Vernier Chloride Ion-Selective Electrode User Manual

Chloride Ion-Selective Electrode

(Order Code CL-BTA)

The Vernier Chloride Ion-Selective Electrode is used to measure the concentration of chloride (Cl−) ions in aqueous samples.

Note: Vernier products are designed for educational use. Our products are not designed nor are they recommended for any industrial, medical, or commercial process such as life support, patient diagnosis, control of a manufacturing process, or industrial testing of any kind.

What's Included

l Chloride Ion-Selective Electrode, packed in a storage bottle l 30 mL bottle of High Standard solution with SDS (1000 mg/L Cl l 30 mL bottle of Low Standard solution with SDS(10 mg/L Cl l Short-Term ISESoaking Bottle

Compatible Software and Interfaces

See www.vernier.com/manuals/cl-bt a for a list of software compatible with the Chloride Ion-Selective Electrode.

Getting Started

1. Prepare the electrode by soaking it in the High Standard solution for 30 minutes. Refer to the next section for more information.

2. Connect the sensor to the interface (LabQuest Mini, LabQuest 3, etc.)

3. Start the appropriate data-collection software (Graphical Analysis, LabQuest App, Logger Pro) if not already running. The software will identify the sensor and load a default data-collection setup.

4. Perform a two-point calibration using the High and Low Standard solutions. Refer to the next section for more information.

If you are collecting data using a Chromebook™, mobile device such as iPad or Android™ tablet, or a Vernier wireless sensor or interface, please see the following link for up-to-date connection information:

www.vernier.com/start/cl- bta

Preparing the Chloride ISE for Use

Note: Follow this two-part process before taking measurements with your ISE.

Part I: Soak the Electrode

Soak the electrode in the High Standard solution (included with the ISE) for approximately 30minutes. The ISE should not rest on the bottom of the container, and the small white reference contacts near the tip of the electrode should be immersed. Make sure no air bubbles are trapped below the ISE. Important: Do not leave the ISE soaking for more than 24hours. Important: If

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you plan to use the electrode outside the range of the standards provided, you will need to prepare your own standards and use those for soaking.

Note: If the ISE needs to be transported to the field during the soaking process, use the Short-Term ISE Soaking Bottle. Remove the cap from the bottle and fill it 3/4 full with High Standard. Slide the bottle’s cap onto the ISE, insert it into the bottle, and tighten.

For long-term storage, greater than 24 hours, make sure the sensor is stored in its storage bottle with the sponge slightly damp.

Part II: Calibrate the ISE

Calibrating the Chloride ISE in Graphical Analysis 4

1. Connect the sensor according to the Getting Started section.

2. Click or tap the live readouts meter and choose Calibrate.

3. High Standard Calibration Point: The Chloride ISE should still be soaking in the High Standard. The ISE should not rest on the bottom of the container, and the 2 small white reference contacts near the tip of the electrode should be immersed. Make sure no air bubbles are trapped below the ISE.

4. Enter the concentration value of the High Standard (e.g., 100 for 100 mg/L) in the edit box and click or tap Keep.

5. Low Standard Calibration Point: Remove the ISE from the High Standard, rinse well with distilled water, and gently blot the ISE dry with a paper towel. Place the ISE into the Low Standard. Make sure the ISE is not resting on the bottom of the container, the white reference contacts near the tip of the electrode are immersed, and no air bubbles are trapped below the ISE.

6. Enter the concentration value for the Low Standard (e.g., 1 for 1 mg/L) and click or tap Keep .

7. Click or tap Apply to complete the calibration process.

Calibrating the Chloride ISE in Logg er Pro 3

1. Connect the sensor according to the Getting Started section.

Choose Calibrate from the Experiment menu and then click .

4. Enter the concentration value of the High Standard (e.g., 100 for 100 mg/L) in the edit box.

5. After the voltage reading for Reading 1 stabilizes (~2 minutes), click

6. Low Standard Calibration Point: Remove the ISE from the High Standard, rinse well with distilled water, and gently blot the ISE dry with a paper towel. Place the ISE into the Low Standard. Make sure the ISE is not resting on the bottom of the container, the white reference contacts near the tip of the electrode are immersed, and no air bubbles are trapped below the ISE.

7. Enter the concentration value for the Low Standard (e.g., 1 for 1 mg/L).

After the voltage reading stabilizes, click .

9. To save the calibration to the sensor, follow the steps below: a. Click the Calibration Storage tab at the top of the dialog box.

