Ionode IJ-Ag2S Sulphide - Manual (Page 2)

Application
The Ionode IJ-Ag
2
S Ion selective electrode measures free
sulphide and silver ions (Ag + ) in aqueous solutions.
The limit of detection is 0.003 ppm (Sulfide), and 0.01 ppm
(Silver). The electrode can also be used for low level
cyanide and halide titrations.
Interfering Ions
Mercury ions should be absent.
Ions that complex with measured species.
Cleaning
If the membrane is poisoned by interferences, the surface
may be renewed by careful polishing with fine wet-and-
dry (P1200 grade). The membrane surface should have a
polished metallic appearance. Always inspect the membrane
before use, and clean if necessary. Organic contaminants
can be removed with ethanol. DO NOT use the electrode in
chlorinated hydrocarbons.Routinely remove the sleeve and
replace the potassium nitrate electrolyte.
Electrolyte Replacement
The electrode has an inbuilt double junction Ag/AgCl with
a replaceable sleeve electrolyte. 1M potassium nitrate is
suitable for most applications. Please consult Ionode Customer
Service if you wish to use a different sleeve electrolyte.
Calibration Standards
Standard solutions should preferably bracket the expected
measurement range. Sulphide standards are susceptible to
oxidation and are not commercially available; these are to be
made fresh and the titer determined by standardisation with
Lead Perchlorate or equivalent.
The need for ISA (Ionic Strength Adjuster)
It is important to use ISA, so that the Ionic Strength of
standards and samples is independent of the concentration of
the measured ion. It is also important for pH adjustment. Use
10M NaOH or SAOB (Sulphide Anti-Oxidant Buffer) for Sulphide
determination. Sodium nitrate or similar can normally be used
for silver and halide determination.
Calibration Procedure
Before use, the electrode should be calibrated by measuring
a series of known standard solutions by serial dilution of
stock standard. For sulphide measurement, each
decade of concentration will have a theoretical difference
of 29mV (@25C). Similarly, for silver determination, the
theoretical difference is 59mV. In practice, the measured
differences will be less than these values. Acceptable
values for slope are -56±4mV for Ag
+ and -28±4mV for S 2- .
Other measurement Techniques
An unknown concentration can be determined by adding
a small known amount of a concentrated standard to
a known volume of sample. Other incremental techniques
include sample addition, standard subtraction and
analyte subtraction. More details can be obtained from
the Theory Section at www.ionode.com
Titration of Chloride
The electrode may also be used as an indicator to follow
the progress of a chloride (or other halide) titration using
silver nitrate. During the titration, the added silver
reacts with the halide ions forming a silver halide
precipitate. At the stoichiometric end point, a large
potential change occurs as silver ions end up in excess.
These titrations may be performed manually or
automatically using an automatic titrator.
Introduction
This guide contains the basic information for proper use
of your new Silver/Sulphide Ion-selective electrode.
Preparation
IJ series electrodes are shipped without sleeve electrolyte,
and must be filled prior to use. To fill, hold the electrode
by the sleeve and gently ease off the rubber wetting cap.
Prepare as follows:
2. Fill the annular space with
electrolyte to approximately half
to three quarter full.
1M potassium nitrate is normally
recommended.
1. 2.
1. Invert the electrode. Hold the
electrode just below the sleeve
and with careful rotation and
pulling along the axis of the
electrode, remove the sleeve.
DO NOT BEND.
3. Slide the sleeve back onto the electrode ensuring the black O-
ring is well seated within the electrode body. Do not exert side-
ways force. Any excess electrolyte will be expelled from the end
of the electrode through the ground junction. Ensure there are no
air bubbles in the sleeve.Wash off any excess electrolyte before use.
3.
GOOD CHEMISTRY
GOOD CHEMISTRY
Typical sulphide
calibration curve
Typical silver
calibration curve