Seeking help with determining the endpoint in potentiometric titration
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As the title suggests, I am using a ZD-2A automatic potentiometric titrator. The problem now is that during titration, with each small addition of reagent, the increase in potential is not significant (around 2 to 3 mV), making it difficult to determine the end point of the titration. I would like to ask the experts here: are there any ways to increase the variation during titration, or other methods to make it easier to determine the endpoint?
If the titration reaction is rapid and involves a significant pH or potential shift, an indicator can be used to indicate the endpoint, which is more intuitive than potentiometric titration. By the way, what does “short drop” mean? Are there any long ones? If so, what are they?
Both short drops and long drops are functions provided by the titrator. A long drop means many drops in one go, while a short drop means one drop per press. Currently, the change in potential is not significant; it’s even less noticeable than that caused by an indicator. But I use potential actually to make the phenomenon more apparent; at present, I haven’t achieved this goal.
It wasn’t originally an increase in potential either； It’s used to determine the endpoint, right? Potentiometric titrators use the inflection point to do that. . It should start with long drops, and short drops should be used as it approaches the end. That’s right; you’re not familiar with this instrument, so I’m not sure if this can help you
It could be a problem with the electrode; it’s not sensitive anymore
There are generally two methods for determining the endpoint in potentiometric titration: 1. Equivalence point titration； 2. Endpoint titration. Generally, manufacturers should have set this up for you. For example, the former can be used in the determination of calcium ions, total hardness, chloride ions, etc., with the turning point of the potential value being used to determine the endpoint ； The latter can be used for measuring alkalinity and the like; simply set the endpoint pH value. In the situation you described, since it’s a short pulse, the change in potential value is naturally very small. If speed is required, then it should obviously be set to \"long pulse\". Lol; it’s up to the manufacturer to decide though – I’m just making an assumption. Different models of instruments use various names for many functions, but the principle remains the same. The potentiometric titrator I used before had a function called “pre-feed liquid,” whose purpose was to determine how many milliliters should be added at once. As for whether to choose potentiometric titration or manual titration, that is a matter for later consideration. After all, instrumental analysis is more convenient these days, but in some aspects its accuracy and reliability are not as good as those of chemical analysis; I think each method has its advantages and disadvantages. Since there’s a problem, just find a way to solve it. It is recommended to have in-depth discussions with the manufacturer and read the instructions carefully. :)Good luck~