Click . Click .

Click to continue. Click to complete the process.

Calibrating the Chloride ISE with LabQuest App

1. Connect the Chloride ISE to LabQuest. Choose Calibrate from the Sensors

menu and select Calibrate Now.

2. High Standard Calibration Point: The Chloride ISE should still be soaking

in the High Standard. The ISE should not rest on the bottom of the container, and the small white reference contacts near the tip of the electrode should be immersed. Make sure no air bubbles are trapped below the ISE.

3. Enter the concentration of the High Standard (e.g., 100 for 100 mg/L) for

Reading 1.

4. After the voltage reading stabilizes (~2 minutes), tap Keep.

5. Low Standard Calibration Point: Remove the ISE from the High Standard,

rinse well with distilled water, and gently blot the ISE dry with a paper towel. Place the ISE into the Low Standard. Make sure the ISE is not resting on the bottom of the container, the white reference contacts near the tip of the electrode are immersed, and no air bubbles are trapped below the ISE.

6. Enter the concentration of the Low Standard (e.g., 1 for 1 mg/L) for Reading

7. After the voltage reading stabilizes, tap Keep.

8. To save the calibration to the sensor, follow the steps below: a. Tap Storage.

b. Tap Save Calibration to Sensor. Tap OK.

c. Tap OK to complete the process.

Using the Product

Chloride ions are found in freshwater samples as a result of water flowing over salt-containing minerals. These salts might include either sodium chloride (NaCl) or potassium chloride (KCl). The EPA maximum contamination level for chloride concentration in drinking water is 250mg/L. The chloride ion concentration in seawater is approximately 19,400mg/L—well below the upper limit of the Chloride ISE of 35,500mg/L.

When the response of the Chloride ISE begins to slow, the membrane may need polishing. Cut a small piece (about 1 inch square) from a polishing strip. Wet the end of the electrode and the dull side of the polishing strip thoroughly with distilled water. Using only moderate pressure, polish the end of the electrode by gently rubbing it in a circular motion. This will remove the inactive layer of the membrane which impedes measurement. Rinse thoroughly with distilled water and recalibrate in the usual manner.

Sampling Freshwater Samples for Chloride Concentration

For best results, calibrate the Chloride ISE using the 10 mg/L and 1000 mg/L standards.

How Can I Have My ISE Read mV Output Instead of mg/L?

If you would like to have your ISE read mV output instead of mg/L, the amplification equation is:

V = 0.00727*mV + 1.223

Therefore, the reverse amplification equation, solving for mV, would be:

mV = 137.55*V – 0.1682

Measuring Chloride Concentration of Saltwater or Brackish Water

When measuring chloride concentration in seawater or brackish water, calibrate the Chloride ISE using the 1000 mg/L standard included with your Chloride ISE for one calibration point (or 1.806 parts per thousand, or ppt). For the second calibration point, prepare a standard that is 20,000 mg/L Cl–by adding 32.96 g of solid NaCl to enough distilled water to prepare 1 L of solution:

If you are calibrating in ppt, call this solution 36.13 ppt.

Determinin g Salin ity o f Saltwater or Brackish Water

Salinity is the total of all salts dissolved in water, expressed either as mg/L (equal to parts per million, ppm) or in parts per thousand (ppt). Seawater contains a fairly constant quantity of chloride ions. From your measurement of chloride ion concentration (in the previous section), salinity can be calculated using the following formula:

Salinity (mg/L or ppm) = 1.8066 × [Cl–concentration, mg/L]

Using this formula, the salinity of saltwater is calculated to be:

Salinity (mg/L or ppm) = 1.8066 × (19400 mg/L) = 35,000 mg/L

The level of salinity of seawater in parts per thousand, or ppt, would be:

Salinity (ppt) = 35,000 / 1,000 = 35 ppt

Collecting Data

1. Make sure the sensor is properly calibrated. If the meter has a reading of

1.0mg/L and the sensor is not in a 1.0 mg/L solution, you need to calibrate. After calibration, rinse off the tip of the ISE and blot it dry with a paper towel.

2. Insert the tip of the ISE into the aqueous sample to be tested. Important: Make sure the ISE is not resting on the bottom of the container, the white reference contacts near the tip of the electrode are immersed, and no air bubbles are trapped below the ISE. Note: Do not completely submerge the sensor. The handle is not waterproof.

3. Hold the ISE still until the reading stabilizes and record the displayed reading. Note: With some aqueous samples, especially those at high

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