How is the temperature compensated when measuring conductivity?
The conductivity measurement is strongly temperature-dependent (about 2% variation per °C). Results can only be compared if the temperature of all samples is identical or if the value refers to a certain reference temperature.
Most often the linear temperature compensation is used. The operator has to select 20 °C or 25 °C as the reference temperature. The difference between the measured and reference temperature is multiplied with a compensation factor called α (alpha, unit %/°C). The conductivity reading is then compensated with this percentage.
To have the correct temperature compensation when measuring the conductivity, the linear compensation coefficient alpha must be determined for each kind of sample. By approximation, the temperature dependence is taken as linear. But in reality this “linear” coefficient itself depends on the ion concentration and temperature of the sample. The factory setting of alpha is 2.00 %/°C, which can appreciatively be used for standard samples. No icon is shown before the first calibration is carried out and saved.
How long can one use solutions once the bottle has been opened?
We guarantee that a solution in a freshly opened bottle meets its specifications provided that is still within its expiry date. However, as we have no means of knowing how a solution is stored once the bottle has been opened we cannot guarantee for the quality of the solution after that. We can only provide customers with tips and hints how to use the solutions as long as possible with accurate results. For example, it is known that acidic buffer solutions can be kept for longer than alkaline solutions. In alkaline solutions carbon dioxide from air may dissolve in the liquid and change the concentration of protons resulting in lower pH values.
Due to unforeseeable circumstances beyond our control, the only guarantee offered is for the quality of the solution in a previously unopened bottle (and only until the expiration date is reached).
We can only provide customers with tips and hints how to use the solution as long as possible for accurate results. For example it is known that acidic buffer solutions can be kept longer than alkaline ones since carbon dioxide from air may dissolve in the liquid and change the concentration of protons towards lower pH values.
A test certificate of all calibration solutions and many electrolytes can be downloaded by visiting Buffer