How to work with Mini Hydrogen Electrode Mini-HydroFlex

Before you start measuring, you must insert the supplied hydrogen cell (button cell) into the electrode head and place the mini hydrogen electrode in water for preferably 24 hours. Please do not remove the labelling with the serial number and the sticker with the activation date.

Commissioning of mini hydrogen electrode Mini-HydroFlex (youtube)

Commissioning of mini hydrogen electrode Mini-HydroFlex (pdf)

Manual for Mini-HydroFlex (pdf)

After your measurements, rinse the electrode thoroughly with water. Even when you are not measuring, please always place the mini hydrogen electrode in a liquid, e.g. measuring solution, 1 mol/l hydrochloric acid or 1 mol/l caustic soda. Hydrogen electrodes must not be stored dry in air!

Manual for Mini-HydroFlex (pdf)

Yes, Mini-HydroFlex is an electrode of the first kind. You can place Mini-HydroFlex directly into any kind of electrolyte.

After your measurements, rinse the electrode thoroughly with water. Even when you are not measuring, please always place the mini hydrogen electrode in a liquid, e.g. measuring solution, 1 mol/l hydrochloric acid or 1 mol/l caustic soda. Hydrogen electrodes must not be stored dry in air!

Manual for Mini-HydroFlex (pdf)

Nothing to do - Mini-HydroFlex is working without an internal buffer!

If you want to check Mini-HydroFlex, we recommend the standard calomel electrode or, if necessary, the silver silver chloride electrode. We recommend buffer pH 2.

A more detailed description can be found here.

Checking hydrogen electrode Mini-HydroFlex in buffer pH2 with mercury mercury-chloride electrode (pdf)

Checking hydrogen electrode Mini-HydroFlex in buffer pH 2 with silver silver-chloride electrode (pdf)

After reaching the runtime of 12 months, the hydrogen button cell has to be replaced. Exceeding the operating time can lead to defects of the hydrogen electrode and must be absolutely avoided.
If the replacement of the hydrogen cell is not possible, the hydrogen electrode has to be taken out of the liquid and stored dry until a new hydrogen cell can be inserted.

Replacment of hydrogen cell (youtube)

Replacement of hydrogen cell (pdf)

Manual for Mini-HydroFlex (pdf)

Hydrogen production is very low (approx. 1 ml per day). Therefore, it is rare for hydrogen bubbles to become visible.
If the potentials are all right, the reference electrode is working. Check the potentials once a week or once a month against an Ag/AgCl electrode in a pH 2 or pH 4 buffer.
Note the necessary replacement of the hydrogen cells.

Commissioning of mini hydrogen electrode Mini-HydroFlex (youtube)

Commissioning of mini hydrogen electrode Mini-HydroFlex (pdf)

Manual for Mini-HydroFlex (pdf)

1. Poor contacting
   Check the measuring cables for optical damages such as corrosion, cracks and sessile plugs. Replace the cable. Check the electrode with an external reference electrode, e.g. a calomel or silver silver chloride electrode.
   Checking hydrogen electrode Mini-HydroFlex in buffer pH2 with mercury mercury-chloride electrode (pdf)
   Checking hydrogen electrode Mini-HydroFlex in buffer pH 2 with silver silver-chloride electrode (pdf)
2. No or insufficient hydrogen production
   Did you place the new Mini-HydroFlex in the measuring solution for 24 hours? If not, wait 24 hours before measuring.
   Has the runtime of the hydrogen source been exceeded? If yes, please replace the hydrogen cell.
   Replacment of hydrogen cell (youtube)
   Replacement of hydrogen cell (pdf)
   Manual for Mini-HydroFlex (pdf)
3. Slow ion exchange, e.g. when switching from concentrated solutions to weakly concentrated solutions
   Please take the adjustment time into account, sometimes the balancing of concentrations takes longer than expected. If necessary, check the potential in another electrolyte such as 1 mol/l hydrochloric acid.
4. Air/oxygen reaches the electrode
   Avoid that gases such as air or oxygen reach the hydrogen electrode’s shaft. If this happens the hydrogen is displaced or reacts off. No hydrogen potential can be set.

1. Hydrogen bubbles from the hydrogen electrode itself
   Bubbles are continuously leaking out of the hydrogen electrode. Some bubbles are small, others are bigger. Usually, they do not disturb your measurements.
   Is a big bubble forming at the bottom of the hydrogen electrode which sticks to the vessel wall? If possible, place the electrode further away from the vessel wall or hang the hydrogen electrode transversely into the measuring vessel.
2. Induced gases
   Change the position of your gas inlet.
   Induced gas bubbles which are piped by close to the hydrogen electrode can disturb the measurements and lead to fluctuating potetnials.
3. Potentiostat or measuring device
   Check your measuring device. If you measure in poorly conductive electrolytes, potentiostats and measuring devices quickly reach their limits. More information about noise in electrochemical measurements can be found here: What-can-cause-my-experiment-to-be-noisy

The hydrogen electrode is contaminated and a mixed potential is set
Check the runtime of the hydrogen source. If necessary, the hydrogen cell must be replaced.
Some deposits can be wiped off with a cloth. With 1000 grit sandpaper, you can carefully sand the bottom of the electrode.
More stubborn impurities dissolve in 1 mol/l nitric acid. The electrode must then be rinsed thoroughly in distilled water.

If the cleaning steps are unsuccessful, the electrode is unfortunately so badly contaminated that we recommend buying a new one.