Are you testing for ultra low range Iron? Hach chemist Luke shows helpful tips for performing Hach’s Ultra Low Range Total Iron Method. This method is designed to analyze both particulate and dissolved Iron in ultrapure water. 


We're having trouble posting the video. You can find it here: 


Any questions for Luke? 



Today's pH probe cleaning method is specific to biological growth. Like Protein, or Oil/Fats, this is a shorter method. Is it similar to what you are already doing? Or different? we'd be interested in hearing what you do. 


Biological growth

1. First place probe tip for 10 min. in PEPSIN-IN-HCL solution.

2. Then for 1 min. in THIO-UREA solution.

3. Rinse thoroughly with deionized water and dry with a cloth.


As a final bonus for sticking with us through all the cleaning process we'll throw in this final tip from our application experts. 

For a “mild” disinfection the electrode can be placed for 10-20 min. in a 3% hydrogen peroxide solution (H2O2). Afterwards rinse thoroughly with deionized water and calibrate.



Wildlands is a science research charter school formed in partnership between Agusta School district and Beaver Creek Reserve. Their focus to build a student focused learning environment based on independent thinking and real world preparation. One of their YouTube videos - Testing Water for Nitrate can be seen below. Looks like the video is an education based, "how to". What do you think? 



Are you testing pH in waste water or sludge applications? How does our probe cleaning process compare to yours? 


Waste water / sludge

1. Remove remaining contamination by rinsing with 40°C warm tap water.

2. Place probe tip for 5 min. in HYPOCHLORITE solution.

3. Then 5 min. PEPSIN-IN-HCL and finally for 10 min. DETERGENT solution.

4. Rinse thoroughly with deionized water and dry with a cloth.

5. Check, whether glass bulb and diaphragm are clean.


Testing pH in a protein application? What is your probe cleaning process? Are you having problems with accuracy or reliability? Try the cleaning process below. Have you tried any of the other cleaning processes? What do you think? 



1. First place probe tip for 10 min. in PEPSIN-IN-HCL solution.

2. Then for 1 min. in THIO-UREA solution.

3. Rinse thoroughly with deionized water and dry with a cloth.


Are you testing pH in oil / fat substances? We have outlined a specific cleaning solution for your pH probes. There is an old quote about being able to tell what kind of a craftsmen you are dealing with by how they take care of their tools. How are you treating your probes? Try this cleaning method for your probes being used in oil / fat. 


Oil / Fat

1. Place probe tip for 10-20 min. in a warm (40°C) DETERGENT solution.

2. Then quickly rinse with acetone and then with ethanol.

3. Rinse thoroughly with deionized water and dry with a cloth.


During this series of pH probe cleaning tips, we identify a number of cleaning solutions. below is a table of the items we reference, just in case you were wondering. 



Cleaning Solution Part NumberType of Sample / Contamination
DetergentS16M001clean water, light fatty/oil
HypochloriteS16M002dirty of biological active sample
Thio ureaC20C380containing sulphides or metal ions
Pepsin in HClC20C370biological / medical samples
Phosphoric acid2975149inorganic samples 




Are you dealing with sulfide contamination? How does it affect your pH probes? Did you know that a specific cleaning treatment can help protect/maintain your probes? Use the following process to ensure accuracy and longevity of your probes. 

Sulfide contamination

1. Rinse thoroughly with tap water and dry with a cloth.

2. Place probe tip for 20-30 min. in THIO-UREA solution.

3. Then 10 min. in DETERGENT solution.

3. Rinse thoroughly with deionized water and dry with a cloth.

4. With liquid filled probes, replace the inner electrolyte.


Continuing our series of application specific pH probe cleaning, today we have identified an organic chemicals scenario. Are you testing pH in organic chemicals? Are you using a specific cleaning process to optimize the life of your probe? Our application experts have identified the following process:


Organic chemicals

1. Remove remaining organic compounds or solvents with acetone and then

    rinse with ethanol. Thoroughly rinse with tap water.

2. Place probe for 10 minutes in DETERGENT solution.

3. Rinse thoroughly with deionized water and dry with a cloth.

4. Check, whether the treatment in organic chemicals has attacked or damaged

    the probe body or diaphragm.


Does this match up with what you are doing? Do you do something different? 


Do you believe cleaning pH probes with water is sufficient? Do your pH probes have increasing response time and shorter lifetime? We've spoken with our application experts and identified optimal cleaning process for pH probes across a broad range of applications. For the next several days we'll be publishing each of the application specific cleaning techniques. Today's application - Inorganic chemicals. How does our cleaning procedure compare with what you are doing?


Inorganic chemicals

1. Rinse remaining acids and bases with tap water

2. Place probe for 5 minutes in PHOSPHORIC-ACID, then 10 min. in. 

    DETERGENT solution

3. Rinse thoroughly with deionized water and dry with a cloth



Until today, the only international norms for the measurement of dissolved oxygen were ISO 5813 “Winkler-Titration Method” and ISO 5814 “Electrochemical probe method”. Everybody measuring the amount of oxygen dissolved in water samples was “officially” not allowed to use the new HACH LDO (luminescent dissolved oxygen) probe for reporting. Now the situation has changed!

ISO 17289 describes the “optical method” as being equivalent to the “Winkler” or “electrochemical” methods, for both online and lab/field measurements. This enables all users measuring dissolved oxygen to use the LDO probe and the much more reliable and user-friendly optical DO method.


ADVANTAGES of LDO technology:


  •   Ready to measure right after power on
  •   Stable reading within short time
  •   Reliable readings
  •   Longer lifetime
  •   Simple calibration with 100% and 0% DO standards


  •   No start up time
  •   No polarization time
  •   No refilling of electrolyte
  •   No polishing of inner electrodes
  •   No poisoning of inner electrodes
  •   No frequent change of membranes
  •   No specific conditioning
  •   No or slow stirring required


Following the Hach-Lange tradition of environmental responsibility (e.g. see our environmental recycling center in Düsseldorf), we introduced an alternative 0% DO standard in the new DIN and ISO norm. Because the existing 0% DO standard with Na2SO3 + CoCl2 (sodium sulfite + cobalt chloride) is hazardous, Hach-Lange introduced a new recipe for a non-hazardous O% DO standard. Read here how to prepare the safe 0% DO standard solution:


New non-hazardous 0% DO standard solution

  • deionized water
  • ascorbic acid
  • sodium hydroxide solution, NaOH 1 mol/l


Prepare the alkaline ascorbic acid solution by dissolving 2 g ascorbic acid and 25 ml 1 mol/l NaOH in 85 ml deionized water in a vessel with stopper (in total 110 ml solution). Stir slowly for at least 3 minutes before use. Always keep the 0% DO solution closed to avoid uptake of oxygen from ambient air. Under such conditions, the solution will maintain stability for at least 6 hours. (Please note, the DO probe may need up to 5 minutes or even longer to reach the 0.0% DO reading.)


The new ISO 17289 Norm, in English language only, can be ordered online from: