How to work with Hydrogen Electrode HydroFlex

Before the first use, the hydrogen electrode HydroFlex must be activated so that hydrogen production can start in the hydrogen generation cell. To do this, carefully remove the protective cap from the electrode. Turn the runtime on the head of the electrode clockwise to position 1 using a 3 mm hex screw driver.
Place HydroFlex in distilled water for 24 hours. At least half of the shaft should be surrounded by water. After 24 hours, adjust the runtime to 6 months. For correct use, this must not be changed.
Important: Please mark the activation month and year on the enclosed sticker and attach it to the HydroFlex.
Please do not remove the labelling with the serial number and the sticker with the activation date.

Commissioning of hydrogen electrode HydroFlex (youtube)

Commissioning of hydrogen electrode HydroFlex (pdf)

Manual for HydroFlex (pdf)

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

After the measurements, rinse the electrode thoroughly with water. Place the hydrogen electrode in a liquid (such as measuring solution, 1 mol/l hydrochloric acid, 1 mol/l sodium hydroxide solution, water) to keep it functional. The hydrogen electrode should not be stored dry in air as long as the hydrogen cartridge is generating hydrogen - even when you are not measuring. Otherwise, a mixed potential forms which can lead to incorrect results.
Pay attention to the runtime of the hydrogen cartridge. As soon as the runtime of 6 months is reached, the hydrogen cartridge must be replaced immediately. Otherwise, a vacuum will form in the electrode and liquid can be soaked.

Manual for HydroFlex (pdf)

After the measurements, rinse the electrode thoroughly with water. Place the hydrogen electrode in a liquid (such as measuring solution, 1 mol/l hydrochloric acid, 1 mol/l sodium hydroxide solution, water) to keep it functional. The hydrogen electrode should not be stored dry in air as long as the hydrogen cartridge is generating hydrogen - even when you are not measuring. Otherwise, a mixed potential forms which can lead to incorrect results.
Pay attention to the runtime of the hydrogen cartridge. As soon as the runtime of 6 months is reached, the hydrogen cartridge must be replaced immediately. Otherwise, a vacuum will form in the electrode and liquid can be soaked.

Manual for HydroFlex (pdf)

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

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

A more detailed description ican be found here.

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

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

Sometimes a complete cleaning of the HydroFlex is required – especially when there are visible deposits on the electrode.

Cleaning of hydrogen electrode HydroFlex (pdf)

Cleaning (Youtube) 

Manual for HydroFlex (pdf)

As soon as the running time of 6 months is reached, the hydrogen cartridge must be replaced immediately. Otherwise, a vacuum will form in the electrode and liquid can be soaked.
You can remove the old hydrogen supply with a SW21-ring-spanner and replace it with a new one. Mind the correct hub of the O-ring when you install the new hydrogen supply. The O-ring must not push itself out. Seal the screw thread with a universal grease (e.g. Korasilon-paste highly viscous). The spent cartridge has to be disposed of as battery garbage.
If it is not possible to change the hydrogen cartridge, the hydrogen electrode must be removed from the liquid and stored dry until a new hydrogen cartridge can be inserted.

Replacment of hydrogen cartridge (youtube)

Replacement of hydrogen cartridge (pdf)

Manual for 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 hydrogen electrode HydroFlex (youtube)

Commissioning of hydrogen electrode HydroFlex (pdf)

Manual for HydroFlex (pdf)

1. Poor contacting
   Check the measuring cables for optical damages such as corrosion, cracks and sessile plugs. Replace the cables. Check the electrode with an external reference electrode, e.g. a calomel or silver silver chloride electrode.
   Checking hydrogen electrode HydroFlex in buffer pH2 with mercury mercury-chloride electrode (pdf)
   Checking hydrogen electrode HydroFlex in buffer pH 2 with silver silver-chloride electrode (pdf)
2. No or insufficient hydrogen production
   Did you place the new 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 cartridge.
   Replacment of hydrogen cartridge (youtube)
   Replacement of hydrogen cartridge (pdf)
   Manual for 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 hydrogen 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 potentials.
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 cartridge 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 necessary, you can try a compete cleaning of the HydroFlex.

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