US Long-Term Ecological Research Network

(used for Biocomplexity Cross Lake Comparison Samples in 2004)


  1. Press STBY/MEAS key to take the meter off standby. Press MODE until meter shows MEASURING PH. Press MULTI-POINT CAL. Key in 3 and press ENTER. Meter will prompt for first buffer value.
  2. Place meter on standby, rinse and fill electrode chamber with pH 6.86 buffer. Key in 6.86 and press ENTER. Wait for four asterisk stability indicator to appear after the ENTER MV message, then record the millivolt value on the lab data sheet. Press ENTER. Meter will ask for a temperature; key in and ENTER the room temperature read from the thermometer in the lab.
  3. Meter will prompt for second buffer. Repeat step 2 with pH 4.00 buffer. After you have pressed ENTER for the second buffer, the meter will display an efficiency value. A value of 1.00 would indicate a perfect electrode; a value between 0.95 and 1.05 is acceptable. Press ENTER to continue if the efficiency is acceptable.
  4. Meter will prompt for third buffer. Repeat step 2 with pH 3.557 buffer. The meter will again display an efficiency value after you enter the buffer mV value. Press ENTER to continue if the efficiency is acceptable.
Before pH analysis
  • Warm samples to room temperature in a dark container.
  • Fill the electrode syringe chamber with a sample of lake water from one of the conditioning vials. Allow electrode to soak for at least 15 minutes.
  • Bubble air through the samples in widemouth bottles. Use air from outside the lab and bubble for at least 5 minutes. Cap tightly until analysis.
Sample analysis
Press MODE until the meter displays MEASURING MV, then return meter to standby. The meter should be placed on standby whenever the electrode is not in liquid, including for all rinses.
Rinse electrode and run sample aliquots with a syringe the same as for the old system.
For each aliquot, wait for the stability indicator (‘) to show between MV and A on the meter display, then record the mV value on lab data sheet.
Run aliquots from the same vial until two consecutive readings are within 1 mV.
  • Rinse and fill electrode chamber with Trout Lake water. Tape electrode filling solution hole tightly.
  • Place pH meter on standby.
  • Rinse sample bottles 3x with milliQ and leave out to dry.


LTER Keywords
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