7
You can prepare your own buffer solutions using the following recipes:
pH 4.00
Add 2.0 mL of 0.1 M HCl to 1000 mL of 0.1 M potassium
hydrogen phthalate.
pH 7.00
Add 582 mL of 0.1 M NaOH to 1000 mL of 0.1 M
potassium dihydrogen phosphate.
pH 10.00
Add 214 mL of 0.1 M NaOH to 1000 mL of 0.05 M sodium
bicarbonate.
Maintenance and Storage
Short-term storage (up to 24 hours): Place the electrode in pH 4 or pH 7 buffer
solution.
Long-term storage (more than 24 hours): Store the electrode in a pH 4 buffer/KCl
storage solution in the storage bottle. The electrode is shipped in this solution.
Vernier sells 500 mL bottles of pH Storage Solution (order code PH-SS), or you can
prepare additional storage solution by adding 10 g of solid potassium chloride (KCl)
to 100 mL of pH 4 buffer solution. Flinn Scientific (800-452-1261) sells a Buffer
Solution Preservative (order code B0175) that can be added to this storage solution.
By storing the electrode in this solution, the reference portion of the electrode is kept
moist. Keeping the reference junction moist contributes to electrode longevity and
retains electrode response time when the unit is placed back into service. If the
electrode is inadvertently stored dry, immerse the unit in pH 4 buffer/KCl storage
solution for a minimum of eight hours prior to service.
When testing a Go Wireless pH, it is best to measure a buffer solution because it is
easier to determine if the sensor is reading correctly. Do not test your sensor by
measuring distilled water. Distilled water can have a pH reading in the range of 5.5–
7.0, due to varying amounts of dissolved carbon dioxide. Furthermore, due to a lack
of ions, the pH values reported with the sensor in distilled water will be erratic.
If your Go Wireless pH is reading differently from the pH of a buffer solution (e.g.,
reads 6.7 in a buffer 7), you may simply need to calibrate.
If your readings are off by several pH values, the pH readings do not change when
moved from one buffer solution to another different buffer, the sensor was stored
dry, or the sensor’s response seems slow, the problem may be more serious. A
method called “shocking” can be used to revive pH electrodes. To shock your Go
Wireless pH, perform the following:
1. Soak the pH Electrode for 4–8 hours in an HCl solution of 0.1 M–0.5 M.
2. Rinse off the electrode and soak the tip in pH 7 buffer for 30–60 minutes.
3. Rinse the electrode and test it with buffer solutions of known pH.
Occasionally, mold will grow in the pH 4 buffer/storage solution. Mold will not
harm the electrode and can easily be removed using a mild detergent solution. Mold
growth in the storage solution can be inhibited by adding a buffer preservative.
The Go Wireless pH is designed to be used in aqueous solutions. The polycarbonate
body of the sensor can be damaged by many organic solvents. In addition, do not use
the sensor in solutions containing perchlorates, silver ions, sulfide ions, biological
8
samples with high concentrations of proteins, or Tris buffered solutions.† Do not use
the sensor with hydrofluoric acid or in acid or base solutions with a concentration
greater than 1.0 molar.
The electrode may be used to measure the pH of sodium hydroxide solutions with a
concentration near 1.0 molar, but it should not be left in this concentration of sodium
hydroxide for periods longer than 5 minutes. Using or storing the electrode at very
high temperatures (>80°C) or very low temperatures (near 0°C) can damage it
beyond repair.
Battery Information
Go Wireless Electrode Amplifier contains a small lithium-ion battery in the handle.
The system is designed to consume very little power and not put heavy demands on
the battery. Although the battery is warranted for one year, the expected battery life
should be several years. Replacement batteries are available from Vernier (order
code: GW-BAT-100).
Use only the Vernier Go Wireless Charging Cable (order code: GW-CB) or
Go Wireless Charging Station (order code: GW-CRG) to charge the battery.
Storage and Maintenance of Go Wireless Electrode Amplifier
To store Go Wireless Electrode Amplifier for extended periods of time, put the
device in sleep mode by holding the button down for at least three seconds. The red
LED will stop flashing to show that the unit is in sleep mode. Over several months,
the battery will discharge but not be damaged. After such storage, charge the device
for a few hours and the unit will be ready to go.
Exposing the battery to temperatures over 35
C (95
F) will reduce its lifespan. If
possible, store Go Wireless Electrode Amplifier in an area that is not exposed to
temperature extremes.
Replacement Parts
Vernier Software & Technology
Part
Order
code
Go Wireless Charging Cable
GW-CB
Go Wireless pH (electrode only)
GW-PH-NP
Go Wireless Battery
GW-BAT-100
Related Products
Go Wireless Charging Station (order code: GW-CRG)
Multi-sensor charging capability for your Go Wireless Electrode Amplifiers. The
Go Wireless Charging Station is the perfect solution for charging and storing your
Go Wireless Electrode Amplifier. For more information, see
www.vernier.com/gw-crg
†
Vernier offers a Tris-Compatible Flat pH Electrode that features a double junction electrode,
so it can be used with proteins, sulfides, and Tris buffers. It works with the Go Wireless
Electrode Amplifier. Order code FPH-BNC.
