Finding pKa through microtitrations
We prepared a 0.2M solution of NaOH and Milli-Q water to use for titrating our 1% polymer solutions. Unfortunately not all of the polymers were dissolved when we arrived in the lab this morning so we only titrated P1(NG6), P2(NG6), P3(NG6), P4(NG6) and P8(NG6).
- Approximately 2g of NaOH pellets were weighed and put in a volumetric flask.
- The flask was filled up to the mark with Milli-Q water and labelled.
- A microburette was rinsed with Milli-Q water and filled with the 0.2M NaOH solution. The initial volume of the microburette was recorded.
- A vial of one of the fully dissolved 1% polymer solutions was opened and we tested the pH with a pH metre.
- The initial pH of the 1% polymer solution needed to be between 2.0-2.5 . If it wasn’t, 1 or 2 drops of HCl was added to bring the pH down.
- The 0.2M NaOH solution in the microburette was added drop-wise to the 1% polymer solution. After 1-3 drops each time, the pH of the 1% polymer solution was recorded and the volume on the microburette was noted down in a table.
- This was done until the pH of the 1% polymer solution reached over 11.00.
This titration method was repeated with all of the other 1% polymer solutions that had dissolved fully.
(Source: polymersomes)
