Bellingen Riverwatch Online Water Quality Monitoring Manual
Part 2. Can be done at the river or at home / school

2.2.2. pH - using pH Meter (for Never Never sites)

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Important Are you on the correct page?!

These instructions are only for the two kits that test the Never Never river.

See Lesson 2.2.1 for the pH instructions for most kits.

Equipment

  • Bottle of tap water

  • 500ml water sample

  • LAQUA-Twin pH11/pH22 Meter

  • Latex gloves

  • pH 4.01 buffer solution

  • pH 7.00 buffer solution

  • Paper towel

  • Pipette

  • Safety glasses

  • Tissues

Important

Should I use distilled water or tap water?

The advice from our supplier, Vendart Diagnostics, since making the videos is that, if it is for storage (as in to keep the probe moist or wet for periods of inactivity), then tap water is best. However, if it is for cleaning purposes in between tests, then distilled water is best, due to is neutrality and lack of compounds which could lead to contamination.

Part 1 : Electrode Conditioning (complete the day before testing).

(see video above)

1. Clean the sensor with distilled water.

2. Dry the sensor with a paper towel

3. Place some drops of the pH buffer 7 standard solution on the flat sensor. Cover the flat sensor.

4. Keep the meter flat. Close the lid.

5. Leave it overnight.

6. The next day, wash sensor with distilled water.

7. Dab dry with paper towel.

Part 2 : Calibration (complete at home, on the morning of testing).

1. Keep cover closed. Press the ON button on the meter until ‘P 11’ appears on the screen.

2. Open the light shield cover. Rinse the sensor with water and remove moisture on the sensor and meter by dabbing gently with a soft tissue. The flat sensor is made of thin glass, do not wipe or push the flat sensor.

3. Place the meter on a flat surface.

5. Place several drops of the pH buffer 7 on the flat sensor taking care to cover the entire sensor unit. Give the sensor a little jiggle to help spread the buffer solution (look closely and see that the two circular shapes within the flat sensor are covered).

4. Keep the light shield cover open and rinse the sensor with a small amount of pH 7 buffer to reduce sample crossover contamination. Gently blot dry.

6. Close the light shield cover and press the CAL button until a black box with CAL written in it and a smiley face starts blinking on the screen.

7. When the calibration is complete the meter will return to measurement mode (there will be a black box with MEAS written in it).

8. Open the light shield cover and tip out the pH buffer 7. Then remove moisture on the sensor by gently dabbing with a soft tissue.

9. Repeat steps 4 -7 using pH buffer.

10. Rinse the flat sensor with water and remove moisture by gently dabbing with a soft tissue. It is now ready for use. Calibration will hold for day of testing.

Part 3 : Measuring a Sample

1. Keep cover closed. Press the ON button on the meter until ‘P 11’ appears on the screen. A black box with MEAS in the left hand corner of the screen to indicate you are in measurement mode.

2. Open the light shield cover. Using a pipette, place a few drops of the water sample to be tested on the flat sensor to rinse and prepare the sensor. Alternatively, the meter can be dipped into the water sample.

3. Blot away the sample on the sensor gently with a soft tissue.

The flat sensor is made of thin glass, do not wipe or push the flat sensor.

4. Place the meter on a flat surface. Once again using the pipette, place a few drops of the water sample to be tested on the flat sensor taking care to cover the entire sensor. Give the sensor a little jiggle to help spread the sample.

Alternatively, the meter can be dipped into the water sample.

5. Close the light shield cover.

The meter is measuring the water sample when the display shows only a black box with MEAS written on the screen. The smiley face will only appear when the measured value is stable.

6. When the measurement is stable a smiley face will display. Record this result on your data sheet.

7. To finish, open the light shield cover and tip out the sample. Clean with distilled water and remove moisture on the sensor by gently dabbing with a soft tissue.

8. Put some tap water in a beaker.

9. Rinse out the pippette with the tap water three times.

10. Use the pippette to cover the sensor with tap water. It is best to leave the sensor wet with tap water in between periods of testing.

Pack Up

  1. Close the cover.

  2. Turn off by pressing the power button firmly.

  3. Wipe the outside of the meter.

  4. Put back in the correct location in your kit.

  • pH reflects the acidity or alkalinity of the water.

    Water with a pH of 7 is neutral; lower pH levels indicate increasing acidity; while pH levels higher than 7 indicate increasingly alkaline.

    Each unit of change represents a tenfold change in acidity or alkalinity.