A perspective on relative quantitation of a polydisperse polymer using chromatography and mass spectrometry

Abstract High throughput analysis of polymeric materials has become increasingly important in today's medical device industry. Direct matrix-assisted laser desorption ionisation (MALDI)-TOF MS analysis of polymers has been “the method of choice” for industrial analytical chemists due to its high speed, ease of use, and soft ionization. However, using this approach we experience difficulties for the analysis of poly(dimethyl siloxane) samples containing UV curable end groups. For example we observe a considerable amount of fragment products that act as chemical noise to the peaks of interest. This makes it difficult to obtain any meaningful quantitative information about the sample. In this study, we demonstrate that this dilemma can be remedied by coupling gel permeation chromatography (GPC) with MALDI-TOF MS analysis. With this approach a true impurity in the sample is clearly detected throughout the molecular weight distribution where direct analysis provided no information due to the chemical noise of the fragment peaks. This impurity is positively identified from exact mass measurements. The content of this impurity is calculated to be 33.0% by using a multiple data point approach from both GPC and MALDI-TOF analysis.