Introduction
Statistic copolymers of methyl methacrylate (MMA) and methacrylic acid (MAA) are used in pharmaceutical applications. The molar mass distribution, the chemical composition and the amount of comonomers are of importance. Characterization by gradient HPLC failed due to pronounced breakthrough peaks.
SEC-gradients has been successfully applied to measure the amount of MAA.
Procedure, Results & Discussion
The experimental procedure of SEC-gradients differs from conventional gradient HPLC. While in conventional HPLC the sample is dissolved in a weak eluent and injected at adsorbing conditions, the sample is dissolved in a strong mobile phase an injected at the end of the SECgradient. In the present application the copolymers were dissolved in DMAc. Gradient details:
- 0-3 min: 50%DMAc
- 3-8 min: 100%DMAc
- 8-23 min: 100%CHCl3
- 23-26 min: 5%DMAc
- 26-32 min: linear increase from 5% to 50% DMAc
Figure 1 shows the separation of 5 statistical MMA-MAA copolymers with MAA contents between 9 and 48%wt using a Chloroform/DMAc gradient from 5% to 50% DMAc. The sample components elute before the injected solvent and the different samples are clearly separated.
Fig. 1: Separation of 5 MMA-MAA copolymers with different PMMA content using a Chloroform - DMAc gradient on PSS PROTEEMA columns>> Download the full Application Note as PDF
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