We just received an interesting request from a customer and I thought the answer would be worth sharing. Most titrations are performed for pH only, in fact this is how the MPT (=Malvern pH Titrator) got its model name, and there are also additive linear, conductivity (additive log), and dilution methods available besides the standard pH titration. For ultimate flexibility there is yet another way to perform automated measurements:
Advanced titrations with three additive titrants
Specifically the question was: “Is there a way to vary the dosing of each of the titrants? I want to test 3 different coagulants and polymers as a mixture and vary the dose concentration for each run.” Yes, that is possible, however not via the standard titration interface. Use the SOP Player instead and the Inject Titrant command, where specific bottles can be selected, and in fact a whole arbitrary concentration sequence could be programmed and saved. To get to the SOP Player, select Measure – SOP Player from within the Zetasizer software (you can download the latest software) and then Inject Titrant. The volume to be injected can be specified in µL, and any of the titrant bottles can be selected as the source of the injection. In the screenshot below, 8 µL from the green titrant bottle will be injected into the sample. This can be followed by any number of additional injections, pauses, temperature changes,… The actual measurement is simply added as an SOP to the playlist. The whole playlist can be saved for reuse (or editing in case small changes in the titration experiment are desired).
For more details on how the titrator operates, as well as the standard pH, additive, conductivity, or dilution titrations, check out the titrator manual. Once the software is installed, this manual can be found under Start – All Programs – Malvern Instruments – Zetasizer – Documentation – Manuals – Manual: MPT-2 Titrator-Degasser User Manual (Man0318-4.0). Alternatively, this document can be downloaded from the website standalone, without the software.
Displaying individual titrants
The customer then continued: “It appears that the titrator dosing concentration is based on the sum total volume of all the titrants – is this right? In other words, is the Total Injected Volume reported by software calculated as the total volume dosed of Additive 1, Additive 2 and Additive 3.” Yes, in the default autotitration workspace the total injection volume in mL is displayed. Hoever this can easily be customized (check the main software manual, Start – All Programs – Malvern Instruments – Zetasizer – Documentation – Manuals – Man0485-1.1 Zetasizer Nano user manual) and any of the parameters desired can be added, since these are always recorded with the data set.
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