Salt bridge/Luggin capillary

The main functions of salt bridges

• To reduce the liquid junction potential;

• To prevent or reduce mutual contamination between the working electrode and the reference electrode solution.

• Luggin capillary belongs to a type of salt bridge. When there is current passing through the measuring battery, there is an Ohmic potential drop in the solution between the two electrodes, which is more significant for solutions with higher resistivity and higher current. In order to minimize its impact on potential measurement, the salt bridge glass tube is pulled into a capillary tube,it is Luggin capillary tube, the user need to place it as close as possible to the working electrode to reduce the Ohmic voltage drop.

Main technical parameters

• Specifications: straight, curved, L-shaped 

• Filling solution: KCl, etc. (refer to point 2 of the usage and maintenance instructions) 

• Salt bridge liquid choroid flow rate: ≥ 15 minutes/1 drop (using potassium chloride test as the standard, with the upper end sealed) 

• Luggin capillary flow rate: ≥ 30 secs/1 drop (using distilled water test as the standard, upper end sealed)

 Instructions for use and maintenance

• 1. Slowly pour the filling liquid into the salt bridge/Luggin capillary tube in small amounts and multiple times along the vessel wall. Do not pour a large amount of solution at once, which may cause too many bubbles and be difficult to handle. After pouring the solution, check for any bubbles at the bottom. If there are bubbles, you can gently shake the upper end with your hand. You could use an ear wash ball to blow hard a few times until all the bubbles disappear if the bubbles still exist,. In case the bubbles still cannot be removed, please pour out all the filling liquid and repeat the operation. 

• 2. Selection of filling solution: To prevent or reduce mutual contamination between the working electrode and the reference electrode solution, the same solution as the filling solution in the reference electrode can be selected for filling; To protect the experimental system from contamination, the same solution as the experimental system can be selected for filling.

• 3. The filling fluid must be clean and free of impurities to prevent clogging of the tip and affecting the experiment.

• 4. It is recommended to replace the filling solution with a new one before and after each experiment to ensure the accuracy of the experiment.

• 5. It is not recommended to fill the Luggin capillary with agar. The viscosity of agar is high and it is not easy to completely fill the tip, it will cause a circuit breaker; besides it, agar is easily affected by temperature and humidity,  this will lead to volume deformation and poor contact. If the experiment requires filling with agar, you can contact us to customize a suitable aperture. Salt bridges can be used to fill agar. 

• When used for a long time in high concentration strong acid and alkali solutions, it can affect the flow rate of salt bridges/capillaries and reduce their service life.

• 7. The tip of the salt bridge/Luggin capillary should be as close as possible to the surface of the working electrode, but it should be a distance between them still, otherwise it will have a shielding effect on the electrode surface and affect the current distribution. Customers can adjust the distance according to experimental requirements. 

• 8. If the tip of the salt bridge/Luggin capillary tube is found to be blocked during use, ultrasound can be used. It is recommended to use ultrasound for no more than one minute each time. If it blocks still, repeat the operation. Do not use ultrasound for long time cleaning and it will cause damage.

• 9. When the salt bridge/Luggin capillary is placed in the electrolytic cell, the tip should not directly touch the bottom of the electrolytic cell to prevent it from any tip damage or blockage.

• 10. If the Salt bridge/Luggin capillary tube is frequently used, it can be soaked in the corresponding filling solution for storage. When it is not used for a long time, it needs to be rinsed clean and ensure that there is no residual solution at the tip. After drying thoroughly, it should be sealed and stored.