distilled water, cap,
and upend several times to mix the solution.
3
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