HydroFlex® as RHE (Reversible Hydrogen Electrode)

The most common use of HydroFlex in the daily lab routine certainly is the application as RHE. You simply dip HydroFlex into your solution, directly. The advantages are obvious. You don't need a liquid junction, you don't have diffusion potentials and you don't contaminate your solution by ions flowing out of your reference system.
As HydroFlex needs no maintanance except the regular exchange of the H2-Cartridge every 6 months, it is very well applicable for long-term tests.

HydroFlex® as NHE (Normal Hydrogen Electrode)

HydroFlex works as a NHE, if you put it into hydrochloric acid at a concentration of 1 mol/l and ambient pressure. The potential differences between a NHE and a standard hydrogen electrode are small while the experimental complexity is easily manageable.

HydroFlex® as SHE (Standard Hydrogen Electrode)

The experimental complexity of using HydroFlex as SHE is comparably high. In this case HydroFlex has to be dipped into a solution with hydrogen ion activity of 1 mol/l. The temperature has to be 298,15 K (77 °F) and the pressure has to be 1013,3 hPa (14,697 psi). As the verification of these standard conditions is challenging, the use of HydroFlex as SHE usually is irrelevant in the daily routine.

So far we tested HydroFlex® in these solutions:

LiOH lithium hydroxide OK!
NaOH sodium hydroxide (caustic soda) OK!
KOH potassium hydroxide (caustic potash) OK!
HCl hydrochloric acid OK!
NaCl sodium chloride (common salt solution) OK!
KCl potassium chloride OK!
H2SO4 < 50 % sulphurir acid OK!
H3PO4 phosphoric acid OK!
HF hydrofluoric acid OK!
HClO hypochlorous acid OK!
HClO4 perchloric acid OK!
H2CO3 carbonic acid OK!
HCOOH formic acid OK!
CH)3COOH acetic acid OK!
C6H5COOH benzoic acid OK!
C3H6O3 lactic acid OK!
C6H8O7 citric acid OK!
CH)2(COOH)2 maleic acid OK!
HNO3 nitric acid Not OK!
HNO3 / HCl nitrohydrochloric acid (aqua regia) OK!

If you are looking for a solution not mentioned in the table above, it does not necessarily mean that HydroFlex® can't be used in your application. It only means that we did not yet test it.
Please do not hesitate to contact us in this case!