3. Water & Environmental / Water Analysers

How do I look after my LAQUAtwin Sensor?

Proper usage and maintenance of the LAQUAtwin pH and Ion meters, especially the sensors that come in contact with samples, is important to maintain the accuracy and prolong the life span of the instrument. Below is a list of procedures to followed to properly maintain your meter. If the sensor itself is damaged, scratched or cracked then the meter is not useable and the sensor will need replacing.

What is needed?

For any cleaning the basic material required are cotton buds, soft tissue (ideally lint-free) and distilled, deionised or tap water. In addition:

pH sensors also require

  • pH buffer 7.00 (1192704)
  • Cleaning Solution 220 (1222067) – contains 10% thiourea and 1% hydrochloric acid (HCl) for removing inorganic residues on sensing membrane and junction
  • Cleaning Solution 250 (1222069) – contains < 0.5% enzyme protease, < 0.1% sodium azide, and other ingredients for removing protein residues on sensing membrane and junction
  • Household bleach (< 5% sodium hypochlorite or NaClO)

Ions sensors also require

  • 2000ppm Ion Standard Solution
  • Household bleach (< 5% sodium hypochlorite or NaClO)
  • A mild detergent

Conditioning

Dry sensors may give an erratic reading or slow response. Condition the sensors before using it for the first time and after storing it dry. If there is a white powder or salt buildup on the junction after dry storage, simply rinse off with water. This is normal.

For pH Sensors

  1. Place a few drops of pH 7.00 buffer onto the pH sensor. Make sure that the whole flat sensor is covered with the solution.
  2. Leave the pH buffer for at least 1 hour to allow the solution to hydrate the pH sensor.
  3. Rinse the pH sensor with water and blot it dry with soft tissue.
  4. Perform calibration with fresh pH buffers prior to sample measurement.

For Ion Sensors

  1. Place a few drops of 2000ppm ion standard solution onto the ion sensor. Make sure that the whole flat sensor is covered with the solution.
  2. Leave the standard solution on the ion sensor for 10 minutes to 1 hour.
  3. Rinse the ion sensor with water and blot it dry with soft tissue.
  4. Perform calibration with fresh ion standard solutions prior to sample measurement.

 

Cleaning

For pH Sensors

A clean pH sensor is necessary for performing an accurate pH measurement. The cleaning solution will depend on what sample was tested with the sensor.

Read the safety data sheet (SDS) of the cleaning solution to be used and wear the proper personal protective equipment before handling.

  1. Remove unwanted sample residues left on the pH sensor by using an appropriate cleaning solution. For most samples, use a mild detergent and clean water. For samples containing oil, proteins, and stain-causing substances, use the indicated cleaning solutions below.
    • Oils – place a few drops of warm water and mild detergent solution onto the sensor. Never use any organic solvent (e.g., acetone, ethanol, etc.) to clean the pH sensor as it may cause damage and shorten the sensor lifespan. This usage will also void the sensor warranty.
    • Proteins – place a few drops of cleaning solution 250 (1222069) onto the sensor and leave for 30 minutes.
    • Stains – place a few drops of cleaning solution 220 (1222067) or 0.1 M HCl onto the sensor and leave for 30 minutes.
  2. Gently, wipe the sensor using a cotton bud. Avoid applying pressure and repeat step 1, if needed.
  3. Rinse the pH sensor with water and condition it (See Conditioning).

If calibration with fresh buffers fails repeatedly and cleaning does not restore the pH sensor performance, replace the pH sensor with a new one (1192697). The pH sensor is a consumable product and its performance deteriorates over time even under normal operating condition. When disinfection is required wipe the surface of the meter body (not sensor) with a clean cloth wet with ethanol or use alcohol wipes for pH sensors.

 

For Ion Sensors

The performance of the ion sensor may deteriorate, especially when it is used in testing dirty samples such as soil, plant tissue sap, etc.  To restore the performance of the ion sensor, remove any unwanted sample residues on the flat sensor surface by cleaning it with mild detergent and water. If there are stains or stubborn deposits left, perform the following:

  1. Place a few drops of household bleach with less than 5% sodium hypochlorite onto the sensor and leave for 5 to 30 minutes (maximum).
  2. Gently, wipe the sensor using a cotton bud. Avoid applying pressure and repeat step 1, if needed.
  3. Rinse the ion sensor with water and condition it (See Conditioning).

Sodium hypochlorite (NaClO) salt is the active ingredient of bleach, which is often used in disinfection and stain removal. Generally, household bleach in the market contains 3 to 8% NaClO. For cleaning the sensor, a cleaning solution with less than 5% NaClO is recommended, so dilute bleach if necessary.

If calibration with fresh ion standard solutions fails repeatedly and cleaning does not restore the ion sensor performance, replace the sensor with a new one (See Part Numbers below). The ion sensor is a consumable product and its performance deteriorates over time even under normal operating condition.

  • 1192699 – Sodium-Ion Sensor
  • 1227820 –  Salt Sensor
  • 1192700 – Salt EC Sensor
  • 1192701– Potassium Ion Sensor
  • 1192702 – Nitrate Ion Sensor
  • 1192703 – Calcium Ion Sensor

When disinfection of sensors is required place drops of 5% sodium hypochlorite (NaClO) solution for 5 to 30 minutes then rinse thoroughly with sterile water.

Storage

Store the clean sensor in dry condition. Never leave distilled or deionized water on the sensor for a long period as salts may leach out and reduce sensor life. Condition the sensor prior to next use based on the sensor type (see above).

 

For further information contact support@camlab.co.uk.