FAQ | In general
|How long can opened buffer solutions be used?
||Buffer solutions in glass vials are intended for single use. All other buffer solutions are marked with expiration dates.
|Are there differences between DIN and technical buffers?
||DIN buffer solutions are fixed in their composition (DIN 19266) and offer high accuracy. Technical buffer solutions can vary between manufacturers. Which buffer solution is used is therefore specific to the application.
|How do the electrode glasses differ? Which glass is suitable for which use?
||"The different electrode glasses differ in their composition and are optimized for different uses. H glass: is well suited for high temperatures in the acidic and alkaline range as well as for high concentrations of sodium ions S glass: in hot alkaline media with good reproducibility and a short response time L glass: for low temperatures and general applications A glass: with a short response time in drinking, domestic and waste water; for general applications and in low-ion media"
|When does it make sense to use ISE electrodes (measuring range, sample prerequisites)?
||The measuring range, sample preparation, and possible interferences are listed in the operating instructions for the ion selective electrodes.
|What do I watch for when using ISE electrodes?
||Ion selective electrodes by SI Analytic are fitted with a plastic electrode shaft. This shaft should to be tested for resistance to the measuring medium. ISE are suited only for use in laboratories and not for continuous process measurements. The sample preparation should be adhered to in detail.
|What does the incline/zero point of a ph electrode have to be in order to be able to measure sensibly? When should the electrode be replaced?
||The zero point should be between -25 and +25 mV, the incline between -56 and -61 mV/pH. If the values are outside the ranges, the electrode must be cleaned and the calibration must be performed once more. If the electrode cannot be improved by cleaning it, it must be replaced.
|Why are there air bubbles when attaching the hydration cap?
||When you attach the hydration cap, the air that remains inside of the cap is pressed into the electrode via the diaphragm due to the increased pressure, which is the reason for the rising bubbles. This effect is a good sign, as this proves the permeability of the diaphragm.
|Does an air bubble cause trouble in the glass electrode?
||As long as the conduction wire of the electrode is still protruding into the solution of the inner buffer, no interference must be feared.
|Why does the electrode lose KCl solution?
||When the refill opening is open, KCl solution will flow through the diaphragm into the measuring medium.
|Why can the one-rod measuring chain not be stored in distilled water?
||If the diaphragm is stored in distilled water, the electrolyte inside the diaphragm is diluted and the potential of the reference electrode is shifted. This will cause problems during ph measuring.
|Why does the zero point migrate over time?
||The position of the zero point depends on the ph value of the inner buffer. This can change because of loosened components of the glass. Also, a change of the KCl concentration shifts the potential of the reference electrode and therefore the zero point.