®
Model No. PS-2230
pH/ISE/ORP
5
012-14325A
pH/ISE/ORP
The pH/ISE/ORP input of the multi-sensor is a specialized voltage sensor. Its BNC
connector accepts the included pH electrode, as well as ISE and ORP electrodes (not
included). The sensor measures the voltage produced by any of these electrodes.
When used with a pH probe, the sensor also computes the pH based on the measured
voltage.
Connect the pH electrode (or other electrode) to the pH/ISE/ORP port and start data
collection. On your computer or interface, display the
ISE Voltage
measurement (this
measurement is valid for pH and ORP electrodes as well as ISE) or the
pH
measure-
ment for the calculated pH (assuming that the pH electrode is connected).
Measuring pH
The pH electrode produces a voltage proportional to the pH of the solution that it is
immersed in. This voltage is measured by the multi-sensor, which computes pH.
Unscrew and remove the storage bottle from the electrode (be careful not to spill the
storage solution). Push the O-ring and bottle cap up the electrode handle. Rinse the
electrode tip with distilled water. If you see bubbles in the electrode bulb, gently
shake the electrode downward (similar to shaking down a thermometer). Start data
collection. Place the tip of the electrode in the solution to be measured and wait for
the reading on your computer or interface to stabilize. Rinse the electrode with dis-
tilled water before measuring another solution.
pH Calibration
The pH measurement can be calibrated; however, for most applications calibration is
not necessary. Perform a two-point calibration with two buffer solutions of known
pH. Refer to the SPARKvue/SPARK SLS, Capstone, or Xplorer GLX User’s Guide or
Online Help for calibration instructions.
pH Electrode Maintenance and Storage
Cleaning
If the pH electrode becomes contaminated, use one of these methods to clean and
restore it. After any of these procedures, soak the electrode in a pH 7 buffer solution
for 30 minutes.
•
General Contamination:
Soak the electrode in 0.1 molar hydrochloric acid
(HCl) for 15 minutes.
•
Protein Deposits:
Soak the electrode in a solution of 1% pepsin in 0.1 molar
HCl.
•
Inorganic Deposits:
Rinse the electrode with 0.1 molar ethylene diamine
tetra-acetic acid (EDTA) tetrasodium solution.
•
Oil and Grease Film:
Wash the electrode carefully in a mild detergent or a sol-
vent known to be effective for the particular film.
•
Unknown Contamination:
Soak the electrode alternately in 12 molar sodium
hydroxide (NaOH) and 1 molar HCl. Leave it in each solution for one minute.
Rinse completely between soakings. End with HCl. (The NaOH etches the glass
and the HCl reestablishes hydrogen ions on the surface.)
