The quality of data collected depends heavily on measurement techniques applied. Adhere to the following guidelines for best results:

  • Calibrate and measure all samples at the same temperature. Recalibrate if the temperature of the probe’s operating environment changes significantly.
  • Dilute concentrated samples (over 0.1 M) prior to measurement.
  • The fastfill sleeve should be open (down) during measurements (see Figure 1).
  • The reference filling solution level should be higher than the sample level (see Figure 1).
  • The sample level should be higher than the immersion line on the probe (see Figure 1).
  • Do not allow air bubbles on the sensing module during measurements. Gently tap the sensor to remove bubbles if they exist.
  • Always rinse electrodes with distilled or deionized water between measurements.
  • Blot the sensor dry, never rub dry.
  • Stir the sample whenever possible. Stirring decreases the amount of time for the sensor to equilibrate and readings to stabilize.
  • Stir thoroughly at a slow to moderate speed using either a magnetic stirrer or the probe as the stirring rod.
  • Stirring rate should be consistent among all samples and standards.
  • Magnetic stirrers may generate enough heat to change solution temperature. A piece of insulating material such as cork, cardboard, or Styrofoam can be placed between the stir plate and sample container to help minimize heat transfer.
  • Add ionic strength adjuster to samples in a 1:50 ratio for all WQSensors except for the WQ-FL. For example, add 2 mL of ISA for each 100 mL sample. Adding ISA in a 1:50 ratio adjusts samples and standards to comparable pH levels.
  • For the WQ-FL Fluoride Smart USB Sensor: Add ionic strength adjuster to samples in a 1:1 ratio. For example, add 100 mL of ISA for each 100 mL sample. Adding ISA in a 1:1 ratio effectively masks interfering compounds or ions from the probe. Additionally the TISAB (total ionic strength adjustment buffer) has an acetate buffer at pH 5.4, which helps adjust the sample pH to the appropriate range.
  • Refer to WQ-DO Dissolved Oxygen Smart USB Sensor Measurement Techniques for additional guidelines for making dissolved oxygen measurements with the WQ-DO WQSensor.
Visual Summary of proper measurement techniques for ISE WQSensors

Figure 1: Visual Summary of Proper Measurement Techniques for ISE WQSensors

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