MALDI-TOFMS of synthetic polymers as advanced high-throughput screening tool in combinatorial polymer chemistry

Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOFMS) is one of the most important MS techniques currently used for polymer anal. It is known to be a useful tool for the characterization of synthetic polymers in terms of abs. mol. wts., mol. wt. distributions and end-group anal. The most difficult part in MALDI anal. is the sample prepn., which is crucial for the success of the MALDI expt. Within this contribution, a new multiple-layer MALDI-TOFMS sample spotting technique is described. This fast and easy technique was evaluated with poly(ethylene glycol) (PEG) stds. and optimized conditions for these synthetic polymers were obtained. The spotting was performed using a multiple layer approach, which offers the capability of complex sample prepn. without the requirement of premixing the different matrix, analyte and doping salt solns. The technique reduces the time required for sample prepn. and offers high flexibility with respect to sample compn. and solvents utilized for the crystn. of the compds. The technique is thus perfectly suited for applications in combinatorial chem. and was implemented in the workflow of combinatorial polymer research. The technique can be performed utilizing a com. available synthetic robot and was first tested with polymer stds. of known compn. within the automated synthesizer and later on used for the monitoring of the living cationic ring-opening polymn. of 2-ethyl-2-oxazoline. The described technique reduces the time required for sample prepn. and offers the possibility of automated sample spotting during polymn. reactions performed in a synthetic robot. Moreover, the technique can be further automated by utilizing newly available ink-jet printing technologies. This allows fast and reproducible deposition of the required components (matrix/additive/polymer) onto the MALDI sample target and offers improved anal. possibilities for synthetic polymers. The described methods offer high flexibility, speed and reproducibility compared to conventional MALDI sample prepn. Therefore, the integration of MALDI-TOFMS as high-throughput tool into the workflow of combinatorial polymer research, becomes feasible