How should pH and conductivity electrodes be cleaned?

Dokument-ID

Dokument-ID TE2707

Veröffentlichungsdatum

Veröffentlichungsdatum 14.06.2022
Frage
How should pH and conductivity electrodes be cleaned?
Zusammenfassung
pH and conductivity electrode cleaning
Antwort
The best cleaning solution for an electrode depends on the type of contamination.

Common symptoms of a probe in need of cleaning:
  1. Slow response
  2. High asymmetry potential/Slope out of range
  3. 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 Data Sheet: HQd pH Electrode Cleaning and Maintenance Guide_LIT2781 is useful.

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