Low-Field NMR for the Online-Monitoring of Solid-Phase Peptide Synthesis -A first evaluation

Solid-phase peptide synthesis is a heterogenic process where the application of analytical methods for process control is difficult. Here, the low-field 1 H-NMR-technique is described as process-analytical technology (PAT) to be used for online-monitoring of solid-phase peptide synthesis. Both Fmoc-deprotection and coupling were investigated by 1 H-NMR as well as the subsequent washes of the resin. Initial experiments were conducted followed by the solid-phase synthesis of a small 5mer peptide amide. The 1 H-NMR measurements were accompanied by HPLC-investigations for the couplings and pH-measurements for the DMFwashes after Fmoc-deprotection. Especially the washing steps could be monitored successfully with this technique and with less accuracy also the coupling step. This PAT technique could be applied to feasibility studies to access new peptide sequences for upscaling in pilot plants on industrial scale.