Question
How should pH and conductivity electrodes be cleaned?
Summary
pH and conductivity electrode cleaning
Answer
The best cleaning solution for an electrode depends on the type of contamination.
Common symptoms of a probe in need of cleaning:
Visit the Hach Sensor Maintenace Page for a complete listing of cleaning, refill, and maintenance solutions.
For additional pH cleaning recommendations, the pH Electrode Cleaning and Maintenance Guide is useful.
Common symptoms of a probe in need of cleaning:
- Slow response
- High asymmetry potential/Slope out of range
- Poor sensitivity/drifting, inaccurate readings
| pH probe cleaning recommendations | |||
| Contaminants | Use | Description | Comments |
| Fats, Oils, and Grease | Most common contaminants for water treatment applications (municipal and industrial markets) | 1. Soak in Electrode Cleaning Solution (Product # 2965249) for at least 2 hours or overnight. 2. Ethanol, 95% |
1. All Hach pH electrodes 2. Ideal for glass and epoxy bodies only |
| Limescale/Mineral Buildup | For the dissolution of mineral deposits, lime, and scale. |
Soak in HYDROCHLORIC ACID, 0.1N 1000ML (Product # 1481253) for no more than 5 minutes
|
All Hach pH electrodes |
| Proteins | For the regeneration of electrodes that usually measure samples with a high protein content, such as milk, cheese, meat, blood, or serum. | 1. Probe Cleaning Solution for Samples that Contain Proteins, 500 mL (Product # C20C370) 2. NaOH (2%) |
All Hach pH electrodes |
| Sulfides (Ag+ precipitation across junction) |
Black deposits appear on the junction when an electrode is used with an Ag/AgCI wire reference in samples containing sulfides, or reducing substances, The silver salts which are formed are dissolved in the thiourea solution. | Prepare 1 M Thiourea in 0.1 M HCl: Mix 76.12 g of THIOUREA, >99.0% into 1L of Hydrochloric Acid Standard Solution, 0.10 N, 1 L (Product # 1481253) and stir slowly to dissolve. | Ideal for glass and epoxy bodies only; preparation required. |
| General |
Common solution for most types of contamination | 1. Hydrochloric Acid Standard Solution, 0.10 N, 1 L (Product #1481253) 2. Dilute bleach solution: 1 part SODIUM HYPOCHLORITE, >10% AR to 10 parts deionized water. |
1. All Hach pH electrodes 2. Ideal for glass and epoxy bodies only; dilution required. |
| Conductivity probe cleaning recommendations | |||
| Fats, Oils and Grease | Most common contaminants for water treatment applications (municipal and industrial markets) | 1. Soak in Electrode Cleaning Solution (Product # 2965249) for at least 2 hours or overnight. 2. Ethanol, 95% |
Suitable for all Hach EC cells |
| Limescale/Mineral Buildup | For the dissolution of mineral deposits, lime, and scale | Soak in HYDROCHLORIC ACID, 0.1N 1000ML (Product # 1481253) for no more than 5 minutes | Suitable for all Hach EC cells |
Visit the Hach Sensor Maintenace Page for a complete listing of cleaning, refill, and maintenance solutions.
For additional pH cleaning recommendations, the pH Electrode Cleaning and Maintenance Guide is useful.